Journal of Refractive Surgery Vol. 24 No. 1 January 2008

Alexander Friedrich Scheuerle, MD; Michael Martin, MD; Hans Eberhard Voelcker, MD; Gerd Auffarth, MD


PURPOSE: To report a case of advanced glaucomatous optic atrophy years after bilateral radial keratotomy.


METHODS: Multiple intraocular pressure (IOP) measurements of both eyes in a 40-year-old woman who underwent previous bilateral radial keratotomy were obtained using Goldmann applanation tonometry as well as air-puff and Schiotz tonometry. In addition to regular eye examinations, corneal thickness, surface, and shape were examined using Orbscan and C-Scan.


RESULTS: The cornea of both eyes did not show signs of corneal thinning, but flattening of the corneal surface was observed. The decreased corneal curvatures precipitated a misjudgment of IOP readings measured by central applanantion tonometry (12 to 18 mmHg), whereas impression and non-contact tonometry revealed elevated IOP values (21 to 27 mmHg).


CONCLUSIONS: Changes of the corneal shape without corneal thinning can lead to falsely low IOP values. Therefore, in eyes that have undergone corneal refractive surgery, non-Goldmann measurement of IOP and continued examination of the optic nerve and possibly visual fields are recommended. [J Refract Surg. 2008;24:51-54.]

1: Ophthalmology. 2007 Jul 9; [Epub ahead of print]

Randleman JB, Woodward M, Lynn MJ, Stulting RD.

Department of Ophthalmology, Emory University, Atlanta, Georgia.; Emory Vision, Emory University, Atlanta, Georgia.



PURPOSE: To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence.


DESIGN: Retrospective comparative and case-control study.


PARTICIPANTS: All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors' institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course.


METHODS: Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia.


MAIN OUTCOME MEASURES: Development of postoperative corneal ectasia.


RESULTS: There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors' institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; P<1.0x10(-15)), were significantly younger (34.4 vs. 40.0 years; P<1.0x10(-7)), were more myopic (-8.53 vs. -5.09 diopters; P<1.0x10(-7)), had thinner corneas before surgery (521.0 vs. 546.5 mum; P<1.0x10(-7)), and had less RSB thickness (256.3 vs. 317.3 mum; P<1.0x10(-10)). Based on subgroup logistic regression analysis, abnormal topography was the most significant factor that discriminated cases from controls, followed by RSB thickness, age, and preoperative corneal thickness, in that order. A risk factor stratification scale was created, taking all recognized risk factors into account in a weighted fashion. This model had a specificity of 91% and a sensitivity of 96% in this series.


CONCLUSIONS: A quantitative method can be used to identify eyes at risk for developing ectasia after LASIK that, if validated, represents a significant improvement over current screening strategies.



This would suggest  that the 250 RSB rule is NOT safe. Why are they still using it and how are they getting away with it? This is an example of the LASIK industry ignoring medical literature and continuing to do business as usual, keeping the standard of care low and ignoring patients' best interest.

Spherical Aberration and Its Symptoms - Theories on why it occurs and how new technology may address the problem.

Spherical Aberrations - Spherical aberration is one of the most important problems that can occur after laser eye surgery, in particular with high myopic corrections.

Cataract & Refractive Surgery Today

June, 2007


According to a paper presented this month at the 6th International Congress on Advanced Surface Ablation and SBK, keratocytes' density decreases substantially in the anterior stroma of  refractive surgery patients during the first postoperative year and remains low for several years.1

William M. Bourne, MD, from the Mayo Clinic College of Medicine in Rochester, Minnesota, performed confocal microscopy on 34 eyes of 23 patients who underwent PRK or LASIK. At 7 years postoperatively, the density of keratocytes in the anterior stroma of PRK patients had dropped from 45,000 to 33,000 cells/mm², a total decrease of approximately 28%. He found a similar decrease (29%) in LASIK patients, whose keratocytes' density dropped from approximately 49,000 cells/mm² preoperatively to approximately 35,000 cells/mm² at 7 years postoperatively.

Because keratocytes secrete the collagen and proteoglycan necessary for the long-term maintenance of corneal clarity and curvature, the loss of these cells after refractive surgery may have long-term consequences for patients' corneal health, said Dr. Bourne. "We feel this possibility is unlikely, but cannot be ruled out," he added.


1. Bourne WM. The effect of PRK and LASIK on corneal keratocytes. Paper presented at: The 6th International Congress on Advanced Surface Ablation and SBK; May 5, 2007; Fort Lauderdale, FL.

Klin Monatsbl Augenheilkd. 2007; 224(5):438-40 (ISSN: 0023-2165)

Lautebach S; Funk J; Reinhard T; Pache M

Universitäts-Augenklinik Freiburg. This email address is being protected from spambots. You need JavaScript enabled to view it.



BACKGROUND: A steroid-induced glaucoma may develop after bilateral laser in situ keratomileusis (LASIK)  with normal intraocular pressure in applanation tonometry.


METHODS: We present the case of a 32-year-old patient who underwent bilateral LASIK for myopia. Postoperatively, a steroid-induced glaucoma developed. After the steroid therapy was stopped applanation tonometry showed normal values. A slight corneal opacity was interpreted as a keratokonjunctivitis sicca because of occupational noxa. One year after LASIK, the patient presented with high intraocular pressure (IOP), maximally excavated optic nerve head and extensive visual fields defect in both eyes.


CONCLUSION: Elevated IOP after LASIK can lead to fluid accumulation in the interface. In this case applanation tonometry can underestimate the intraocular pressure. Even when steroid therapy is stopped, the elevated pressure can persist.Steroid glaucoma after laser in situ keratomileusis - A steroid-induced glaucoma may develop after bilateral laser in situ keratomileusis (LASIK)  with normal intraocular pressure in applanation tonometry

Journal of Refractive Surgery Vol. 23 No. 6 June 2007

Sonal S. Tuli, MD; Sandhya Iyer, MD, FRCS



PURPOSE: To report a case of ectasia occurring >4 years following LASIK with no risk factors and a residual stromal bed >300 µm.


METHODS: A 33-year-old woman presented 4 years after LASIK with mild blurring in the left eye. Uncorrected visual acuity (UCVA) had been 20/20 in both eyes previously.


RESULTS: Uncorrected visual acuity was 20/20 and 20/40 in the right and left eyes, respectively. Best spectacle-corrected visual acuity (BSCVA) was 20/20 with –0.75 +2.25 X 70° refraction in the left eye, which matched topography. Preoperative corneal thickness was 595 µm, and topography showed no risk factors preoperatively or immediately postoperatively. Calculated residual stromal bed was 342 µm and measured 400 µm with ultrasound microscopy. One year postoperatively, UCVA decreased to 20/400, and BSCVA decreased to 20/60 with refraction of –4.50 +5.00 X 90°. The patient was intolerant of contact lens wear and is considering collagen cross-linking, Intacs, or corneal transplantation.


CONCLUSIONS: Ectasia can occur more than 4 years after LASIK. Its etiology is unknown and management is challenging. [J Refract Surg. 2007;23:620-622.]>



From the full text:

Quote: There was no documentation of intraoperative corneal thickness.

Quote: The posterior float on Orbscan increased to 55 μm (Fig 2). A Paradigm UBM microscope (Paradigm Medical Industries, Salt Lake City, Utah) was used to measure the residual stromal bed directly, which showed flap thickness of 150 μm and residual stromal bed of 400 μm.

Quote: This report shows that ectasia can occur >4 years following uncomplicated LASIK in a patient with no risk factors.

Quote: Confocal microscopy of corneas after LASIK have shown 20% loss of keratocytes above and below the flap interface by apoptosis immediately following surgery, which progressed to 40% at 5 years postoperatively.6 This loss of keratocytes has been seen in histology specimens of corneas removed during keratoplasty for ectasia.7 The decrease in keratocytes could progressively weaken the stromal bed and cause ectasia. It is conceivable that individual corneas differ in stromal keratocytes density, and the loss of keratocytes could cause ectasia in corneas with fewer keratocytes. Although most people develop ectasia much earlier, a weakened stromal bed may explain its development in our patient 4 years after LASIK.

Quote: Management of ectasia after LASIK is challenging due to its rapid progression. The use of contact lenses may correct vision but could be diffi cult to fi t, and patients may be intolerant due to dry eye, as was our patient.

Quote: One third of ectasia cases following LASIK require penetrating keratoplasty. 1 However, penetrating keratoplasty may result in unacceptable lifestyle changes in patients who often choose LASIK due to their active lifestyle. Also, a large graft may be necessary to include the entire LASIK flap and the donor cornea would be sutured to an intact recipient rim, which would increase risk of rejection. Other options are implantation of intrastromal rings (Intacs) and riboflavin with collagen cross-linking.8,9 However, these merely stabilize the cornea, and vision does not improve to the same levels noted before ectasia. In addition, cross-linking involves ultraviolet light, and its long-term effects are unknown.

Invest Ophthalmol Vis Sci. 2007 Jun;48(6):2570-5.

Rodriguez AE, Rodriguez-Prats JL, Hamdi IM, Galal A, Awadalla M, Alio JL.Vissum-Instituto Oftalmologico de Alicante, Alicante, Spain;



PURPOSE: To study the effect of the LASIK procedure performed with a femtosecond laser and a manual microkeratome on the conjunctival goblet cell and epithelial cell populations.


METHODS: In this prospective, nonrandomized, masked study, 64 eyes undergoing LASIK were included: 30 with the Moria M2 (M2) microkeratome and 34 with the IntraLase femtosecond laser (IL). The preoperative spherical equivalent was -2.0 +/- 3.8 D in the M2 group and -3.1+/- 3.1 D in the IL group. The time that the suction ring was applied on the eye was registered, and goblet cell density (GCD), epithelial cell morphology, and inflammatory cells were evaluated by conjunctival impression cytology, before and after the surgery.


RESULTS: All the patients in both groups showed a decrease in GCD after LASIK (P < 0.001) that recovered after 6 months. At 1 week, 1 month, and 3 months, GCD was lower with IL than with M2 (P < 0.019, P < 0.001, and P < 0.024, respectively). The mean period that the suction ring was applied was longer in the IL than in the M2 group (P < 0.001). There was a high correlation between the decrease in GCD and the suction time (R = 0., and the preoperative spherical equivalent (R congruent with 0.4).


CONCLUSIONS: Impression cytology showed a greater reduction in goblet cell populations after IL than after M2, probably because of the length of time that the suction ring exerted pressure on the conjunctiva. These changes in the goblet cells may contribute to the development of the ocular surface syndrome after LASIK procedures.

vs Hansatome microkeratome


J Refract Surg. 2007 Mar;23(3):305-7.

Ramirez M, Hernandez-Quintela E, Naranjo-Tackman R. Cornea and Refractive Surgery Services, Asociacion Para Evitar la Ceguera en Mexico, Hospital Luis Sanchez Bulnes, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico. This email address is being protected from spambots. You need JavaScript enabled to view it.



PURPOSE: To evaluate and compare confocal microscopy findings between a femtosecond laser and a mechanical microkeratome.


METHODS: Eighteen eyes of nine patients underwent LASIK. Corneal flaps were created with the femtosecond laser in the right eyes and a mechanical microkeratome in the left eyes. The corneal flap interface was analyzed in all eyes with a confocal microscope at 1 week and 1 month postoperatively.


RESULTS: All eyes showed small reflective particles at the corneal flap interface. The mean number of reflective particles was not statistically significantly different at 1 week (P = .078) and 1 month (P = .2 using a femtosecond laser and a mechanical microkeratome.


CONCLUSIONS: Confocal microscopy findings at the corneal flap interface showed a similar number of particles using both systems.


By Ilpo S. Tuisku, MD; Nina Lindbohm, MD, PhD; Steven E. Wilson, MD, PhD; Tim M. Tervo, MD, PhD



PURPOSE: To assess subjective symptoms and objective clinical signs of dry eye and investigate corneal sensitivity after high myopic LASIK.


METHODS: Twenty eyes of 20 patients with a mean age of 34±7.5 years who had undergone high myopic LASIK 2 to 5 years previously and 10 eyes of 10 controls with a mean age of 39.8±10.4 years were enrolled in the study. Clinical signs of dry eye and subjective dry eye symptoms were determined. The corneal sensitivity was assessed using non-contact esthesiometer.


RESULTS: The preoperative spherical equivalent refraction was –11.40±1.40 diopters (D) (range: –9.10 to –14.00 D) and the intended spherical equivalent refraction correction was –10.40±1.10 D (range: –8.30 to –12.50 D). Schirmer’s test score was 14.4±8.9 mm in patients and 9.0±4.2 mm in controls (P=.066). The break-up time was 15.9±11.2 seconds in patients and 14.0±10.0 seconds in controls (P=.505). The mean corneal sensitivity was 73.5±29.6 mL/min in patients and 78.0±18.7 mL/min in controls (P=.666). The majority (55%) of patients still reported dry eye symptoms. Ocular surface disease index indicating degree of dry eye symptoms was significantly higher in LASIK patients (18.6±13.4%) compared to controls (7.5±5.7%; P=.022).


CONCLUSIONS: The majority of patients who received LASIK for high myopia reported ongoing dry eye symptoms, although objective clinical signs of tear insufficiency and hypoesthesia were not demonstrable. We assume that symptoms represent a form of corneal neuropathy rather than dry eye syndrome. [J Refract Surg. 2007;23:338-342.]

Potential new post-laser refractive surgery complication identified



A new syndrome characterized by noninflammatory corneal opacification can occur in some patients within 9 days after undergoing LASIK or PRK, according to a study. The opacification gradually clears over several months and can also cause a possible hyperopic shift in refraction, the study authors said.

Baris Sonmez, MD, and Robert K. Maloney, MD, identified 23 eyes of 14 patients with the syndrome, which they termed central toxic keratopathy. Four eyes had undergone PRK and 19 eyes had undergone LASIK.

In all cases, eyes developed central corneal opacification in the laser-treated area 3 to 9 days after surgery, which persisted for 2 to 18 months, the authors reported. Eighteen of the 19 LASIK-treated eyes developed diffuse lamellar keratitis before the onset of the opacification, they noted.

Nine eyes also developed hyperopia over 2 D, one eye lost two lines of best corrected visual acuity, and two eyes lost one line, according to the study The hyperopia and residual striae can be treated with an enhancement procedure, but topical or oral corticosteroid treatment is not indicated, the authors noted.

The cause of the keratopathy is not known, they added.

The study is published in the March (2007) issue of the American Journal of Ophthalmology.


By Farid Karimian, MD; Alireza Baradaran-Rafii, MD; Mohammad Ali Javadi, MD; Roshanak Nazari, MD; Hossein Mohammad Rabei, MD; Mohammad- Reza Jafarinasab, MD



PURPOSE: To report clinical manifestations and the bacteriologic profiles of three patients with bilateral bacterial keratitis following photorefractive keratectomy (PRK).


METHODS: Photorefractive keratectomy was performed for mild to moderate myopia or compound myopic astigmatism. Bandage contact lenses were fitted at the conclusion of each surgery. Bilateral infectious keratitis was diagnosed within 3 days after surgery. Smear and culture were obtained in all three cases. Patients were treated with topical fortified antibiotics (cefazolin and gentamicin).


RESULTS: All patients presented with severe bilateral ocular pain, photophobia, purulent discharge, and dense corneal infiltration. Causative organisms were Staphylococcus aureus (n=2) and Streptococcus pneumoniae (n=1). Ulcers were controlled with aggressive medical therapy in five eyes; however, tectonic penetrating keratoplasty was required in one eye.


CONCLUSIONS: Uncontrolled blepharitis and bandage contact lens use appears to play a role in the development of bacterial keratitis after PRK. Avoidance of simultaneous bilateral surgery in patients with risk factors for bacterial keratitis, preoperative control of blepharitis, and good contact lens hygiene is suggested. [J Refract Surg. 2007;23:312-315.]


By Prashant Garg, MS; Savitri Sharma, MD; Geeta K. Vemuganti, MD; Balasubramanya Ramamurthy, MD



PURPOSE: To report a cluster of Nocardia asteroides keratitis cases after LASIK.


METHODS: Retrospective review of the history and examination of three patients (four eyes) operated on the same day at a single center who developed postoperative keratitis. All patients underwent lifting of the superficial flap for microbiologic evaluation of the corneal scrapings. The operating surgeon was contacted to identify the possible source of contamination.


RESULTS: Two patients underwent simultaneous bilateral LASIK; however, only one developed postoperative keratitis in both eyes. One patient had unilateral surgery and developed keratitis in the operated eye. Microscopic examination of smears from all eyes revealed thin, branching, acid-fast, filamentous bacteria that were identified as Nocardia asteroides after culture. The infiltrates resolved with topical administration of amikacin sulphate (2.5%) and topical and oral trimethoprim-sulfamethoxazole. Final visual acuity ranged between 20/25 and 20/80. The operating surgeon had used the same blade and microkeratome in all patients.


CONCLUSIONS: Nocardia, a relatively unusual organism, can cause an epidemic of infection after LASIK. [J Refract Surg. 2007;23:309-312.]

Due to Steroid-induced Elevation of Intraocular Pressure



By Joseph Frucht-Pery, MD; David Landau, MD; Frederik Raiskup, MD; Fiek Orucov, MD; Eyal Strassman, MD; Eytan Z. Blumenthal, MD; Abraham Solomon, MD



PURPOSE: To report the clinical course of early transient reduction of uncorrected visual acuity (UCVA) after LASIK surgery resulting from steroid-induced elevation of intraocular pressure (IOP).


METHODS: Twenty-nine eyes of 15 patients who received topical corticosteroids after uneventful myopic LASIK surgery and had a decrease in UCVA within the first 3 weeks were evaluated retrospectively.


RESULTS: Intraocular pressure increased by 4 to 30 mmHg from preoperative to postoperative days 4 to 20. Twenty-seven of 29 eyes had a decrease in UCVA and/or best spectacle-corrected visual acuity (BSCVA). All eyes, except one, had edema without evidence of inflammation in the interface or the remainder of the cornea. Discontinuation of topical corticosteroids and application of anti-glaucoma medications resulted in a decrease of IOP to normal levels, reduction or disappearance of the edema, and recovery of BSCVA.


CONCLUSIONS: Early onset steroid-induced elevation of IOP after LASIK may cause corneal edema and a sudden decrease in UCVA. Rapid diagnosis and treatment can control IOP and recover the visual loss. [J Refract
Surg. 2007;23:244-251.]

J Cataract Refract Surg. 2006 Dec;32(12):2075-2079.

Munoz G, Albarran-Diego C, Sakla HF, Javaloy J, Alio JL.

From the Refractive Surgery Department Centro de Especialidades Marques de Sotelo and Hospital NISA Virgen del Consuelo (Munoz, Albarran-Diego), Valencia, and the Refractive Surgery Department (Munoz, Sakla, Javaloy, Alio), VISSUM Instituto Oftalmologico de Alicante, Alicante, Spain.



PURPOSE: To describe the incidence of transient light-sensitivity syndrome (TLSS) after laser in situ keratomileusis (LASIK) with the femtosecond laser and to identify preventive strategies.


SETTING: Hospital NISA Virgen del Consuelo, Valencia, Spain.


METHODS: The first 765 eyes operated on with the 15 KHz femtosecond laser were prospectively analyzed for subjective complaints and clinical findings compatible with TLSS. Intraoperative settings, postoperative treatment, and development of complications were analyzed.


RESULTS: Overall, TLSS developed in 10 eyes (incidence 1.3%). However, the incidence decreased from 2.8% to 0.4% when aggressive topical steroids were used during the first 3 postoperative days. Postoperative interface inflammation and postoperative use of a low-dose topical steroid regimen were associated with a higher incidence of TLSS.


CONCLUSIONS: Transient light-sensitivity syndrome is a relatively uncommon complication related to the use of the femtosecond laser. Postoperative interface inflammation may increase the probability of developing TLSS, whereas an aggressive postoperative steroid regimen seemed to provide protection against it.

AJO, Vol 129, Issue 5 (May 2000) Pages 668-671

D. Matthew Bushley aA This email address is being protected from spambots. You need JavaScript enabled to view it., Vernon C. Parmley a and Patrick Paglen bet al.



PURPOSE: To report a case of visual field defect associated with laser in situ keratomileusis.


METHODS: Case report. A 28-year-old woman with high myopia (-10D) and a family history of normal tension glaucoma underwent bilateral laser in situ keratomileusis keratorefractive surgery. Preoperatively, both eyes had normal intraocular pressure and visual field.


RESULTS: At the first postoperative visit 1 day after apparently uncomplicated laser in situ keratomileusis, the patient reported a scotoma in the right eye. At 3-month follow-up, visual fields revealed the patient had developed a near-superior altitudinal visual field defect in the right eye. The defect did not progress over 1 year of follow-up examinations.


CONCLUSION: Increased intraocular pressure associated with the microkeratome vacuum ring used during laser in situ keratomileusis may have precipitated optic nerve head ischemia and visual field defect. eyes requiring cataract surgery: BESSt formula


J Cataract Refract Surg. 2006 Dec;32(12):2004-14.

Borasio E, Stevens J, Smith GT.

From the Moorfields Eye Hospital, London, United Kingdom.



PURPOSE: To describe a new formula, BESSt, to estimate true corneal power after keratorefractive surgery in eyes requiring cataract surgery.


SETTING: Moorfields Eye Hospital, London, United Kingdom.


METHODS: The BESSt formula, based on the Gaussian optics formula, was developed using data from 143 eyes that had keratorefractive surgery. The formula takes into account anterior and posterior corneal radii and pachymetry (Pentacam, Oculus) and does not require pre-keratorefractive surgery information. A software program was developed (BESSt Corneal Power Calculator), and corneal power was calculated in 13 eyes that had keratorefractive surgery and required cataract surgery.


RESULTS: In the eyes having phacoemulsification, target refractions calculated with the BESSt formula were statistically significantly closer to the postoperative manifest refraction (mean deviation 0.08 diopters [D] +/- 0.62 [SD]) than those calculated with other methods as follows: history technique (-0.07 +/- 1.92 D; P = .05); history technique with double-K adjustment (0.13 +/- 2.39 D; P = .05); Holladay 2 with K-values estimated with the contact lens method (-0.76 +/- 1.36 D; P = .03); Holladay 2 with K-values from Atlas topographer (Humphrey) (-0.55 +/- 0.61 D; P<.01). Using the BESSt formula, 46% of eyes were within +/-0.50 D of the intended refraction and 100% were within +/-1.00 D.


CONCLUSIONS: The BESSt formula was statistically significantly more accurate than the other techniques tested. Thus, it could significantly improve intraocular lens power calculation accuracy after keratorefractive surgery, especially when pre-refractive surgery data are unavailable.

Trans Am Ophthalmol Soc. 2005;103:56-66; discussion 67-8.

Erie JC, McLaren JW, Hodge DO, Bourne WM.

Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.



PURPOSE: To measure changes in keratocyte density up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).


METHODS: This was a prospective, nonrandomized clinical trial. Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 D, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 D. Corneas were examined by using confocal microscopy before and 6 months, 1 year, 2 years, 3 years, and 5 years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using Bonferroni-adjusted paired t tests.


RESULTS: After PRK, keratocyte density in the anterior stroma was decreased by 39%, 42%, 45%, and 47% at 6 months, 2 years, 3 years, and 5 years, respectively (P < .001). At 5 years, keratocyte density was decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap was decreased by 22% at 6 months (P < .02) and 37% at 5 years (P < .005). Keratocyte density in the anterior retroablation zone was decreased 18% (P < .005) at 1 year and 43% (P < .005) at 5 years. At 5 years, keratocyte density was decreased by 19% to 22% (P < .05) in the posterior stroma.


CONCLUSIONS: Keratocyte density is decreased in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK for up to 5 years. Posterior stromal keratocyte deficits are first noted at 5 years.


PURPOSE: To report a patient with a past history of LASIK who had decreased vision and induced corneal steepening after lower eyelid ptosis. Surgical correction of lower eyelid ptosis decreased the corneal steepening and improved visual acuity.


METHODS: Interventional case report. RESULTS: A 37-year-old woman had a history of bilateral LASIK, childhood strabismus surgery, and multiple surgeries to release scarring and improve motility in her left eye. Last surgery to release scar tissue resulted in reverse ptosis (lower eyelid ptosis) and decreased visual acuity from induced corneal steepening. Correction of lower eyelid ptosis by reinsertion of the retractor complex resulted in decreasing corneal steepening, improved visual acuity, and good anatomic position of the lower eyelid.


CONCLUSION: Lower eyelid ptosis may induce corneal steepening and decreased vision after LASIK.



Surgical correction of ptosis can decrease the extent of steepening and improve visual acuity.



Cataract Refract Surg. 2002 Mar;28(3):407-16.


Huang D, Arif M.


Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA. 



PURPOSE: To investigate the effect of laser spot size on the outcome of aberration correction with scanning laser corneal ablation.


SETTING: Cleveland Clinic Foundation, Cleveland, Ohio, USA.


METHODS: Corrections of wavefront aberrations of Zernike modes from the second to eighth order were simulated. Gaussian and top-hat beams of 0.6 to 2.0 mm full-width-half-maximum diameters were modeled. The fractional correction and secondary aberration (distortion) were evaluated.


RESULTS: Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, a 2.0 mm or smaller beam was adequate for spherocylindrical correction (Zernike second order), a 1.0 mm or smaller beam was adequate for correction of up to fourth-order Zernike modes, and a 0.6 mm or smaller beam was adequate for correction of up to sixth-order Zernike modes.



CONCLUSIONS: Since ocular aberrations above the Zernike fourth order are relatively insignificant in normal eyes, current scanning lasers with a beam diameter of 1.0 mm or less are theoretically capable of eliminating most higher-order aberrations.

Following Wavefront-guided and Conventional LASIK Surgery


Journal of Refractive Surgery  Vol. 22   No. 7   

September 2006 


Hyung Keun Lee, MD; Chul Myung Choe, MD; Kyoung Tak Ma, MD; Eung Kweon Kim, MD, PhD



PURPOSE: To compare contrast and glare vision in a prospective study of eyes treated using conventional and wavefront-guided LASIK surgery. The reproducibility of a glaremeter device used to quantitatively measure glare and halo was also determined.


METHODS: Ninety-two eyes of 46 patients underwent conventional LASIK surgery and 104 eyes of 52 patients underwent wavefront-guided LASIK surgery. Visual acuity, glare disability measured using a glaremeter, and contrast sensitivity assessed using a Pelli-Robson chart were measured monthly for 6 months postoperatively. Glaremeter testing was performed under both mesopic (5.4±0.4 cd/m2) and photopic (78.3±4.4 cd/m2) conditions. To evaluate the reproducibility of the glaremeter, 36 eyes of 18 nonoperated myopic patients were tested.


RESULTS: The coefficient of variation and the reliability coefficient for the glare test were 13.6% and 95.2%, respectively. The glaremeter showed that glare disability under mesopic conditions differed between conventional and wavefront-guided LASIK eyes over 6-month follow-up (907.5±491.5 vs 986.1±448.0 pixels preoperatively and 1717.1±521.2 vs 1407.8±411.3 pixels at 6 months, P<.0001). At 6 months, contrast sensitivity log values were 1.62±0.31 and 1.78±0.34 for conventional and wavefront-guided LASIK eyes, respectively (P=.010). The visual complaint score was lower in the wavefront-guided LASIK group (P=.0116).


CONCLUSIONS: Compared to conventional ablation, wavefront-guided ablation provided superior outcomes in terms of postoperative glare under mesopic conditions, subjective complaints, and contrast sensitivity. In addition, it appears the glaremeter can be used for clinical quantitative evaluation of glare and halo. [J Refract Surg. 2006;22:647-655.]

by Matt Young EyeWorld Staff Writer

The debate is growing with one laser squarely in the center.

Satisfied users of Alcon Inc.’s LADARVision excimer laser abound, but other surgeons are convinced retreatments were too frequent after they used the system.
LADARVision detractors cite a study published in the April 2003 edition of Ophthalmology as evidence that they’re right. The study, authored by Peter Hersh, M.D., an Alcon (Forth Worth, Texas) consultant concluded that “patients treated on the LADARVision laser had almost twice the rate of retreatment (18.2%) compared with the Summit Apex Plus laser (9.7%),” which is no longer manufactured.

Still, Dr. Hersh and others said that retreatment rates alone are so variable and so surgeon- and patient-dependent that it is unwise to lay blame on the LADARVision.

“There are hundreds of doctors around the world who use the LADARVision system and the vast majority of them are extremely satisfied with its performance,” said Doug MacHatton, Alcon's vice president of investor relations and strategic corporate communications. “Numerous peer-reviewed articles, as well as independent surveys of refractive lasers confirm that the LADARVision delivers excellent patient outcomes and that its enhancement rate is similar to other laser systems.”

Alcon headquarters in
Fort Worth, Texas. Source: Alcon

Mr. MacHatton noted that retreatment rates reported out of LADARVision's Food and Drug Administration (FDA) clinical trials range from 3% to 10%.
As for the 18.2% LADARVision retreatment rate that was published in Ophthalmology, Mr. MacHatton said, “Dr. Hersh’s analysis of the causes of enhancements are clearly supportive of Alcon’s position that retreatment rates or secondary procedures are primarily the result of variable patient healing, initial refractive error and complexity, practice of medicine decisions, and the many variables in any laser refractive procedure.” He also said the laser used in Dr. Hersh’s study was an earlier version of LADARVision before the upgrade to the company’s current LADARVision 4000.

Some surgeons—Mr. MacHatton and others note—retreat 20/20 eyes for higher patient satisfaction. Steven C. Schallhorn, M.D., director of cornea services,
Naval Medical Center, San Diego, who has analyzed LADARVision surgery for numerous studies, and Richard J. Mackool, M.D., Astoria, N.Y., an Alcon consultant who uses LADARVision extensively, noticed no problems with retreatments after using the excimer laser.

Others note that because LADARVision has the widest range of any laser, it is used for more extreme, difficult patient populations.
“Our retreatment rates are extremely low, and almost nonexistent, since we’ve gone to CustomCornea,” said Dr. Mackool, director, Mackool Eye Institute.

CustomCornea is Alcon’s wavefront-guided laser procedure using LADARVision.

While Dr. Mackool said his retreatment rates are actually less than the normal 8% to 10% range, “there may be a lot of people out there who have higher retreatment rates because they tackle more extreme refractive errors,” he said.

However, not everyone agrees.

Surgeons voice concerns

Sam Omar, M.D., medical director, Advanced Vision Institute,
Longwood, Fla., said after he did about 40 cases with LADARVision between 2000 and 2001, he stopped using the machine due to both a high retreatment rate and poor outcomes. He estimated that he enhanced about 20% of his LADARVision patients.

Source: Mackool Eye InstituteIn order to fix the problem, Dr. Omar said he modified his nomogram three times and worked with Alcon staff, but the problem remained unresolved.

“LADARVision at times would be spectacular,” Dr. Omar said. “Other times, the result would be a failure. You'll program in a +4 treatment on a patient who was +3 because you're making your nomogram adjustment, and after a month or two the patient would be +2.”
Other ophthalmologists also voiced serious concerns about LADARVision.

“While none of the multiple laser platforms I have used since 1996 is perfect, my experience with LADARVision was particularly troubling,” said Roy S. Rubinfeld, M.D., of Washington Eye Physicians & Surgeons, Chevy Chase, M.D. “I had several occasions where the thing would just stop working,” said Rubinfeld, who claimed his retreatment rate was at least 25% for two LADARVision machines used to perform a total of more than 1,000 cases from 2000 to 2002.

“I had one time where I had to put the flap back with a flashlight because the illumination light went off so I couldn’t figure out where the flap was,” Dr. Rubinfeld said. Undercorrections, overcorrections, astigmatism, and regression after LADARVision often prompted his retreatments, Dr. Rubinfeld said.

Study author defends LADARVision

While the retreatment rate associated with LADARVision was almost double that of the Summit Apex Plus in the study, Dr. Hersh concluded that “the difficulty of the initial procedures performed on the LADARVision laser, for example, higher degrees of astigmatism correction or mixed astigmatic corrections, compared with the Apex Plus laser, where more spherical myopic corrections were treated, may partially account for these findings.”

Furthermore, Dr. Hersh concluded that because the LADARVision was the newer machine in his practice, patient expectations could have been greater with the platform, causing more desire for enhancement. Later, during an e-mail exchange, Dr. Hersh said: “We did not at all concentrate on or design our methodology based on the difference between lasers. Thus, this is the wrong study from which to draw any conclusions regarding differences in retreatment rates between different systems.”

But other data—while not precise—suggest that retreatments after LADARVision can occur with abnormal frequency.

Data show high retreatment numbers

According to data presented under oath in a deposition, 27
U.S. surgical sites enhanced 20% or more primary LADARVision treatments from 2000 to 2002. That percentage is based on the ratio of all retreatments to all primary treatments recorded during that time frame. In 2002 alone, the data indicate that 55 sites had enhancement rates of 20% or greater, although sources familiar with the data noted that the enhancement rates could be somewhat off (either larger or smaller) depending upon whether some retreatments occurred at sites other than the original, occurred after primary treatments in previous years, or for other reasons.

In particular, AAPECS Eye Care (Virginia Beach, Va.) had retreatment rates of 17.8% in 2000, 18.1% in 2001, and 32.6% in 2002, according to the data.

“Before they came out with CustomCornea, I had significant retreatment rates,” said Ronald B. Frenkel, M.D., owner of AAPECS Eye Care. “But I’m a little bit different than most other people in that I would retreat a 20/20 eye. If someone came to me and they were unhappy with their vision and I could make it better, I did. But I still think my results were not as good as they should have been.”
He also questioned the 2002 retreatment rate listed for his clinic, noting that he has done many retreatments on patients whose primary treatments occurred in previous years.

“I still do probably two retreatments every two weeks, but none of them are on patients that I’ve done within the past year,” Dr. Frenkel said.
In fact, with CustomCornea, Dr. Frenkel said he has only retreated one patient.

Nine TLC Laser Eye Centers had LADARVision enhancement rates of 20% or greater in 2002, the data showed. A spokeswoman for TLC Laser Eye Centers, which she said has 70 clinics nationwide and uses LADARVision, said the company is not aware of any problems with the system's retreatment rates.
Alcon officials acknowledged that the data appear to be based on a document their company prepared in 2002 to summarize the number of primary and secondary procedures billed to customers. The officials contend that the document cannot be used to assess a laser's performance.

“In order to properly determine enhancement ratios for any laser or practice, it is necessary to know when the primary procedure was done, whether it was done on a different laser or by another doctor,” Mr. MacHatton wrote to EyeWorld. “In addition, comprehensive clinical data is needed on the pre- and post-operative assessment of patient populations. This would include the composition of high myopes, hyperopes, and patients with high levels of astigmatism or mixed astigmatism, the post-operative surgical results compared to the targeted ablation, and the enhancement philosophy of each physician.”

Source: Mackool Eye Institute“The referenced data….does not contain or rely on any of this information, so using it to analyze enhancements is completely invalid,” Mr. MacHatton wrote to EyeWorld.

Access to retreatment data

Alcon receives primary and secondary procedure data from all LADARVision 4000 machines for billing purposes, but surgeons contend it is not something they can readily retrieve from Alcon.

“Alcon refused to supply their billing information showing retreatment rates on our LADARVision laser after I requested that they do so,” said R. Doyle Stulting, M.D., Ph.D., professor of ophthalmology,
Emory University, Atlanta.

Officials at Alcon said the information is readily available to individual surgeons.

Alcon officials told EyeWorld that the information could not be used for clinical analysis because it is incomplete without surgical site data. They said they do send clinical teams to surgical sites if ophthalmologists suspect a problem with LADARVision.

A lawsuit, filed on behalf of EBW Laser Inc. (
Greensboro, N.C.) against Alcon in North Carolina, contends that underlying problems with LADARVision were intentionally concealed by Alcon. That lawsuit alleges that two LADARVision machines “suffered from unpredictable and erratic problems apparently caused by poor maintenance and repairs but aggravated by a design flaw in the machines that rendered the doctors using the machines unable to test their accuracy other than relying upon the machine’s own reports.” One system caused a retreatment rate of more than 50%, the lawsuit contends.

In an August letter to physicians, Bill Barton, vice president and general manager of Alcon’s surgical division, referred to the lawsuit allegations as “invalid contentions of parties who are attempting to avoid payment of multi-million dollar debts owed to Alcon.”

Meanwhile, the FDA has contacted at least one surgeon to request information about the performance of the LADARVision.

Everette Beers, Ph.D., the FDA’s chief of the diagnostic and surgical devices branch in the division of ophthalmic and ENT devices, declined to comment whether there is an investigation into LADARVision. While medical equipment manufacturers must report to the FDA any adverse effects that happen with unexpected severity or frequency, Dr. Beers said as long as patients don’t lose best corrected visual acuity, the FDA doesn’t necessarily consider retreatments adverse events.

Alcon officials said the company has not reported a high incidence of retreatments with any LADARVision system to the FDA because it hasn’t needed to do so.

“We haven’t identified any systemic issues that exist with the LADARVision 4000,” Mr. MacHatton said.

LADARVision was recalled twice in 2000 and 2001, and in many instances the same machines were recalled, according to two FDA enforcement reports. The reason for the 2000 recall, which applied to 136 units, was that patients had an “unsatisfactory vision correction due to error in ablation mask function.” The explanation for the 2001 recall, which affected 85 units, was that “unanticipated laser pulses reaching the cornea will cause ablation of the corneal surface, which could result in a central corneal defect of about 1 mm in diameter.”

Alcon officials note that no patients were injured on machines affected by the recalls.

Mixed views on retreatment

Whether or not higher retreatment rates have occurred because of an inherent LADARVision glitch, Alcon officials maintain retreatments generally are minor occurrences.

Similarly, Dr. Schallhorn doesn’t think retreatments are serious problems.

“Any time you have to lift the flap there’s a slight risk,” Dr. Schallhorn said. “I wouldn’t put it into a high-risk category.”
In his Ophthalmology study, Dr. Hersh mentioned that retreatments often do or don’t occur depending on patient’s subjective interpretation of what is visually satisfactory, reminding readers that “patient satisfaction, not emmetropia per se, is the essential goal of any refractive surgery procedure.”
Further confounding the issue of retreatment, Dr. Hersh said, is its definition. Some scientific literature even considers treating diffuse lamellar keratitis after LASIK a retreatment, he said.

Dr. Rubinfeld said he doesn’t consider retreatments just “touch-ups.”

“Additional risks occur with every surgical treatment and patients don’t want to be enhanced,” he said. “Whatever you can do to make your enhancement rate lower is good. You owe it to your patients.” 

Editors’ note: Drs. Omar, Schallhorn, Frenkel, Stulting and Rubinfeld have no financial interests related to their comments. Drs. Mackool and Hersh are consultants for Alcon.

Contact Information
Beers: 301-594-2018 ext 136, fax 301-827-4601, This email address is being protected from spambots. You need JavaScript enabled to view it.
Frenkel: 757-552-0800, fax 757-497-5900, This email address is being protected from spambots. You need JavaScript enabled to view it.
Hersh: 917-225-8965, 201-692-9646, This email address is being protected from spambots. You need JavaScript enabled to view it.
MacHatton: 817-551-8974, This email address is being protected from spambots. You need JavaScript enabled to view it.
Mackool: 718-728-3400, fax 718-728-4882, This email address is being protected from spambots. You need JavaScript enabled to view it.
Omar: 407-389-0800, fax 407-650-3400, This email address is being protected from spambots. You need JavaScript enabled to view it.
Rubinfeld: 301-654-5114, 301-654-9132, This email address is being protected from spambots. You need JavaScript enabled to view it.
Schallhorn: 619-532-6702, fax 619-532-7272, This email address is being protected from spambots. You need JavaScript enabled to view it.
Stulting: 404-778-6166, This email address is being protected from spambots. You need JavaScript enabled to view it.

Dan Z. Reinstein, MD, MA(Cantab), FRCSC, DABO



What differentiates the cornea from materials such as a contact lens? The cornea is an elastic collagen lamellar structure, the curvature of which is maintained firmly and constant by IOP. It is not difficult to imagine that differential thinning of the stroma can lead to differential bowing of the corneal layer producing central bulging.1 Additionally, the lamellar packing can be altered by the creation of a flap and tissue removal-the peripheral corneal lamellae adjacent to the keratectomized layer are no longer held tense and can relax, thus potentially causing a pull on the central cornea and causing central flattening.2 Finally, the epithelial thickness profile determines the majority of the final refractive power of the cornea, so changes in the profile of the epithelial layer can also cause changes in refraction.3

"Regression is reversion to an earlier condition or state." To illustrate this, imagine a myopic eye, undergoing LASIK for -4 D, that was found to be plano on postoperative day 1, -0.25 to 0.25x180 at 1 month, -0.75 at 3 months, 6 months, and 1 year. In this case, there was an initial correction of -4 D, which "regressed" to -0.75 D where it stabilized. Why did this case regress? Is it because the epithelium thickened in the center? Is it because the flap was too thick, and there was bowing of the central cornea forward?

For the purposes of this article, regression is defined narrowly to the observation of a shift in refraction postoperatively that tends to reverse the intended effect. The author is, therefore, excluding the situation where the refraction does not stabilize and continues to change due to plastic deformity of the cornea-a process known as keratectasia.4, 5 Differences among regression, primary undercorrection, and ectasia will now be illustrated.

If an eye was treated by LASIK for -8 D and on day 1, through to 1 week, 3 months, 6 months, and 1 year, the eye was found to be stable at -1 D, this would be defined as a primary undercorrection, rather than regression. If this same eye had been -0.75 D at postoperative day 1, -1.50 D at 1 month, -1.75 D at 3 months, but then stable through to 1 year, then the eye would have been said to have had a primary undercorrection of -0.75 D followed by regression from -0.75 to -1.75 D. It is important to differentiate between the causes of undercorrection because they point to the possible etiology and how to avoid keratectasia.

Primary undercorrection has many etiologies, but these can be divided into corneal and non-corneal causes. Non-corneal causes will include inaccurate preoperative refraction, inadequate laser energy delivery (eg, excess bed hydration, room humidity, inappropriate laser energy calibration, laser head energy instability). Corneal causes essentially include cases where the biomechanics of the cornea change due to the keratectomy and a stable but unpredicted curvature change is obtained. For example, this can happen if the residual stromal thickness was much less than 250 microns but not thin enough to cause long-term destabilization (ectasia). Examples of this will be shown.

For this tutorial, the author groups together both primary undercorrection for corneal causes (mostly biomechanical) and regression (mostly epithelial). The information and data that the author based this tutorial on contribute to ongoing studies to analyze the accuracy of LASIK with respect to epithelial and biomechanical changes. In this study, the author isolates and measures the effect of epithelial and biomechanical changes on the attempted corneal power change.

Fifty-two eyes that underwent routine LASIK between 1998 and 1999 with both the Moria LSK-One (Moria, Antony, France) and Hansatome (Bausch & Lomb, St Louis, Mo) microkeratomes, and with either the Nidek EC5000 (Nidek, Japan) or the B&L 217C (Bausch & Lomb) excimer laser6 were studied. Myopia from -1.00 to -10.25 D was included. Patients were scanned by 3D Artemis VHF digital ultrasound (Ultralink LLC,
St Petersburg, Fla) to obtain the thickness profile and optical power of the epithelium and stroma separately before and after LASIK. The author measured front and back surface curvature of the cornea using the Orbscan II (B&L, St. Louis, Mo) before and at least 3 months after LASIK. Epithelial thickness (ET) and residual stromal bed thickness (RST) 3D maps were produced from the Artemis data. The Orbscan determined the anterior and posterior corneal best-fit spheres (BFS).

Method for Isolating Epithelial and Biomechanical Changes

The curvature of Bowman's surface was calculated from the anterior BFS and the epithelial thickness profile from the Artemis. Gradient optics and lens formulae were used to calculate total corneal power from anterior, Bowman's, and posterior corneal interfaces. Back surface curvature change was defined as a bowing factor. The corneal power change (CPC) was calculated in this manner by comparing the preoperative and postoperative data. To isolate the effects of epithelial and biomechanical changes, the postoperative data were split into the following three permutations:

Epithelial factors: the bowing factor was removed by subtracting the back surface curvature change from each of the anterior, Bowman's, and posterior corneal surfaces.
Bowing factors: the epithelial factor was removed by substituting the postoperative epithelium for the preoperative epithelium.
Remove epithelial and bowing factors: the bowing factor was removed by substituting the postoperative back surface for the preoperative back surface and the epithelial factor was removed by substituting the postoperative epithelium for the preoperative epithelium.
Linear regression and paired t-tests were used to determine the epithelial and/or bowing contributions to the final refraction by correlating the attempted correction to the CPC.

General Observations

The author found that for the cohort of eyes, the minimum RST was 262 microns. Below an RST of 300 microns, postoperative back-surface curvature change correlated strongly with RST (R2=0.5). Attempted vs. achieved subjective refractive change was highly correlated (R2=0.95) with a slope of 0.92. CPC measurement by the calculation method was validated by a high correlation between change in clinical refraction and calculated CPC (R2=0.67, slope=0.90).

Isolating Epithelial and Bowing Factors

As described earlier, attempted correction was correlated with calculated CPC subtracting epithelial factors, bowing factors, and both epithelial and bowing factors. Removing epithelial changes gave a significant change in CPC and increased the slope to 0.94 (R2=0.66), whereas removing bowing gave a significant change in CPC and increased the slope to 0.99 (R2=0.46). Removing both epithelial and bowing factors resulted in a significant difference in CPC, with a correlation slope of 1.03 (R2=0.4, (all P<.01). This led to the conclusion that there were significant biomechanical and epithelial effects occurring, and that corneal elastic bowing and epithelium changes could practically account for the inaccuracy of LASIK.

In the magnitude analysis, mechanical changes accounted for a 15% decrease in intended reduction in central corneal power (P<.001). Epithelial changes accounted for a 5% decrease in intended reduction in central corneal power (P<.001). RST was correlated to the mechanical shifts calculated (R2=0.32). Ablation depth was highly correlated to the mechanical shifts observed (R2=0.89). Thickness of the stromal component of the flap significantly correlated with the spherical equivalent postoperative error (P<.05). Strong significant nonlinear correlations were found between the level of myopia treated and the epithelial (P<.001) or biomechanical (P=.011) power shift measured.

The Epithelium in Regression

The mean central epithelial thickness before surgery was 51 microns (range: 47-62 microns), whereas three months after LASIK, the central epithelium had thickened to an average of 61 microns (range: 44-75 microns). Central thickening amounts to a relative increase in curvature and, therefore, a regression in the myopic refractive effect of LASIK flattening.

In a raw comparison between the error in the postoperative spherical equivalent (all patients had an intended postoperative refractive error of zero) and the epithelial power shift as measured by Artemis scanning, the author found a statistically significant correlation. In other words, the postoperative refractive error could be (at least partly) accounted for by shifts in the power of the epithelium. The fact that these shifts were correlated alone is a testament to the significance of the epithelium in regression, considering the number of biomechanical factors that were also in play. A simple linear regression demonstrated a correlation in which for every diopter of postoperative spherical equivalent error, the epithelium could be accounting for about 25% of the error.

Plotting the level of myopia treated against the amount of epithelial thickening in the center and at the 3-, 4-, 5-, 6-, and 7-mm zones, a strong correlation between amount of epithelial thickening and the level of myopia treated was found. Two things stood out from this analysis. First, more thickening in the central cornea than the peripheral was found. Second, the epithelial thickening response was steep and linear for lower myopia, but appeared to level off as the level of myopia increased, which implies that the epithelium has the ability to reverse central flattening, but only to a certain extent.

To investigate further, the author divided the study eyes into three groups: low, moderate, and high myopia, and determined the thickening profile for each group separately.

The shift in power due to the epithelium will be related to the difference between central and peripheral thickening. For example, if the epithelium were to thicken evenly by 3 microns there would be no power shift (no change in curvature). For the low myopic group, there was considerably more thickening in the center than the periphery-8 microns versus 4 microns, and as myopia increased, the difference between the central and peripheral thickening diminished-in other words, the epithelium appears to be causing regression to a greater extent in lower myopia than higher myopia, despite the fact that there is less absolute thickening in lower myopia.

Thus, the shift in power due to epithelial profile changes was more significant for lower myopia than for higher myopia. Based on the central epithelial thickening reaching a maximum level beyond which increasing myopic ablation depth will not result in further central epithelial thickening while the peripheral epithelium can still thicken for higher myopic ablations as the peripheral ablation depth increases, the author has postulated a hypothesis to explain this shift.


Important nonlinear biomechanical and epithelial effects have been observed and characterized. Biomechanical changes appear well correlated to the residual stromal thickness, which is a function of the total amount of keratectomy, largely determined by the initial corneal thickness and flap thickness. Therefore, it follows that an accurate knowledge of the residual stromal thickness can be important when deciding to perform further enhancement surgery. Knowledge of the mechanical state of the cornea can be obtained by 3D residual stromal thickness mapping as provided by the Artemis. It is important to differentiate regression due to elastic and stable bowing of the cornea (more pronounced for thin residual stromal thickness) from regression due to epithelial changes (thick residual stroma). If the residual stromal thickness is low and responsible for mechanical changes, further tissue removal could, at best, produce an inaccurate result, but may unfortunately risk converting a stable elastic state into an unstable plastic corneal ectasia. This is particularly true of the newer wavefront-guided repair profiles, which aim to reduce spherical aberration and enlarge the optical zone, as they are very tissue intensive. In the final analysis, true customized ablation may require epithelial and biomechanical predictive modeling for achieving low aberration vision.


Seitz B, Torres F, Langenbucher A, Behrens A, Suarez E. Posterior corneal curvature changes after myopic laser in situ keratomileusis. Ophthalmology. 2001; 108:666-672; discussion 673.
Roberts C. The cornea is not a piece of plastic. J Refract Surg. 2000; 16:407-413.
Srivannaboon S, Reinstein DZ, Sutton HFS, Silverman RH, Coleman DJ. Effect of epithelial changes on refractive outcome in LASIK. Invest Ophthalmol Vis Sci. 1999; 40:S896.
Reinstein DZ, Srivannaboon S, Sutton HFS, Silverman RH, Shaikh A, Coleman DJ. Risk of Ectasia in LASIK: revised safety criteria. Invest Ophthalmol Vis Sci. 1999; 40:S403.
Barraquer JI. Queratomileusis y queratofakia.
Bogota: Instituto Barraquer de America; 1980.
Reinstein DZ, Srivannaboon S, Silverman RH, Coleman DJ. The accuracy of routine LASIK; isolation of biomechanical and epithelial factors. Invest Ophthalmol Vis Sci. 2000; 41:S318.

Question asked from a reader:

Dr. Dan Reinstein writes;

Quote: In the final analysis, true customized ablation may require epithelial and biomechanical predictive modeling for achieving low aberration vision.


Dr. Reinstein, as you know it is very rare for virgin eyes to have high levels of higher order aberration, central flattening, epithelial hyperplasia or excessive bowing. The changes you describe here are caused by an elective, medically unnecessary surgery. Now that you have identified these problems and realize that you can't prevent them, why on earth would you perform even one more surgery on a pair of healthy virgin eyes?

 American Journal of Ophthalmology
March, 1994  

Leo J. Maguire  




"To avoid aberration in the center of the visual field, the cornea must be regular over the entrance pupil".  

"When the cornea is irregular over the entrance pupil, the image generated by the cornea loses contrast and edge definition".  

"The final result is that corneal irregularity from refractive surgery can cause optical degradation; and optical performance in the central field can change with pupil size".  

"To avoid aberration in more peripheral portions of the visual field, the cornea must be regular over the cornea adjacent to the entrance pupil as well as over the entrance pupil itself."  

"First, the pupil enlarges. As it does, aberration of central vision increases as more distorted paracentral cornea falls within the pupillary space."  

"The problems with pupil-related aberration are further magnified by the reality that the Stiles-Crawford effect is negated in night vision."  

"I hope the reader will understand how a patient may have clinically acceptable 20/20 visual acuity in the daytime and still suffer from clinically dangerous visual aberration at night if that patient's visual system must cope with an altered refractive error, increased glare, poorer contrast discrimination, and preferentially degraded peripheral vision. People die at night in motor vehicle accidents four times as frequently as they do during the day, and these figures are adjusted for miles driven. Night driving presents a hazardous visual experience to adults without aberration. When we discuss aberration at night we are considering a possible morbid effect of refractive surgery."

Diffuse Lamellar Keratitis


J Refract Surg. 2006;22:441-447

Ahmed Galal, MD, PhD; Alberto Artola, MD, PhD; Jose Belda, MD, PhD; Jose Rodriguez-Prats, MD, PhD; Pascual Claramonte, MD, PhD; Antonio Sánchez, MD, PhD; Oscar Ruiz-Moreno, MD, PhD; Jesús Merayo, MD, PhD; Jorge Alió, MD, PhD


PURPOSE: To describe interface corneal edema secondary to steroid-induced elevation of intraocular pressure (IOP) following LASIK.

METHODS: Retrospective observational case series. Diffuse interface edema secondary to steroid-induced elevation of IOP was observed after LASIK simulating diffuse lamellar keratitis (DLK) in 13 eyes. Mean patient age was 31.4±5.3 years. Patients were divided into two groups according to provisional misdiagnosis: DLK group (group 1) comprised 11 eyes and infection group (group 2) comprised 2 eyes (microbial keratitis). Mean follow-up was 8.1±0.5 weeks.

RESULTS: In the DLK group, typical diffuse haze was confined to the interface and extended to the visual axis, impairing vision in all eyes. Provisional diagnosis was late-onset DLK and topical steroids were started. Repeat examination showed elevated IOP as measured at the corneal center and periphery using applanation tonometry (mean 19.1 mmHg and 39.5 mmHg, respectively), causing interface edema with evident interface fluid pockets. Steroids were stopped and topical anti-glaucoma therapy was started. The interface edema decreased and at the end of follow-up the corneal transparency was restored and IOP dropped to normal values. The infection group demonstrated a microbial keratitis-like reaction and underwent flap lifting and interface wound debridement and biopsy with administration of fortified antibiotics and steroids. After elevated IOP was detected, steroids and antibiotics were stopped and topical anti-glaucoma therapy was started, resulting in the resolution of the interface edema.

CONCLUSIONS: Interface fluid syndrome secondary to steroid-induced elevation of IOP might develop in steroid responders after LASIK with a misleading clinical picture simulating DLK or infectious keratitis. Management includes stopping topical steroids and starting topical anti-glaucoma therapy.

Cornea. 2006 May;25(4):388-403. 

Klein SR, Epstein RJ, Randleman JB, Stulting RD. 

From the *Cornea Service, Department of Ophthalmology, Rush University Medical Center, Chicago, IL; and the Department of Ophthalmology, Emory University Medical School, Atlanta, GA. 



PURPOSE:: To evaluate patients who developed ectasia with no apparent preoperative risk factors. 


METHODS:: Potential cases of patients who developed ectasia without apparent risk factors were identified by contacting participants in the Kera-Net (n = 580), ASCRS-Net (n = 450), and ISRS/AAO ISRS-Net (n = 525) internet bulletin boards from April to October 2003. Cases were included if ectasia developed after laser in situ keratomileusis in the absence of apparent preoperative risk factors. Reported cases were excluded for the following reasons: (1) calculated residual stromal bed less than 250 mum, (2) preoperative central pachymetry less than 500 mum, (3) any keratometry reading greater than 47.2 diopters (D), (4) a calculated inferior-superior value greater than 1.4, (5) more than 2 retreatments, (6) attempted initial correction greater than -12.00 D, (7) an Orbscan II "posterior float" (if obtained) greater than 50 mum, and (8) surgical/flap complications. 


RESULTS:: A total of 27 eyes of 25 patients were submitted for consideration. Eight eyes (8 patients) met our inclusion criteria. Mean age was 27.7 years (range, 18-41 years). Preoperative manifest refraction spherical equivalent was -4.61 D (range, -2.00 to -8.00 D); steepest keratometric reading was 43.86 D (range, 42.50-46.40 D); keratometric astigmatism was 0.93 D (range, 0.25-1.90 D); and preoperative central pachymetry was 537 mum (range, 505-560 mum). The mean calculated ablation depth was 82.8 mum (range, 21-125.4 mum), and mean calculated residual stromal bed was 299.5 mum (range, 254-373 mum). Mean time to recognition of ectasia onset was 14.2 months (range, 3-27 months) postoperatively. At the time of ectasia diagnosis, the mean manifest refraction spherical equivalent was -1.23 D (range, +0.125 to -3.00) with a mean of 2.72 D (range, 0.75-4.00 D) of astigmatism. 


CONCLUSIONS:: Ectasia can occur after an otherwise uncomplicated laser in situ keratomileusis procedure, even in the absence of apparent preoperative risk factors.

BMC Ophthalmol. 2006 Apr 28;6(1):19 

Dada T, Pangtey MS, Sharma N, Vajpayee RB, Jhanji V, Sethi HS. 





BACKGROUND: Diffuse lamellar keratitis (DLK) is a relatively new syndrome that is increasingly being reported after LASIK. We have observed that a hyperopic shift may be associated with the occurrence of this diffuse lamellar keratitis. 


CASE PRESENTATION: A 26 year old man developed bilateral diffuse lamellar keratitis (DLK) following myopic LASIK. The residual refractive error was +0.5D OD and +0.25D OS at the end of the first week. The sterile infiltrates resolved over a period of 4-6 weeks on topical steroid therapy. A progressive hyperopic shift was noted in the right eye with an error +4.25Dsph/+0.25Dcyl 20 at the final follow up 6 months post surgery. 


CONCLUSION: Diffuse lamellar keratitis after LASIK may be associated with a significant hyperopic shift.

 Cornea. 2006 Apr;25(3):291-5.

Yeung L, Chen YF, Lin KK, Huang SC, Hsiao CH.

Department of Ophthalmology, Chang Gung Memorial Hospital, Taipei, Taiwan, ROC.


PURPOSE: To describe central corneal iron deposition after myopic LASIK.

METHODS: Patients visiting our outpatient clinics between February 2003 and January 2004 and displaying post-LASIK corneal iron deposits were retrospectively enrolled in the study.

RESULTS: Forty-two eyes of 24 patients developed corneal iron deposition after myopic LASIK surgery. All eyes displayed a small, spotty iron deposit located in the center of the corneal flap. The median interval between LASIK and diagnosis of corneal iron deposition was 22.5 months. The spherical equivalents of achieved correction ranged from 4.00 D to 17.50 D.

CONCLUSION: Spotty corneal iron deposition can develop in the center of the corneal flap after myopic LASIK surgery. Because it is asymptomatic, the condition may have been hitherto underestimated in patient populations.

From website:

Spherical aberration is one of the most important problems that can occur after laser eye surgery, in particular with high myopic corrections.

For lenses made with spherical surfaces, rays which are parallel to the optic axis but at different distances from the optic axis fail to converge to the same point. The peripheral light rays are bent more than the central ones as in the following diagram:

A spherical surface has a "Q value" of 0. A surface which is a parabola has the peripheral part of the lens relatively flatter than the centre and so bends the peripheral light rays less, eliminating this spherical aberration. Such a cornea has a negative Q value and has a prolate shape A parabola has a Q value of -0.5. The human eye of a young person has a Q value of -0.5, which is made up of the cornea (Q= -0.25) and the lens of the eye (Q= -0.25) added up together. The over 40y age group has a rounding out of the lens, so its Q value becomes near O. Hence older people have more natural spherical aberration as their Q value is only that of the cornea i.e. -0.25.

There is a nice demonstration of spherical aberration at the
Olympus web site ( The Hubble Space Telescope suffered from spherical aberration when first launched. This was solved by using "adaptive optics", similar to that now being used in excimer lasers. See the Hubble page on this web site:

After a myopic PRK or LASIK, the Q value becomes positive with increased spherical aberration. The cornea then has an oblate shape No normal human cornea is oblate or has a positive Q value. However, all the modern lasers have "blend zones" that smooth off the mid-peripheral "knee" that has a high local Q value and this lessens the induced spherical aberration. e.g. The Technolas 217 laser has true optical zones up to 7mm with a blend zone at least 3mm bigger than this. (the cornea is only about 12.5mm diameter). Similarly the Nidek EC5000 has optical zone up to 6.5mm and the blend zone is adjustable up to 10mm.

Spherical aberration is not really a problem with low myopic corrections but can be a problem with some patients having higher corrections e.g. about about -5 D. The laser manufacturers are tying to improve the shape of the ablation profile to lessen this problem. All the "custom ablations" done by various lasers have totally "aspheric" profiles that have, in theory, no aberrations. However, they can take off more tissue, which can again be a problem with higher corrections as there may not be much to spare. Spherical aberration is not normally a problem in good light but in low light. See night vision: ( and lasik complications:

 J Refract Surg. 2006 Mar;22(3):309-12. Related Articles, Links  

Ramos-Esteban JC, Servat JJ, Tauber S, Bia F.  

Department of Ophthalmology, Yale University School of Medicine, New Haven, Conn, USA 

PURPOSE: To report the history and clinical presentation of a 23-year-old man who developed delayed onset lamellar keratitis in his right eye 2 weeks after uneventful LASIK for correction of myopia.

METHODS: Initial clinical presentation suggested an infectious etiology, which led to therapeutic elevation of the LASIK flap and further microbiologic investigation with bacterial cultures.

RESULTS: Bacterial cultures revealed Bacillus megaterium, which was sensitive to all antibiotics against which it was tested. Twenty-four hours after initiating aggressive topical and oral antibiotic therapy, symptomatic relief occurred in the affected eye. The patient's uncorrected final visual acuity at 1-year follow-up was 20/15 in the right eye, and the stromal bed developed a faint peripheral non-visually significant scar.

CONCLUSIONS: This case is an unusual presentation and course for microbial keratitis following LASIK, which occurred despite aseptic technique and fluoroquinolone antibiotic prophylaxis. Following refractive surgery one should be prepared to culture the lamellar interface in cases of suspected microbial keratitis and begin aggressive antibiotic therapy.

J Cataract Refract Surg 2003; 29:257–263

Michael Bueeler, MSE, Michael Mrochen, PhD, Theo Seiler, MD 

Purpose: To investigate the lateral alignment accuracy needed in wavefront-guided refractive surgery to improve the ocular optics to a desired level in a percentage of normally aberrated eyes.  

Setting: Department of Ophthalmology, University of Zurich, Zurich, Switzerland 

Methods: The effect of laterally misaligned ablations on the optical outcome was simulated using measured wavefront aberration patterns from 130 normal eyes. The calculations were done for 3.0 mm, 5.0 mm, and 7.0 mm pupils. The optical quality of the simulated correction was rated by means of the root-mean-square residual wavefront error.  

Results: To achieve the diffraction limit in 95% of the normal eyes with a 7.0 mm pupil, a lateral alignment accuracy of 0.07 mm or better was required. An accuracy of 0.2 mm was sufficient to reach the same goal with a 3.0 mm pupil.  

Conclusion: Procedures must be developed to ensure that the ablation is within a tolerance range based on each eye's original optical error. Rough centration based on the surgeon's judgment might not be accurate enough to achieve significantly improved optical quality in a high percentage of treated eyes.

J Cataract Refract Surg 2003; 29:250–256

Joseph K.W. Hsu, MD, W. Todd Johnston, MD, Russell W. Read, MD, Peter J. McDonnell, MD, Rey Pangalinan, MD, Narsing Rao, MD Ronald E. Smith, MD 

Purpose: To describe the histopathology of the cornea in 3 cases of corneal melting associated with diclofenac therapy after refractive surgery procedures.  

Setting: Clinic and pathology laboratory.  

Methods: Three cases of corneal melting associated with diclofenac therapy (2 after laser in situ keratomileusis [LASIK] and 1 after mini-radial keratectomy enhancement of a LASIK undercorrection) were studied using patient and referring physician interviews, chart reviews, and histopathologic examination of the corneal tissue.  

Results: In all 3 cases, the flaps were dislocated and the stromal corneal bed was exposed. Diclofenac, generic or brand name, was used in all cases; in 1 case, both generic and brand name were used. Dosing and duration varied, but in all 3 cases diclofenac was used at least 4 times a day for at least 3 days after LASIK. Topical steroids were also prescribed, but 1 patient did not use them. Preoperative medical conditions were present in 2 cases. Histologic analysis showed evidence of an inflammatory response in advanced cases and keratolysis and lack of inflammatory cells in the flaps that were amputated early.  

Conclusions: The use of generic or brand-name diclofenac with or without adjunctive topical steroids after LASIK can be associated with corneal melting when the LASIK flap is dislodged and the corneal stromal bed exposed. Caution is recommended with diclofenac use after LASIK in such cases.

J Cataract Refract Surg 2003; 29:133–137

Dimitrios S. Siganos, MD, PhD, Corina Popescu, MD, Nikolaos Bessis, DOpt, Georgios Papastergiou, MD 

Purpose: To correlate cycloplegic subjective refraction with cycloplegic autorefractometry in eyes that have had LASIK.  

Setting: Vlemma Eye Institute, Athens, Greece 

Methods: Subjective refraction and autorefractometry under cycloplegia were performed in 73 eyes of 46 patients 1, 6, and 12 months after LASIK to correct myopia or myopic astigmatism. The preoperative subjective refraction and autorefractometry under cycloplegia in the same eyes served as controls.    

Results: A statistically significant difference between subjective refraction and autorefraction was found in the sphere and cylinder at all postoperative times. No statistically significant difference was found in the axis. There was no statistically significant difference in the control eyes.  

Conclusions: Automated refractometry in eyes that had had LASIK was reliable in the axis only. Retreatments after LASIK should always be based on subjective refraction.  

J Cataract Refract Surg 2003; 29:118–124

Jay W.W. Chan, MPhil, Marion H. Edwards, PhD, George C. Woo, OD, PhD, Victor C.P. Woo, MD 

Purpose: To develop, evaluate, and use an objective method to determine the effect of LASIK on corneal clarity.  

Setting: Centre for Myopia Research, The Hong Kong Polytechnic University, and the Hong Kong Laser Eye Center, Hong Kong, China 

Methods: Color  photographs of corneal sections were taken using a digital camera and converted to 8-bit gray-scale images. The desired area of the photograph was isolated using a preset mask, and a gray-scale or corneal clarity index of the desired area was obtained by averaging the “intensity” indices of individual pixels within the area. The reliability of the clarity index measures was determined by comparing test and retest measures. The sensitivity of the method was quantified by its ability to identify a small (clinically undetectable) decrease in corneal clarity produced by tight-fitting soft contact lenses worn for 30 minutes. Finally, corneal clarity was measured and compared in 24 patients before and 1 day, 1 week, and 1 month after LASIK.  

Results: The reliability value was 4.11 corneal clarity units, and the change in corneal clarity due to soft contact lens use was 16.24 units. In the LASIK patients, there were statistically significant decreases in corneal clarity from preoperatively to 1 day and 1 week but not to 1 month.  

Conclusions: The method measured changes in corneal clarity that were undetectable clinically and were 4 times greater than 95% of the differences between test and retest measures. The method is therefore reliable and sensitive. Corneal clarity decreased after LASIK and recovered within approximately 1 month.

J Cataract Refract Surg 2002; 28:2088–2095

Francesco Carones, MD, Luca Vigo, MD, Elena Scandola, MD, Letizia Vacchini, MD 

Purpose: To evaluate the results of the prophylactic use of mitomycin-C to inhibit haze formation after excimer laser photorefractive keratectomy (PRK) for medium and high myopia in eyes that were not good candidates for laser in situ keratomileusis (LASIK).   Setting: Carones Ophthalmology Center, Milan, Italy 

Methods: This prospective randomized masked study comprised 60 consecutive eyes (60 patients). The inclusion criteria were a spherical equivalent correction between −6.00 and −10.00 diopters (D) and inadequate corneal thickness to allow a LASIK procedure with a residual stromal thickness of more than 250 μm. The eyes were divided into 2 groups according to the randomization protocol. After PRK, the study group eyes were treated with a single intraoperative dose of mitomycin-C (0.2 mg/mL), applied topically with a soaked microsponge placed over the ablated area and maintained for 2 minutes. The control eyes did not receive this treatment. Refraction, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and slitlamp evidence of corneal opacity (haze) or other visible complications were evaluated.   Results: No toxic or side effects were encountered postoperatively. No study group eye had a haze rate higher than 1 during the 6-month follow-up; 19 eyes (63%) in the control group did (P = .01). At 6 months, the between-group difference in the refractive outcome was statistically significant (P = .05), with 26 study group eyes (87%) and 14 control eyes (47%) within ±0.50 D of the attempted correction. No study group eye had a BCVA loss during the follow-up; 7 control eyes had lost 1 to 3 lines at 6 months (P = .0006).  

Conclusion: The prophylactic use of a diluted mitomycin-C 0.02% solution applied intraoperatively in a single dose after PRK produced lower haze rates, better UCVA and BCVA results, and more accurate refractive outcomes than those achieved in the control group.  

Cornea. 2005 Jul;24(5):509-22.  

Netto MV, Mohan RR, Ambrosio R Jr, Hutcheon AE, Zieske JD, Wilson SE.  The Cole Eye Institute, The Cleveland Clinic Foundation, OH 44195, USA 

PURPOSE: The corneal wound healing response is of particular relevance for refractive surgical procedures since it is a major determinant of efficacy and safety. The purpose of this review is to provide an overview of the healing response in refractive surgery procedures.  

METHODS: Literature review.  

RESULTS: LASIK and PRK are the most common refractive procedures; however, alternative techniques, including LASEK, PRK with mitomycin C, and Epi-LASIK, have been developed in an attempt to overcome common complications. Clinical outcomes and a number of common complications are directly related to the healing process and the unpredictable nature of the associated corneal cellular response. These complications include overcorrection, undercorrection, regression, corneal stroma opacification, and many other side effects that have their roots in the biologic response to surgery. The corneal epithelium, stroma, nerves, inflammatory cells, and lacrimal glands are the main tissues and organs involved in the wound healing response to corneal surgical procedures. Complex cellular interactions mediated by cytokines and growth factors occur among the cells of the cornea, resulting in a highly variable biologic response. Among the best characterized processes are keratocyte apoptosis, keratocyte necrosis, keratocyte proliferation, migration of inflammatory cells, and myofibroblast generation. These cellular interactions are involved in extracellular matrix reorganization, stromal remodeling, wound contraction, and several other responses to surgical injury.  

CONCLUSIONS: A better understanding of the complete cascade of events involved in the corneal wound healing process and anomalies that lead to complications is critical to improve the efficacy and safety of refractive surgical procedures. Recent advances in understanding the biologic and molecular processes that contribute to the healing response bring hope that safe and effective pharmacologic modulators of the corneal wound healing response may soon be developed 

From the conclusion:  

Wouldn't you think they'd want to figure this out before performing refractive surgeons on millions and millions of patients?

J Cataract Refract Surg. 2005 Dec;31(12):2356-62. 

Brown SM, Freedman KA.  Cabarrus Eye Center, Concord, North Carolina 28025, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.  

PURPOSE: To determine whether the currently accepted method of selecting a minimum optical zone diameter for laser refractive surgery that is equal to or slightly greater than the dark-adapted pupil diameter provides a sufficient diameter of corneal surface to focus light arising from objects in the paracentral and peripheral visual field.  

SETTING: Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA 

METHODS: An optical model of the anterior segment was developed to calculate the effective corneal refractive diameter (ECRD), which is the diameter of the area of cornea that refracts all incident light rays arising from an object through the physical pupil (PP). This model incorporates the patient variables of central anterior chamber depth (ACD), central corneal curvature (K(c)), and the diameter of the apparent entrance pupil (EP). The model was expanded to incorporate distant objects off the line of sight (LOS), described by their angular displacement from the fixation object in visual space (the object tangent angle delta(ob)). Results were calculated for the 360 meridian degree visual field (ie, for all objects in visual space perceptually displaced from the fixation object by angle delta(ob)). The effect of the prolate nature of the cornea was also investigated.  

RESULTS: The ECRD expanded rapidly as a function of PP and delta(ob) but was minimally influenced by K(c). Beyond a critical object tangent angle delta(c), light rays striking the corneal vertex were not refracted through the PP, and the ECRD became an annular surface centered on the corneal vertex. The delta(c) was not a function of K, but increased as the PP increased and decreased as the ACD increased. The prolate nature of the cornea had little influence on the ECRD, even for very peripheral light rays.  

CONCLUSIONS: The ECRD expands rapidly when considering distant objects only slightly displaced from the LOS. A patient treated with an optical zone equal to or slightly greater than the dark-adapted pupil diameter may experience vision quality loss for paracentral and midperipheral objects even under conditions of ambient indoor lighting.

This seems like what everyone is saying about LASIK. But who is Sandra Brown, and what happened in the case?

Am J Ophthalmol. 2006 Mar 15;  

Erie JC, Patel SV, McLaren JW, Hodge DO, Bourne WM.  Department of Ophthalmology (J.C.E., S.V.P., J.W.M., W.M.B.).  

PURPOSE: To measure changes in keratocyte density up to 5 years after PRK and LASIK.  

DESIGN: Prospective, nonrandomized clinical trial.  

METHODS: Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 diopters, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. Corneas were examined by using confocal microscopy before and 6 months, 1 year, 2 years, 3 years, and 5 years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using paired t tests with Bonferroni correction for five comparisons.  

RESULTS: After PRK, keratocyte density in the anterior stroma decreased by 40%, 42%, 45%, and 47% at 6 months, 2 years, 3 years, and 5 years, respectively (P < .001). At 5 years, keratocyte density decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap decreased by 22% at 6 months (P < .02) and 37% at 5 years (P < .001). Keratocyte density in the anterior retroablation zone decreased by 18% (P < .001) at 1 year and 42% (P < .001) at 5 years. At 5 years, keratocyte density decreased by 19% to 22% (P < .05) in the posterior stroma.  

CONCLUSIONS: Keratocyte density decreases for at least 5 years in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK.


Surv Ophthalmol. 2005 May-Jun;50(3):245-51.  

Comment in: Surv Ophthalmol. 2005 Nov-Dec;50(6):611-2; author reply 612.  

Bashford KP, Shafranov G, Tauber S, Shields MB.  Department of Ophthalmology and Visual Sciences, Yale University School of Medicine, New Haven, Connecticut; and Glaucoma Consultants of Colorado, P.C., Littleton, Colorado, USA.  

Glaucoma patients present a unique set of challenges to physicians performing corneal refractive surgery. Corneal thickness, which is modified during corneal refractive surgery, plays an important role in monitoring glaucoma patients because of its effect on the measured intraocular pressure. Patients undergo a transient but significant rise in intraocular pressure during the laser-assisted in situ keratomileusis (LASIK) procedure with risk of further optic nerve damage or retinal vein occlusion. Glaucoma patients with filtering blebs are also at risk of damage to the bleb by the suction ring. Steroids, typically used after refractive surgery, can increase intraocular pressure in steroid responders, which is more prevalent among glaucoma patients. Flap interface fluid after LASIK, causing an artificially low pressure reading and masking an elevated pressure has been reported. The refractive surgeon's awareness of these potential complications and challenges will better prepare them for proper management of glaucoma patients who request corneal refractive surgery.

Using Noncontact Tonometry in Patients After Myopic LASIK Surgery  

Cornea. 2006 Jan;25(1):26-28.  

Cheng AC, Fan D, Tang E, Lam DS.  

PURPOSE:: To evaluate the effect of corneal curvature and corneal thickness on the assessment of intraocular pressure (IOP) using noncontact tonometry (NCT) in patients after myopic LASIK surgery.  

METHODS:: All patients who had myopic LASIK in a university-based eye clinic between February 2002 and May 2002 were retrospectively analyzed. Preoperative NCT was compared with postoperative NCT, postoperative corneal thickness, and postoperative corneal curvature.  

RESULTS:: The difference between the mean preoperative NCT (15.46 +/- 2.50 mm Hg) and postoperative NCT (6.30 +/- 1.57 mm Hg) was significant (9.16 +/- 1.96 mm Hg, P < 0.010). Preoperative NCT significantly correlated with postoperative NCT (P < 0.001), postoperative corneal thickness (P = 0.006), and postoperative anterior corneal curvature (P < 0.010).  

CONCLUSIONS:: Both corneal thickness and anterior corneal curvature affect IOP assessment in patients with myopic LASIK. Although correction formulas can be used to estimate the actual IOP, alternative methods should be investigated to assess IOP independent of corneal thickness and curvature.  

"Our model can account for only 47% of the variability in the actual postoperative IOP." 


Excerpts from the full text of the article that was posted above:  

"Laser in situ keratomileusis (LASIK) has gained popularity over recent decades and become a widely accepted type of corneal refractive surgery. During myopic LASIK, corneal stromal ablation with the excimer laser results in reduced corneal thickness and curvature. Such changes affect the measurement of intraocular pressure (IOP).1-6 

Noncontact pneumatic tonometry (NCT) is a simple and safe device for routine IOP measurements. Previous data have shown that NCT can produce accurate IOP assessment comparable to Goldmann tonometry,7-9 which is the gold standard. However, NCT has been shown to underestimate IOP measurements in patients with myopic LASIK in various studies,1-6 and different methods have been proposed to determine the actual IOP.10-13 

Before a better device can be designed, it is important to identify the factors that cause the underestimation in LASIK patients. Although numerous studies have shown that corneal thickness plays an important role,4-9 the effect of corneal curvature is not conclusive.4-9"  

"In a busy refractive clinic, NCT has become a very effective screening tool for the assessment of IOP. However, it has also been shown to underestimate IOP in patients with myopic LASIK.4-8 Therefore, it is important to know the effect of LASIK on IOP measurement by NCT.  

In myopic LASIK, the corneal thickness is reduced. With less corneal tissue producing counterpressure, less force is required to deform the cornea. At the same time, myopic LASIK also flattens the cornea. With a flatter cornea, the anterior corneal surface does not need to deform as much to reach the applanation area.

Although many studies found the association of corneal thickness with manifest IOP,5,10,12,14,15 the results of the association between the IOP and corneal curvature are conflicting.7,9,13,16-20 One of the reasons is that previous studies used the direct keratometry reading obtained from corneal topography or keratometer for the assessment. However, direct keratometry readings from the device are known to be inaccurate in patients after corneal refractive surgery like LASIK.21,22  

With existing keratometers and videokeratoscopes, the radius of curvature of the anterior corneal surface is what is actually measured. The keratometric diopters are derived form radius of curvature using an effective refractive index in a paraxial formula where K = (n - 1)/r. The refractive index between air and the anterior corneal surface is 1.376. Therefore, the refractive power of the anterior corneal surface should be 0.376/r. However, these devices are calibrated to give the true corneal power. The assessment of the true corneal power is based on the assumption that the relationship between the anterior and posterior curvature and the distance between them is a constant. Based on the Gullstrand eye model, the 2 refracting surfaces can be considered as 1 with a fictitious single refractive index of 1.3375. This is the refractive index that most keratometers and videokeratoscopes use.23  

After refractive surgery, the basic assumption no longer holds because the anterior corneal curvature changes and the posterior curvature remains constant. The distance between the 2 refractive surfaces is also significantly reduced. Therefore, the basic assumption of the Gullstrand eye model is no longer valid. The direct keratometry readings from these devices are therefore inaccurate."

...and their impact on intraocular pressure measurements.

Graefes Arch Clin Exp Ophthalmol. 2005 Dec;243(12):1218-20. Epub 2005 Jul 8.

Svedberg H, Chen E, Hamberg-Nystrom H.

St Erik's Eye Hospital, Karolinska Institutet, Polhemsgatan 50, 112 82, Stockholm, Sweden, This email address is being protected from spambots. You need JavaScript enabled to view it..

BACKGROUND: Excimer laser refractive surgery alters the shape and thickness of the cornea by removing central corneal tissue with submicrometer precision. The aim of the study was to analyze the changes in central corneal thickness (CCT) and curvature before and after different excimer laser photorefractive procedures and their possible impact on intraocular pressure (IOP) estimations with Goldmann applanation tonometry.

METHODS: Data on CCT, corneal curvature and IOP readings with Goldmann applanation tonometry before and after excimer laser photorefractive surgery were analyzed retrospectively. The data was further analyzed separately in two subgroups; the photorefractive keratectomy /laser-assisted subepithelial keratomileusis (PRK/LASEK) group and the laser in situ keratomileusis (LASIK) group.

RESULTS: The overall post-operative IOP readings were significantly lower than pre-operative values. There was a significant difference in the lowering of the IOP readings between the two subgroups: LASIK caused a lower IOP reading than PRK/LASEK.

CONCLUSION: The change in corneal thickness and curvature affects the estimation of IOP with Goldmann applanation tonometry after excimer laser photorefractive surgery. The amount of reduction in IOP reading might be influenced by the specific laser surgical procedure. This is of clinical importance in the evaluation of any future glaucoma in the increasing number of patients who undergo photorefractive laser surgery.
Cornea. 2004 Apr;23(3):225-34.

Nordlund ML, Grimm S, Lane S,
Holland EJ.

Cincinnati Eye Institute and Department of Ophthalmology, University of Cincinnati College of Medicine, Cincinnati, OH 45242, USA. This email address is being protected from spambots. You need JavaScript enabled to view it.

PURPOSE: Interface inflammation is a common complication of laser in situ keratomileusis (LASIK). The most well-described presentation is diffuse lamellar keratitis (DLK), which typically develops early after LASIK and responds quickly to topical steroids. In this report, we describe a novel presentation of interface inflammation that resembles DLK in appearance but presents late in the postoperative period, is associated with increased intraocular pressure, and is exacerbated by steroid treatment.

METHODS: A retrospective case series and chart review of all patients treated in our tertiary care private practice for late-onset interface inflammation associated with elevated intraocular pressure.

RESULTS: Ten eyes in 6 patients with late-onset interface inflammation and increased intraocular pressure were identified. At presentation, all patients were presumed to have classic DLK and were treated initially with aggressive topical steroids. Eight of the 10 eyes were receiving topical steroids at the time of presentation. The average time of presentation was 17 days after LASIK (range, 7-34). Elevated intraocular pressure was noted on average 28 days after presentation (range, 8-69). Lamellar inflammation was exacerbated by topical steroids. Resolution of the interface inflammation did not occur until intraocular pressure was controlled.

CONCLUSIONS: This case series describes a clinically distinct form of interface inflammation that presents late and is associated with elevated intraocular pressure. The lamellar inflammation was refractory to topical steroids and only resolved when pressure was controlled. These findings suggest that elevated intraocular pressure can contribute to interface inflammation. Postoperative assessment of intraocular pressure is essential in patients presenting with flap inflammation.
Eye Contact Lens. 2006 Mar;32(2):88-93.  


Stapleton F, Hayward KB, Bachand N, Trong PH, Teh DW, Deng KM, Yang EI, Kelly SL, Lette M, Robinson D. 

From the Cornea and Contact Lens Research Unit (F.S., K.B.H., N.B., P.H.T., D.W.H.T., K.M.Y.D., E.I.H.Y.), School of Optometry and Vision Science and Vision Cooperative Research Centre, University of New South Wales, Sydney, Australia; and Sydney Laser and Vision Centre (S.L.K., M.L., D.R.), Bondi Junction, Australia.  

PURPOSE.: To evaluate the effect of laser in situ keratomileusis (LASIK) on corneal sensitivity, nerve morphology, and tear film characteristics.  

METHODS.: A cross-sectional study design was used. Eighteen patients (eight men and 10 women with a mean age of 36.9 +/- 11.2 years) who had undergone bilateral LASIK for low myopia within 18 months of the study and 28 control subjects (16 men and 12 women with a mean age of 27.2 +/- 7.7 years) were enrolled. Central and inferior corneal thresholds to mechanical (air) and chemical (air plus carbon dioxide) stimuli were determined by using a staircase technique. Stimuli of a 1-second duration at 34 degrees C were delivered with a CRCERT-Belmonte aesthesiometer. Images of subbasal nerves in the central cornea were captured with confocal microscopy. Nerve morphology was classified as no nerves, short nerves (<175 mum), or long nerves (>175 mum), with or without interconnections. Noninvasive tear break up time was measured. The phenol red thread test was used to indicate basal tear secretion. Differences between groups were evaluated with analysis of variance, and associations between variables were evaluated with parametric or nonparametric correlation, when appropriate.  

RESULTS.: Central corneal mechanical sensitivity was significantly reduced in the post-LASIK group compared with the control subjects (P<0.001). Nerve morphology was associated with mechanical threshold. Nerve morphology, mechanical sensitivity, and tear breakup time improved during the first 1 to 3 months after surgery, with little change thereafter. Chemical sensitivity was associated with tear secretion (P<0.05).  

CONCLUSIONS.: Central corneal mechanical sensitivity is reduced in patients after LASIK, with partial recovery seen 3 months after surgery. A similar recovery trend is seen for nerve morphology.

Journal of Refractive Surgery Vol. 22 No. 2 February 2006  

Manuel Ramírez, MD; Everardo Hernández-Quintela, MD, MSc; Valeria Sánchez-Huerta, MD; Ramón Naranjo-Tackman, MD  

PURPOSE: To describe the morphological characteristics of microfolds that appear at the corneal flap after LASIK, as seen under confocal microscopy.  

METHODS: Twenty-one eyes that had undergone LASIK were examined, all within 3 weeks to 1 month after surgery. A central scan of the total corneal thickness was obtained by using confocal microscopy in vivo. Confocal images were captured and digitized. The longitudinal orientation (vertical, horizontal, and oblique) and morphological characteristics of the microfolds were described and recorded.  

RESULTS: Six eyes had folds at the central corneal flap, visible as linear distortions in the confocal images: one fold had a vertical orientation, two were horizontal, and three were oblique. The folds were visible from the epithelial basal cell layer to the stromal portion of the flap and were deeper than Bowman’s layer.  

CONCLUSIONS: Confocal microscopy allowed visualization of microfolds after LASIK. With the appropriate software, it is possible to analyze the morphological characteristics of these folds. Flap microfolds after LASIK are deeper than Bowman’s layer.




Dr. Greg Gemoules, OD of Coppell, TX, an Optometrist who specializes in repairing the vision of patients damaged by refractive surgery by fitting them with hard contact lenses, claims that hard contact lenses, known as RGP’s or ‘rigid gas permeable’ lenses are the best option for those with laser-ruined eyesight. One reason he cites to promote RGP use for these visually compromised patients is a lack of availability of donor corneas due to the widespread practice of LASIK eye surgery.

Gemoules also claims that many corneal transplant recipients have worse vision than those with “LASIK difficulties”.

Gemoules stated:

“Many patients with corneal grafts have worse problems than patients with post-LASIK difficulties, and STILL require RGP contact lenses afterwards. Besides, the donor pool for donor corneas is being reduced by the number of patients who are getting LASIK.”


Here is an excerpt and link to a comment posted by Optometrist Dr. Greg Gemoules who specializes in the treatment of patients damaged by refractive surgery by fitting them with rigid gas permeable contact lenses.


Says Dr. Gemoules:


"Up to 40% of post-RK patients develop progressive hyperopia because of peripheral corneal ectasia due to the cornea being weakened by the incisions. Taking away tissue from the periphery, as is done with PRK or LASIK will not make the cornea any stronger."



DrG: The trend now is to ablate more tissue in the periphery in an attempt to reduce spherical aberration that is typically induced by refractive surgery and is responsible for a portion of the night vision disturbances and loss of visual quality experience by refractive surgery patients. We're just now seeing the long term effects of RK. One would expect that other corneal refractive surgical procedures, all of which compromise corneal strength and integrity, will have similar long term effects.

 Noncontact Tonometry in Patients After Myopic LASIK Surgery


J Cataract Refract Surg. 2004 May;30(5):1067-72.

Miyata K, Tokunaga T, Nakahara M, Ohtani S, Nejima R, Kiuchi T, Kaji Y, Oshika T.

Miyata Eye Hospital, Miyasaki, Japan.


PURPOSE: To prospectively assess the forward shift of the cornea after laser in situ keratomileusis (LASIK) in relation to the residual corneal bed thickness.


SETTING: Miyata Eye Hospital, Miyazaki, Japan.


METHODS: Laser in situ keratomileusis was performed in 164 eyes of 85 patients with a mean myopic refractive error of -5.6 diopters (D) +/- 2.8 (SD) (range -1.25 to -14.5 D). Corneal topography of the posterior corneal surface was obtained using a scanning-slit topography system before and 1 month after surgery. Similar measurements were performed in 20 eyes of 10 normal subjects at an interval of 1 month. The amount of anteroposterior movement of the posterior corneal surface was determined. Multiple regression analysis was used to assess the factors that affected the forward shift of the corneal back surface.


RESULTS: The mean residual corneal bed thickness after laser ablation was 388.0 +/- 35.9 microm (range 308 to 489 microm). After surgery, the posterior corneal surface showed a mean forward shift of 46.4 +/- 27.9 microm, which was significantly larger than the absolute difference of 2 measurements obtained in normal subjects, 2.6 +/- 5.7 microm (P<.0001, Student t test). Variables relevant to the forward shift of the corneal posterior surface were, in order of magnitude of influence, the amount of laser ablation (partial regression coefficient B = 0.736, P<.0001) and the preoperative corneal thickness (B = -0.198, P<.0001). The residual corneal bed thickness was not relevant to the forward shift of the cornea.

CONCLUSIONS: Even if a residual corneal bed of 300 microm or thicker is preserved, anterior bulging of the cornea after LASIK can occur. Eyes with thin corneas and high myopia requiring greater laser ablation are more predisposed to an anterior shift of the cornea.

 Undergoing Excimer Laser Refractive Surgery


Cornea. 23, 8 Supplement 1:S59-S64, November 2004.

Kamiya, Kazutaka MD *; Miyata, Kazunori MD +; Tokunaga, Tadatoshi COT +; Kiuchi, Takahiro MD ++; Hiraoka, Takahiro MD ++; Oshika, Tetsuro MD ++


Purpose: To review the time course of corneal anteroposterior shift and refractive stability after myopic excimer laser keratorefractive surgery.

Methods: We examined 65 eyes undergoing photorefractive keratectomy (PRK) and 45 eyes undergoing laser in situ keratomileusis (LASIK). Corneal elevation maps and pachymetry were obtained by scanning-slit corneal topography before; 1 week; and 1, 3, 6, and 12 months after surgery.

Results: Both PRK and LASIK induced significant forward shifts of the cornea. Corneal forward shift was progressive up to 6 months after PRK, but no progression was seen after LASIK. Progressive thinning and expansion of the cornea were not observed after either procedure. The amount of corneal forward shift showed a significant negative correlation with preoperative corneal thickness (r = -0.586; P < 0.01) and a significant positive correlation with the amount of myopic correction (r = 0.504; P < 0.01). A significant correlation was found between the amount of forward shift and the degree of myopic regression after surgery (r = -0.347; P < 0.05).

Conclusion: Myopic PRK and LASIK induce significant forward shifts of the cornea, which are not true corneal ectasia. Eyes with thinner corneas and higher myopia requiring greater ablation are more predisposed to anterior protrusion of the cornea. Corneal forward shift was progressive up to 6 months after PRK but not progressive after LASIK. Forward shift of the cornea can be one of the factors responsible for myopic regression after surgery.

2005 Jan;24(1):92-102.

Pathologic findings in postmortem corneas after successful laser in situ keratomileusis.

Kramer TR, Chuckpaiwong V, Dawson DG, L'Hernault N, Grossniklaus HE, Edelhauser HF.

Emory Eye Center, Emory University, Atlanta, GA 30322, USA. 




PURPOSE: To examine the histologic and ultrastructural features of human corneas after successful laser in situ keratomileusis (LASIK).


METHODS: Corneas from 48 eyes of 25 postmortem patients were processed for histology and transmission electron microscopy (TEM). The 25 patients had LASIK between 3 months and 7 years prior to death. Evaluation of all 5 layers of the cornea and the LASIK flap interface region was done using routine histology, periodic acid-Schiff (PAS)-stained specimens, toluidine blue-stained thick sections, and TEM.


RESULTS: In patients for whom visual acuity was known, the first postoperative day uncorrected visual acuity was 20/15 to 20/30. In patients for whom clinical records were available, the postoperative corneal topography was normal and clinical examination showed a semicircular ring of haze at the wound margin of the LASIK flap. Histologically, the LASIK flap measured, on average, 142.7 microm (range, 100-200). A spectrum of abnormal histopathologic and ultrastructural findings was present in all corneas. Findings at the flap surface included elongated basal epithelial cells, epithelial hyperplasia, thickening and undulations of the epithelial basement membrane (EBM), and undulations of Bowman's layer. Findings in or adjacent to the wound included collagen lamellar disarray; activated keratocytes; quiescent keratocytes with small vacuoles; epithelial ingrowth; eosinophilic deposits; PAS-positive, electron-dense granular material interspersed with randomly ordered collagen fibrils; increased spacing between collagen fibrils; and widely spaced banded collagen. There was no observable correlation between postoperative intervals and the severity or type of pathologic change except for the accumulation the electron-dense granular material.


CONCLUSIONS: Permanent pathologic changes were present in all post-LASIK corneas. These changes were most prevalent in the lamellar interface wound. These changes along with other pathologic alterations in post-LASIK corneas may change the functionality of the cornea after LASIK.


Invest Ophthalmol Vis Sci. 2004 Nov;45(11):3991-6.

Corneal reinnervation after LASIK: prospective 3-year longitudinal study.

Calvillo MP, McLaren JW, Hodge DO, Bourne WM.

Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.




PURPOSE: To measure the return of innervation to the cornea during 3 years after LASIK.

METHODS: Seventeen corneas of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D were examined by confocal microscopy before surgery, and at 1, 3, 6, 12, 24, and 36 months after surgery. In all available scans, the number of nerve fiber bundles and their density (visible length of nerve per frame area), orientation (mean angle), and depth in the cornea were measured.

RESULTS: The number and density of subbasal nerves decreased >90% in the first month after LASIK. By 6 months these nerves began to recover, and by 2 years they reached densities not significantly different from those before LASIK. Between 2 and 3 years they decreased again, so that at 3 years the numbers remained <60% of the pre-LASIK numbers (P <0.001). In the stromal flap most nerve fiber bundles were also lost after LASIK, and these began recovering by the third month, but by the third year they did not reach their original numbers (P <0.001). In the stromal bed (posterior to the LASIK flap interface), there were no significant changes in nerve number or density. As the subbasal nerves returned, their mean orientation did not change from the predominantly vertical orientation before LASIK. Nerve orientation in the stromal flap and the stromal bed also did not change.

CONCLUSIONS: Both subbasal and stromal corneal nerves in LASIK flaps recover slowly and do not return to preoperative densities by 3 years after LASIK. The numbers of subbasal nerves appear to decrease between 2 and 3 years after LASIK. The orientation of the regenerated subbasal nerves remains predominantly vertical.


Journal of Refractive Surgery Vol. 21 No. 2 March/April 2005

"In particular, a forward shift and an increase in power of the posterior surface was predicted for myopic LASIK, in agreement with previous experimental findings."     


Ophthalmologe. 1995 Aug;92(4):389-96.


OBJECTIVE: To analyze critically refractive surgery of the cornea by excimer laser and to compare laser surgery with other methods of treatment of refractive errors of the eye.

MATERIAL AND METHODS: This analysis has to be restricted to a comparison of the treatment of myopia by keratotomy and photoablation with the ArF excimer laser. Correction of hypermetropia and of astigmatismus has to be left out, along with all the other methods to correct myopia, such as glasses, contact lenses, keratomileusis, epikeratoplasty, alloplastic implants, implantation of intraocular lenses with negative power, and replacement of the clear lens by an posterior chamber lens. The essential literature is screened. For intrastromal ablation with the picosecond Nd:YLF laser we relay on own experiences, also with the use of the ArF excimer laser we are not without own experiences.

RESULTS AND STATEMENTS: For comparison of refractive surgery of the cornea not only the PERK study and the recommendations of the American Academy of Ophthalmology have to be considered, but also the newest developments in radial keratotomy such as two-step incision and reoperation with reopening of the keratotomy wounds. With these techniques the same precision can be reached as with the excimerlaser, and also higher myopias can be corrected. The dangers of the procedure, such as infection, perforation at surgery or laceration by contusion remain much larger. Intrastromal photoablation did not reach clinical maturity. Superficial photoablation is an almost safe procedure. A reduction of 3 D of myopia can be reached with satisfying precision, although higher myopias are still a problem. Pain following the ablation is considerable. Haze and disturbed vision at night can be present; infectious keratitis is rare, but possible.

CONCLUSIONS: The critical fact of both procedures, keratotomy and photoablation with excimer laser, remains that healthy eyes are treated; therefore, even rare complications weigh much heavier than if sick eyes are treated. Because this is cosmetic surgery, the individuum asking for this type of procedure has to pay for on his own. Olson demands: "In determining when new technology is acceptable, we must consider the financial cost and the expected benefit to society. Is it an equitable tradeoff?" If we look at refractive surgery, especially laser photoablation, in the context of the needs for ophthalmic care of the whole world, then this type of surgery is out of proportion. The balance could be restored if, with every laser application, funds were given for third-world projects. Excimer-laser surgery may be justified insofar as the research with these lasers leads to useful therapeutic methods.

 and clinical correlations


Schmack I, Dawson DG, McCarey BE, Waring GO 3rd, Grossniklaus HE, Edelhauser HF.

Emory Eye Center, Emory University School of Medicine, Atlanta, GA 30322, USA.



PURPOSE: To measure the cohesive tensile strength of human LASIK corneal wounds.

METHODS: Twenty-five human eye bank corneas from 13 donors that had LASIK were cut into 4-mm corneoscleral strips and dissected to expose the interface wound. Using a motorized pulling device, the force required to separate the wound was recorded. Intact and separated specimens were processed for light and electron microscopy. Five normal human eye bank corneas from 5 donors served as controls. A retrospective clinical study was done on 144 eyes that had LASIK flap-lift retreatments, providing clinical correlation.

RESULTS: The mean tensile strength of the central and paracentral LASIK wounds showed minimal change in strength over time after surgery, averaging 2.4% (0.72 +/- 0.33 g/mm) of controls (30.06 +/- 2.93 g/mm). In contrast, the mean peak tensile strength of the flap wound margin gradually increased over time after surgery, reaching maximum values by 3.5 years when the average was 28.1% (8.46 +/- 4.56 g/mm) of controls. Histologic and ultrastructural correlative studies found that the plane of separation always occurred in the lamellar wound, which consisted of a hypocellular primitive stromal scar centrally and paracentrally and a hypercellular fibrotic stromal scar at the flap wound margin. The pathologic correlations demonstrated that the strongest wound margin scars had no epithelial cell ingrowth-the strongest typically being wider or more peripherally located. In contrast, the weakest wound margin scars had epithelial cell ingrowth. The clinical series demonstrated the ability to lift LASIK flaps without complications during retreatments up to 8.4 years after initial surgery, correlating well with the laboratory results.

CONCLUSIONS: The human comeal stroma typically heals after LASIK in a limited and incomplete fashion; this results in a weak, central and paracentral hypocellular primitive stromal scar that averages 2.4% as strong as normal comeal stroma. Conversely, the LASIK flap wound margin heals by producing a 10-fold stronger, peripheral hypercellular fibrotic stromal scar that averages 28.1% as strong as normal comeal stromal, but displays marked variability.

Cornea. 2005 Jan;24(1):92-102. Related Articles, Links

Pathologic findings in postmortem corneas after successful laser in situ keratomileusis.

Kramer TR, Chuckpaiwong V, Dawson DG, L'Hernault N, Grossniklaus HE, Edelhauser HF.

Emory Eye Center, Emory University, Atlanta, GA 30322, USA.


PURPOSE: To examine the histologic and ultrastructural features of human corneas after successful laser in situ keratomileusis (LASIK).

METHODS: Corneas from 48 eyes of 25 postmortem patients were processed for histology and transmission electron microscopy (TEM). The 25 patients had LASIK between 3 months and 7 years prior to death. Evaluation of all 5 layers of the cornea and the LASIK flap interface region was done using routine histology, periodic acid-Schiff (PAS)-stained specimens, toluidine blue-stained thick sections, and TEM.

RESULTS: In patients for whom visual acuity was known, the first postoperative day uncorrected visual acuity was 20/15 to 20/30. In patients for whom clinical records were available, the postoperative corneal topography was normal and clinical examination showed a semicircular ring of haze at the wound margin of the LASIK flap. Histologically, the LASIK flap measured, on average, 142.7 microm (range, 100-200). A spectrum of abnormal histopathologic and ultrastructural findings was present in all corneas. Findings at the flap surface included elongated basal epithelial cells, epithelial hyperplasia, thickening and undulations of the epithelial basement membrane (EBM), and undulations of Bowman's layer. Findings in or adjacent to the wound included collagen lamellar disarray; activated keratocytes; quiescent keratocytes with small vacuoles; epithelial ingrowth; eosinophilic deposits; PAS-positive, electron-dense granular material interspersed with randomly ordered collagen fibrils; increased spacing between collagen fibrils; and widely spaced banded collagen. There was no observable correlation between postoperative intervals and the severity or type of pathologic change except for the accumulation the electron-dense granular material.

CONCLUSIONS: Permanent pathologic changes were present in all post-LASIK corneas. These changes were most prevalent in the lamellar interface wound. These changes along with other pathologic alterations in post-LASIK corneas may change the functionality of the cornea after LASIK.

To understand the extent of the damage, you really should get the full-text of this article.

1: Ophthalmology. 2005 Apr;112(4):634-44.

Dawson DG, Holley GP, Geroski DH, Waring GO 3rd, Grossniklaus HE, Edelhauser HF.

Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, USA.


OBJECTIVE: To perform confocal microscopy on postmortem human LASIK corneas and correlate these findings to histologic and ultrastructure evaluations.

DESIGN: Prospective, consecutive, observational case series.

PARTICIPANTS: Ninety postmortem LASIK corneas (47 patients) were evaluated for histopathology, of which 22 consecutive corneas (12 patients) were also evaluated by confocal microscopy. Six normal corneas (3 patients) served as controls.

METHODS: This observational case series involving 22 corneas from 12 patients with postoperative intervals from 1 month to 6.5 years after LASIK surgery were collected. The corneas were mounted in an artificial anterior chamber and perfused with balanced salt solution before confocal microscopy was performed on the center of the cornea. The corneas were then bisected and processed for light and transmission electron microscopy.

RESULTS: Confocal microscopy, along with histologic and ultrastructural correlations, demonstrated that the most prevalent alterations in the centers of LASIK corneas were a slightly thickened epithelium caused by focal basal epithelial cell hypertrophic modifications, random undulations in Bowman's layer over the flap surface, and a variably thick hypocellular primitive stromal interface scar. By using confocal microscopy, the interface wound was easily identified in 100% of the cases because numerous brightly reflective interface particles were always present in the hypocellular primitive stromal scar. These particles were found primarily to consist of organic cellular constituents, some of which were transient in nature.

CONCLUSION: After LASIK, active stromal wound healing in the central cornea results in the production of a hypocellular primitive stromal scar, whereas secondary tissue adjustments seem to cause the Bowman's layer undulations and the subsequent epithelial cell modifications. Most of the interface particles revealed by confocal microscopy in the region of the stromal scar are organic in nature and presumably innocuous to the cornea.

Invest Ophthalmol Vis Sci. 2004 Nov;45(11):3991-6.

Calvillo MP, McLaren JW, Hodge DO, Bourne WM.

Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.


PURPOSE: To measure the return of innervation to the cornea during 3 years after LASIK.

METHODS: Seventeen corneas of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D were examined by confocal microscopy before surgery, and at 1, 3, 6, 12, 24, and 36 months after surgery. In all available scans, the number of nerve fiber bundles and their density (visible length of nerve per frame area), orientation (mean angle), and depth in the cornea were measured.

RESULTS: The number and density of subbasal nerves decreased >90% in the first month after LASIK. By 6 months these nerves began to recover, and by 2 years they reached densities not significantly different from those before LASIK. Between 2 and 3 years they decreased again, so that at 3 years the numbers remained <60% of the pre-LASIK numbers (P <0.001). In the stromal flap most nerve fiber bundles were also lost after LASIK, and these began recovering by the third month, but by the third year they did not reach their original numbers (P <0.001). In the stromal bed (posterior to the LASIK flap interface), there were no significant changes in nerve number or density. As the subbasal nerves returned, their mean orientation did not change from the predominantly vertical orientation before LASIK. Nerve orientation in the stromal flap and the stromal bed also did not change.

CONCLUSIONS: Both subbasal and stromal corneal nerves in LASIK flaps recover slowly and do not return to preoperative densities by 3 years after LASIK. The numbers of subbasal nerves appear to decrease between 2 and 3 years after LASIK. The orientation of the regenerated subbasal nerves remains predominantly vertical.

Ophthalmology. 2002 Apr;109(4):659-65.  

Hamilton DR, Manche EE, Rich LF, Maloney RK.  Jules Stein Eye Institute, University of California-Los Angeles, Los Angeles, CA 90095, USA.  

PURPOSE: To report the ocular manifestations and clinical course of eyes developing interface fluid after laser in situ keratomileusis (LASIK) surgery from a steroid-induced rise in intraocular pressure.  

DESIGN: Retrospective, noncomparative interventional case series.  

PARTICIPANTS/INTERVENTION: We examined six eyes of four patients who had diffuse lamellar keratitis develop after uneventful myopic LASIK surgery and were treated with topical corticosteroids.  

PRINCIPAL OUTCOME MEASURE: Slit-lamp findings, intraocular pressure measurements, and visual field loss.

RESULTS: All eyes had a pocket of fluid develop in the lamellar interface between the flap and the stromal bed associated with a corticosteroid-induced rise in intraocular pressure. However, because of the interface fluid, intraocular pressure was normal or low by central corneal Goldmann applanation tonometry in all eyes. The elevated intraocular pressure was diagnosed by peripheral measurement in several cases after months of elevated pressure. All six eyes had visual field defects develop. Three eyes of two patients had severe glaucomatous optic neuropathy and decreased visual acuity develop as a result of undiagnosed steroid-induced elevated intraocular pressure.  

CONCLUSIONS: A steroid-induced rise in intraocular pressure after LASIK can cause transudation of aqueous fluid across the endothelium that collects in the flap interface. The interface fluid leads to inaccurately low central applanation tonometry measurements that obscure the diagnosis of steroid-induced glaucoma. Serious visual loss may result.

J Cataract Refract Surg. 2002 Feb;28(2):356-9.  

Shaikh NM, Shaikh S, Singh K, Manche E.  Department of Ophthalmology, Stanford University School of Medicine, Stanford, California 94305, USA 

We describe 2 patients, one a glaucoma suspect because of family history and the other with juvenile glaucoma. Both patients developed complications after laser in situ keratomileusis that required frequent topical steroids, leading to steroid-induced glaucoma. In both cases, corneal edema from the acute rise in intraocular pressure (IOP) caused inaccurate IOP measurement by standard methods. The inability to recognize glaucoma early may have resulted in significant irreversible vision loss.

Ophthalmology. 2005 Jul;112(7):1207-12.   

Arevalo JF, Mendoza AJ, Velez-Vazquez W, Rodriguez FJ, Rodriguez A, Rosales-Meneses JL, Yepez JB, Ramirez E, Dessouki A, Chan CK, Mittra RA, Ramsay RC, Garcia RA, Ruiz-Moreno JM.  Retina and Vitreous Service, Clinica Oftalmologica Centro Caracas, Caracas, Venezuela. This email address is being protected from spambots. You need JavaScript enabled to view it.  

PURPOSE: To describe 19 patients (20 eyes) who developed a macular hole (MH) after undergoing bilateral LASIK for the correction of myopia.  

DESIGN: Noncomparative, interventional, retrospective, multicenter case series.  

PARTICIPANTS: Nineteen patients (20 eyes) who developed an MH after bilateral LASIK for the correction of myopia at 10 institutions in Venezuela, Colombia, Puerto Rico, Spain, and the United States.  

METHODS: Chart review.  

MAIN OUTCOME MEASURE: Macular hole development.  

RESULTS: The MH formed between 1 to 83 months after LASIK (mean, 12.1). In 60% of cases, the MH developed < or =6 months after LASIK, and in 30% of cases it developed > or =1 year after LASIK. Eighteen of 19 (94.7%) patients were female. Mean age was 46 years (range, 25-65). All eyes were myopic (range, -0.50 to -19.75 diopters [mean, -8.9]). Posterior vitreous detachment was not present before and was documented after LASIK in 55% of eyes. A vitrectomy closed the MH on the 14 eyes that underwent surgical management, with an improvement of final best-corrected visual acuity in 13 of 14 (92.8%) patients. Our 20 eyes with a full-thickness MH after LASIK reflect an incidence of approximately 0.02% (20/83938).  

CONCLUSION: An MH may infrequently develop after LASIK for the correction of myopia. Our study shows that vitreoretinal surgery can be successful in restoring vision for most myopic eyes with an MH after LASIK. Vitreoretinal interface changes may play a role in MH formation after LASIK for the correction of myopia.

Ophthalmologe. 2006 Feb 8; [Epub ahead of print]

[Article in German]

Knorz MC.

FreeVis LASIK Zentrum, Universitatsklinikum Mannheim, .

In surface ablation, haze is the most frequent complication.After LASIK, microkeratome-related complications are rare today and usually resolve without sequelae, provided no ablation was done. Postoperative flap complications such as flap slippage usually occur during the first few days after surgery and should be treated as early whenever present.Interface complications are a new diagnostic entity as the interface between flap and stroma presents a space where fluid or cells can accumulate. Diffuse lamellar keratitis usually occurs within the first few postoperative days and should be treated aggressively to avoid scarring. Epithelial ingrowth is another rare complication usually requiring treatment. Corneal hydrops with fluid accumulation in the interface is a very rare but important phenomenon related to steroid-induced glaucoma but presenting with false low tonometry readings.Corneal ectasia is extremely rare and in most cases related to thin stromal beds. However, its pathogenesis is not yet completely understood, and it may occur in "normal" eyes, too. Dry eye syndrome is the most frequent complication after LASIK. It is usually benign but may cause significant visual impairment in rare cases.

Lamellar keratitis following LASIK


Ophthalmol Clin North Am. 2002 Mar;15(1):35-40.  

Chao CW, Azar DT.  Division of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA.  

Distinguishing between an infectious or sterile lamellar keratitis is the most important first step in evaluating patients with interface infiltrates after LASIK. The mechanisms by which infectious keratitis develops are more straightforward than for DLK and deal with the introduction of microbial pathogens into the lamellar flap during LASIK. Prevention emphasizes reducing contamination risks and treating any pre-existing ocular infections. The mechanisms of the development of DLK are likely multifactorial, and factors such as microkeratome debris, eyelid secretions, other debris, epithelial defects, and bacterial endotoxin have been suggested. Overall, much remains to be elucidated in order to devise effective prevention measures.

Several more studies related to Diffuse Lamellar Keratitis submitted, with commentary (italics) from an avid reader:


Ophthalmology. 1998 Sep;105(9):1721-6.  

Diffuse lamellar keratitis. A new syndrome in lamellar refractive surgery.  

Smith RJ, Maloney RK.  Jules Stein Eye Institute, UCLA School of Medicine, USA.  

OBJECTIVE: This study aimed to describe a syndrome that the authors call diffuse lamellar keratitis that follows laser in situ keratomileusis (LASIK) and related lamellar corneal surgery.

DESIGN: Noncomparative case series and record review.  

PARTICIPANTS: Thirteen eyes of 12 patients in whom infiltrates developed in the interface after lamellar refractive surgery were studied.  

INTERVENTION: Topical antibiotics or corticosteroids or both were administered.  

MAIN OUTCOME MEASURES: Corneal infiltrate appearance, focality, location, and clinical course were measured.  

RESULTS: Patients presented between 2 and 6 days after surgery with pain, photophobia, redness, or tearing. Ten cases directly followed either myopic keratomileusis or LASIK. Three cases followed enhancement surgery without the use of a microkeratome. All 13 cases had infiltrates that were diffuse, multifocal, and confined to the flap interface with no posterior or anterior extension. The overlying epithelium was intact in each case. Cultures were negative in the two cases cultured. Ten eyes were treated with antibacterial agents; two eyes had fluorometholone four times daily added to the routine postoperative antibacterial regimen, and one eye had the antibacterial agent discontinued and was treated with topical fluorometholone alone. All infiltrates resolved without sequelae.  

CONCLUSIONS: A distinct syndrome of unknown cause of noninfectious diffuse infiltrates in the lamellar interface is described. It can be distinguished from infectious infiltrates by clinical presentation and close follow-up. Patients with the syndrome should be spared the more invasive treatment of infectious keratitis.  

DLK was unheard of before LASIK, yet since LASIK there have been thousands of cases, numerous reports in the medical literature as well as a hot topic in the industry tabloids.  

One of the first things that came to mind was the article that appeared in the JRS in 2002 titled "A Mysterious Tale: A Search for the Cause of 100+ Cases of Diffuse Lamellar Keratitis". It was submitted for publication anonymously. Surgeon X had a DLK rate at one point as high as 50%. For those who are unfamiliar with DLK, it can cause permanent vision loss from scarring, or even loss of the cornea entirely. I found it unbelievable that this surgeon continued performing LASIK while he "searched for the cause". Do you think he informed his patients that his rate of DLK was 50%? Sounds like he used his patients as human guinea pigs.


LASIK is an elective surgery performed on a vital sensory organ. I see people comparing it to other elective surgeries. It is your eyes, your vision, your primary interface with the world! Come on, that's not the same as other elective surgeries. This kind of elective surgery should be held to much, much higher standards because vision is so precious and so important to a person's overall well-being and quality of life. A person presenting for LASIK is not sick, does not have a disease, and lives a perfectly normal life with great correctable vision.  I have such a hard time understanding how "doctors" can promote a surgery that triggers so many adverse, life-altering "side effects" in a normal healthy human being.  

DLK is not the only new syndrome induced by LASIK.  "Neurotrophic keratopathy" and "neurotrophic epitheliopathy" are terms used to describe LASIK induced dry eye which results from the severing of the corneal nerves by the microkeratome. Doctors routinely tell their patients that dry eyes is a temporary condition and advise the use of artificial tears for a period of weeks. The brochure given out by my LASIK surgeon said that eye drops are only needed for 2 weeks. Excuse me, it's over 5 years later, and I still use eye drops daily due to horrible dry eye with associated pain and burning.

One peer-reviewed article showed that at 3 years post-op the corneal nerves were still less than 60% of pre-op densities. No article has ever shown that the nerves fully recover to their normal patterns. Yet surgeons don't inform patients that their corneal nerves will be permanently damaged.  There's another new syndrome of the Intralase flap. Patients were coming back in the early post-op period with such extreme light sensitivity that they had to wear dark sunglasses indoors. Surgeons were so puzzled by this that it left them scratching their heads.

Finally one surgeon coined the term "Transient Light Sensitivity", or TLS for short, and it made them all very happy that now there was a term for it. Now, instead of looking like a moron to their patients because they didn't have a diagnosis, they could say "Oh, you have TLS", give them some steroids and a pat on the head and send them on their way. (be sure to warn your patients of the dangers of prolonged steriod use and monitor their IOP closely!)

This article shows that patients who think they are out of the woods because one day or one week post-op they have 20/20 acuity and no complications could be in for an unpleasant late surprise. 

  Reports: Diffuse Lamellar Keratitis 6 Months After Uneventful Laser in situ Keratomileusis  

Journal of Refractive Surgery Vol. 19 No. 1 January/February 2003


José I. Belda, MD, PhD; Alberto Artola, MD, PhD; Jorge Alió, MD, PhD  

PURPOSE Diffuse lamellar keratitis after laser in situ keratomileusis (LASIK) typically occurs between 1 and 7 days after the procedure, and its etiologic factor(s) remain unknown.  

METHODS We describe a case of diffuse lamellar keratitis 6 months after uneventful LASIK in a 25-year-old woman.  

RESULTS Slit-lamp microscopy showed a diffuse infiltrate confined to the interface, extending to the visual axis, with no other relevant findings. Late on-set diffuse lamellar keratitis was our provisional diagnosis and treatment with topical corticosteroids was instituted, with rapid response and improvement of the clinical signs and symptoms.  

CONCLUSIONS This case supports the theory that a previously inert inciting agent could cause a delayed toxic or inflammatory response of the cornea several months after surgery.

[J Refract Surg 2003;19:70-71]  From the full text: "Possible etiologies include metallic debris from the microkeratome or blade, bacterial endotoxins, meibomian gland oils, debris from corneal ablation or from absorbent sponges, povidone-iodine solutions, and surgical glove talc."

Diffuse lamellar keratitis complicating laser in situ keratomileusis Post-marketing surveillance of an emerging disease in British Columbia, Canada, 2000-2002.


J Cataract Refract Surg. 2005 Dec;31(12):2340-2344  

Bigham M, Enns CL, Holland SP, Buxton J, Patrick D, Marion S, Morck DW, Kurucz M, Yuen V, Lafaille V, Shaw J, Mathias R, Vanandel M, Peck S.  

PURPOSE: To describe a surveillance system and summarize data between January 2000 and December 2002 regarding diffuse lamellar keratitis (DLK), a complication of laser in situ keratomileusis (LASIK) surgery.  

SETTING: Community-based clinics in British Columbia, Canada, in which LASIK surgery is performed.  

METHODS: Monthly, all clinics in which LASIK is performed reported the number of LASIK procedures and nonnominal cases of DLK (by grade and onset date) to the British Columbia Centre for Disease Control. Diffuse lamellar keratitis outbreaks were investigated, and prevention and control measures were recommended.  

RESULTS: From 2000 to 2002, approximately 72 000 LASIK procedures were performed, with a mean DLK incidence rate of 0.67% (95% confidence interval, 0.61-0.73). The overall proportion of DLK cases attributed to outbreaks was 64%, decreasing from 72% in 2000 to 40% in 2003.  

CONCLUSIONS: An effective DLK surveillance program was implemented at all laser refractive clinics in British Columbia. Reported DLK incidence was 0.67 cases per 100 procedures, with 64% occurring in outbreaks.

Journal of Refractive Surgery Vol. 22 No. 2 February 2006  

Ching-Liang Kuo, MD; Hsiu-Fen Lin, MD; Po-Chiung Fang, MD; Hsi-Kung Kuo, MD; David Hui-Kang Ma, MD, PhD  

PURPOSE: To report a case of late onset lamellar keratitis and epithelial ingrowth associated with orbital cellulitis 1 month after LASIK surgery.  

METHODS: A 19-year-old patient presented with pain and subsequent blurry vision in the right eye. One month prior to presentation, he had undergone LASIK in both eyes. Orbital cellulitis was suspected.  

RESULTS: Under aggressive treatment, the patient recovered from orbital cellulitis and lamellar keratitis and he also regained his vision with topical steroid treatment.  

CONCLUSIONS: Lamellar keratitis does not always occur early following LASIK and may be associated with orbital cellulitis.  

[J Refract Surg. 2006;22:202-204.]  

Here is a link to a description of orbital cellulitis:  

Cataract & Refractive Surgery Today May, 2003  

Spherical Aberration and Its Symptoms  Theories on why it occurs and how new technology may address the problem.  



SYMPTOMS CORRELATED WITH SPHERICAL ABERRATIONS: Standard laser refractive surgery performed on patients with large scotopic pupil sizes is associated with nighttime vision problems such as halos.12 The increased amount of higher-order aberrations after standard LASIK is consistent with the relatively common patient comment, “I can read 20/20, but my vision is not as good as it was before.”13   We analyzed 105 eyes that underwent LASIK correction and correlated their symptoms with higher-order aberrations. Our analysis of optical symptoms and measured aberrations for a scotopic pupil size showed a statistically significant correlation between higher-order aberrations and glare (P=.041) as well as starburst (P=.004). When we broke down these aberrations into individual Zernike components, spherical aberration was the predominant cause, with a statistically significant correlation to glare (P=.010) and starburst (P=.014). Halos seemed to be associated with spherical aberration for the scotopic pupil size (P=.053). Table 1 shows the relationship of spherical aberration and coma with patients’ symptoms.  

SPHERICAL ABERRATION PREVENTION AND CORRECTION: Surgeons must exercise care when treating eyes with larger scotopic pupils, especially if the procedure is expected to induce higher levels of spherical aberration (patients with large pupils will experience more symptoms with higher levels of spherical aberration). Customized laser ablations attempt to minimize these symptoms by more effectively avoiding laser-induced spherical aberrations. The ideal ablation profile for correcting refractive error without generating spherical aberration is to reshape the cornea with a lesser radius of curvature in the midperiphery rather than in the center. This difference in asphericity corrects the spherical aberration of the eye, because the flatter surface will cause less refraction of the peripheral rays.14

JRS September/October 2005 21:5 p502.
Lin and Tsai.
Retinal Plebitis After LASIK



"An IOP of at least 65mmHg is necessary to create a corneal flap with the microkeratome. During this time, the shape of the anterior segment may change rapidly and structures posterior to the suction ring are also compressed in sequence. When the suction stops and the suction ring is released, ocular decompression leads to dynamic equatorial elongation and anterior-posterior contraction. This barotrauma is analagous to what happens in closed eye injury, and can alter delicate retinal structures, especially small vessels, and induce vitreoretinal traction at the vitreous base and posterior pole. Sudden elevation of IOP also disturbs the retinal circulation and increases venous pressure, which results in retinal ischemia. All of these conditions may aggravate the original impaired blood-retinal barrier in highly myopic eyes and increase vascular permeability, leading to the loss of integrity of tight junctions of endothelial cells. Laser in-situ keratomilieusis-induced shock waves can generate up to 100atm. Although the pressure decreases steadily to values below 10 bars toward the retina, we believe it may still cause mechanical stress to the retina, resulting in structural damage and intraocular inflammation.

In addition, total energy and duration increase with higher refractive error and the effect of mechanical stress may be more severe in higher myopia, which has more liquification of the posterior vitreous gel."

PURPOSE: To evaluate components of the integrated ocular surface/lacrimal gland unit in a series of patients before and after undergoing bilateral laser in situ keratomileusis (LASIK).


DESIGN: Prospective, noncomparative case series.


PARTICIPANTS: Forty-eight eyes of 14 men and 34 women (age range, 26-54; mean, 39.2 years) who underwent bilateral LASIK for myopia or myopic astigmatism.

METHODS: LASIK was performed using a VISX Star Excimer Laser (Santa Clara, CA). Patients completed a questionnaire containing 11 questions that evaluated the character and severity of ocular irritation symptoms. Snellen visual acuity, tear fluorescein clearance, corneal fluorescein staining, aqueous tear production by the Schirmer 1 test, and corneal and conjunctival sensitivity were measured in each eye. Corneal surface regularity (SRI) was evaluated with the Tomey TMS-1 (Tomey, Cambridge, MA) topography instrument. Each randomly chosen eye was evaluated 1 to 2 days (T0) before LASIK and 7 days (T1), 1 (T2), 2 (T3), 6 (T4), 12 (T5), and 16 (T6) months postoperatively. A Wilcoxon test, two-tailed paired t test, Friedman test, or analysis of variance were used for statistical comparisons.


MAIN OUTCOME MEASURES: Components of the integrated ocular surface/lacrimal gland unit.


RESULTS: Both corneal and conjunctival sensitivity were noted to be significantly decreased from preoperative levels at 1week, 1 month, 12 months, and 16 months postoperatively (P < 0.0002 at each time point). Symptom severity scores were significantly increased at 1 week, 12 months, and 16 months postoperatively (P < 0.007 at all time points). The mean Schirmer 1 test scores were 24 +/- 14 mm preoperatively, and they decreased to 18 +/- 14 mm by 1 month postoperatively (P < 0.001). Tear fluorescein clearance showed a linear increase postoperatively and was significantly greater than baseline (P < 0.001) at each time point. There was a significant increase in punctate corneal fluorescein staining at 1 week postoperatively (P < 0.0001), but staining returned to baseline by 12 months. There was a statistically significant increase in SRI 1 week postoperatively (P < 0.007) with return to baseline levels by 6 months.

CONCLUSIONS: Sensory denervation of the ocular surface after bilateral LASIK disrupts ocular surface tear dynamics and causes irritation symptoms. Patients undergoing LASIK should be informed of these risks.

 - Corneal sensation remained reduced 16 months after LASIK

 - Conjunctival sensation remained reduced 16 months after LASIK

 - Tear clearance remained reduced 16 months after LASIK.

J Biomech Eng. 2006 Feb;128(1):150-60.   

Alastrue V, Calvo B, Pena E, Doblare M.  Group of Structural Mechanics and Material Modelling, Aragon Institute of Engineering Research (13A), University of Zaragoza, Spain 

The aim of refractive corneal surgery is to modify the curvature of the cornea to improve its dioptric properties. With that goal, the surgeon has to define the appropriate values of the surgical parameters in order to get the best clinical results, i.e., laser and geometric parameters such as depth and location of the incision, for each specific patient. A biomechanical study before surgery is therefore very convenient to assess quantitatively the effect of each parameter on the optical outcome. A mechanical model of the human cornea is here proposed and implemented under a finite element context to simulate the effects of some usual surgical procedures, such as photorefractive keratectomy (PRK), and limbal relaxing incisions (LRI). This model considers a nonlinear anisotropic hyperelastic behavior of the cornea that strongly depends on the physiological collagen fibril distribution. We evaluate the effect of the incision variables on the change of curvature of the cornea to correct myopia and astigmatism. The obtained results provided reasonable and useful information in the procedures analyzed. We can conclude from those results that this model reasonably approximates the corneal response to increasing pressure. We also show that tonometry measures of the IOP underpredicts its actual value after PRK or LASIK surgery.

J Cataract Refract Surg. 2005 Nov;31(11):2216-20.


Hamill MB, Quayle WH.

From the Cullen Eye Institute, Baylor College of Medicine, Department of Ophthalmology (Hamill), and UTMB Galveston Houston Eye Associates (Quayle), Houston, Texas, USA.


This report illustrates the surgical approach to and results of a complex iris reconstruction. The presentation and long-term visual and architectural results (follow-up of 4 years) of the repair of a severe anterior segment injury after entry into the anterior chamber by a microkeratome during laser in situ keratomileusis is described. The techniques used in the repair are described in detail, and a historical review of iris repair techniques is presented.


Article is only available if purchased. The fact this did happen due to LASIK, the industry will still deny it a risk. 

Central Corneal Thickness, and Posterior Elevation




Optometry & Vision Science. 82(5):428-431, May 2005.


Purpose. The purpose of this study was to assess interocular corneal symmetry in average simulated keratometry, corneal thickness, and posterior corneal elevation.

Methods. This retrospective analysis included data from scanning slit topography (Orbscan II; Bausch and Lomb, Rochester, NY) on 242 eyes from 121 consecutive patients undergoing standard evaluation for consideration of elective laser vision correction. The symmetry between the right and left eye in average simulated keratometry, minimum central corneal thickness, and posterior corneal elevation was assessed by comparative data analysis.

Results. Simulated keratometry ranged from 39.9 to 48.6 D. The interocular difference in average simulated keratometry was 0.47 D (standard deviation [SD] 0.43). The interocular Pearson correlation coefficient for average simulated keratometry was 0.90 (p < 0.001). The range of minimum corneal thickness was 432 to 628 [mu]m. The interocular Pearson correlation coefficient for minimum central corneal thickness was 0.95 (p < 0.001). Right and left eye minimum corneal thickness differed by an average 8 [mu]m (SD 7). The range of posterior elevation was -4 to 54 [mu]m. The average difference in posterior corneal elevation between the right and left eye was 6 [mu]m (SD 5). The interocular Pearson correlation coefficient for posterior corneal elevation was 0.72 (p < 0.001). The average posterior elevation was 19 [mu]m (SD 11).

Conclusions. Although a wide range of values exists in simulated keratometry, minimum corneal thickness, and posterior corneal elevation, interocular symmetry in all these parameters was very high in this group of consecutive patients. Asymmetry of these interocular parameters may warrant repeat clinical testing for accuracy and may predict corneal abnormalities. Normative data on posterior cornea elevation is presented. This study points out potentially clinically important high interocular corneal symmetry data in simulated keratometry, corneal thickness, and posterior corneal elevation.


Am J Ophthalmol. 2004 Jul;138(1):149-51.

Brown SM, Khanani AM, McCartney DL.

Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, 3601 Fourth Street, Lubbock, TX 79430-7217, USA.

This email address is being protected from spambots. You need JavaScript enabled to view it.


PURPOSE: To investigate the effect of daily brimonidine tartrate 0.15% on the dark-adapted pupil diameter.

DESIGN: Observational case series.

METHOD: Ten normal volunteers administered brimonidine to their right eyes once daily. Four to six hours later, infrared pupil photographs were taken after dark adaptation. Measurements were performed at baseline; on treatment days 1, 5, 11, and 18; and on washout days 1 and 2.

RESULTS: One subject had no response. The nine responding subjects showed an average maximum antimydriatic effect of -1.63 mm (range, -0.57 mm--2.30 mm); all subjects experienced tachyphylaxis. Five subjects showed rebound mydriasis (mean maximum rebound +0.87 mm larger than baseline; range 0.50 mm-1.22 mm). The untreated pupil also responded, showing antimydriasis (two subjects), rebound mydriasis (two subjects), or paradoxical direct mydriasis (one subject).

CONCLUSIONS: Once-daily use of brimonidine tartrate to prevent dark-induced pupil dilation can lead to tachyphylaxis and rebound mydriasis.


Ophthalmology. 2002 Jan;109(1):175-87.

Sugar A, Rapuano CJ, Culbertson WW, Huang D, Varley GA, Agapitos PJ, de Luise VP, Koch DD.

Ophthalmic Technology Assessment Committee 2000-2001 Refractive Surgery Panel.

OBJECTIVE: This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure.

METHODS: A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies.

RESULTS: The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience.

CONCLUSIONS: For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.

Acta Ophthalmol Scand. 2003 Oct;81(5):530-2.

LASIK complication: loss of electricity to the microkeratome during the forward pass.

Tuominen IS, Tervo TM. Department of Ophthalmology, Helsinki University Hospital, PO Box 220, HUS, SF-00029 Helsinki, Finland. This email address is being protected from spambots. You need JavaScript enabled to view it.


CONTEXT: A 32-year-old woman was scheduled for myopic laser in situ keratomileusis (LASIK) because of myopia and anisometropia caused by retinal detachment surgery.

CASE REPORT: During surgery, a sudden malfunction of the microkeratome during the forward pass was experienced. It was not possible to reverse the blade manually along the suction ring. Moreover, disconnecting the suction from the control unit did not help at first, because the suction ring was firmly attached to the ocular surface. However, detaching the suction line from the control unit aborted the vacuum and allowed the surgeon to turn the whole microkeratome backwards, mimicking the normal blade movement. Finally, an almost normal flap was observed, and the operation was successfully completed. Afterwards, the wire to the electromotor of the microkeratome was found to be broken and subsequently replaced.

CONCLUSION: This type of unforeseen microkeratome malfunction may result in serious flap or other complications.

Researchers study the relation between the two.

by Matt Young EyeWorld Staff Writer


While researchers often discuss higher-order aberrations (HOAs) and whether they lead to visual symptoms, it is also worthwhile to understand which visual symptoms are related to which aberrations. Complete article is available at

From the article:

Halos were associated with spherical aberration for the scotopic pupil size.
“I find this as well,” Dr. Boxer Wachler said. “The reason is that if you look at the very center of the topography and look towards the periphery, the corneal power gets steeper. If the steeper power transition occurs relatively close to the center of topography – as in higher myopes, and/or smaller laser optical zones – this causes more spherical aberration.”
Glare also was significantly correlated with spherical aberration and total aberration. Starburst was associated with spherical aberration and total aberration for the scotopic pupil size.

The actual peer-reviewed study they are referring to appears to be this one:

Ophthalmology. 2004 Mar;111(3):447-53.

Wavefront analysis in post-LASIK eyes and its correlation with visual symptoms, refraction, and topography.

Chalita MR, Chavala S, Xu M, Krueger RR.

The Cole Eye Institute, Cleveland Clinic Foundation/I32, 9500 Euclid Avenue, Cleveland, OH 44195, USA.


PURPOSE: To evaluate the information assessed with the LADARWave wavefront measurement device and correlate it with visual symptoms, refraction, and corneal topography in previously LASIK-treated eyes.

PARTICIPANTS: One hundred five eyes (58 patients) of individuals who underwent LASIK surgery were evaluated. DESIGN: Retrospective, noncomparative case series.

MAIN OUTCOME MEASURES: Complete ophthalmologic examination, corneal topography, and wavefront measurements were performed. Correlations were made between the examinations and symptoms.

METHODS: Wavefront measurements were assessed with the LADARWave device. Manifest, cycloplegic refraction, and topographic data were compared with wavefront refraction and higher order aberrations. Visual symptoms were correlated to higher order aberrations in 3 different pupil sizes (5-mm, 7-mm, and scotopic pupil size). Pearson's correlation coefficient and generalized estimating equations were used for statistical analysis.

RESULTS: In post-LASIK eyes, wavefront refraction components were poorly correlated to manifest and cycloplegic components. The comparison between manifest, cycloplegic, and wavefront refraction with total amount of higher order aberrations showed no strong correlation. The comparison between topography and manifest, cycloplegic, and wavefront refraction did not show strong correlation. Visual symptoms analysis showed correlation of double vision with total coma and with horizontal coma for the 5-mm and 7-mm pupil size; correlation between starburst and total coma for the 7-mm pupil size; and correlation of double vision with horizontal coma, glare with spherical aberrations and with total aberrations, and starburst with spherical aberrations for the scotopic pupil size. Scotopic pupil size had a positive association with starburst and a negative association with double vision.

CONCLUSIONS: The LADARWave wavefront measurement device is a valuable diagnostic tool in measuring refractive error with ocular aberrations in post-LASIK eyes. A strong correlation between visual symptoms and ocular aberrations, such as monocular diplopia with coma and starburst and glare with spherical aberration, suggest this device is valuable in diagnosing symptomatic LASIK-induced aberrations. Horizontal coma was correlated with double vision, whereas vertical coma was not.

Volume 31, Issue 9, Pages 1764-1772 (September 2005)

Results of a randomized clinical trial

Alessandro Randazzo, MD, Francesco Nizzola, MD, Luca Rossetti, MD, Nicola Orzalesi, MD, Paolo Vinciguerra, MD


Purpose: To evaluate the efficacy and safety of diluted aceclidine eyedrops in reducing night vision disturbances after refractive surgery.

Setting: Department of Ophthalmology, Istituto Clinico Humanitas, Rozzano-Milano, Italy.

Methods: This double-masked randomized clinical trial included 30 patients (60 eyes) with chronic night vision disturbance after refractive surgery. Patients were randomly allocated to receive (1) placebo, (2) aceclidine 0.016%, or (3) aceclidine 0.032%. Drugs were administered once or twice daily. Anterior segment, haze, uncorrected visual acuity, best corrected visual acuity, intraocular pressure, corneal maps, and scotopic pupil size were determined at baseline and at follow-up examinations (15 and 30 days after inclusion). Halos and double vision 4-step scales were built to determine subjective grading of night vision disturbance, and the root mean square (RMS) was calculated to determine objective changes in night vision disturbance.

Results: The effect of diluted aceclidine started about 15 minutes after instillation and lasted for about 5 hours. No difference between the 2 dilutions could be found. Thirty-nine of 40 treated eyes showed a reduction in night vision disturbance. The mean reduction in halos and double vision grading was 1.42 ± 0.5 (SD) and 1.14 ± 0.4, respectively. A mean decrease in pupil size of 2.5 mm was measured. Thirty minutes after the instillation of diluted aceclidine, the topography-derived wavefront error showed a statistically significant reduction in RMS values (total, spherical, astigmatic, coma, and higher order), which was maintained for 5 hours. A transitory conjunctival hyperemia was the only side effect reported.

Conclusion: Diluted aceclidine seemed to be an effective and safe treatment for night vision disturbance following refractive surgery.

Journal of Refractive Surgery Volume 21 November/December 2005


Keratoconus and Corneal Ectasia After LASIK

Perry S. Binder, MS, MD; Richard L. Lindstrom, MD; R. Doyle Stulting,
MD, PhD; Eric Donnenfeld, MD; Helen Wu, MD; Peter McDonnell, MD; Yaron
Rabinowitz, MD

Excerpt: Ectasia is a known risk of laser vision correction, and if ectasia occurs in a patient following laser vision correction it does not necessarily mean that the patient was a poor candidate for surgery, that the surgery was contraindicated, or that there was a violation of the standard of care.


More On Ectasia

Post-LASIK ectasia possible with no known risk factors.

Careful preoperative screening critical; some eyes have no indication of potential problems

Oct 1, 2005
By: Cheryl Guttman
Ophthalmology Times

Dr. Shawn R. Klein did not indicate any proprietary interest. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Washington, DC

Ectasia can occur after an otherwise uncomplicated LASIK procedure, even in the absence of recognized risk factors, said Shawn R. Klein, MD, at World Cornea Congress V.

"Careful preoperative evaluation to screen out inappropriate candidates is critical for avoiding ectasia post-LASIK, but we also encourage surgeons to consider routinely measuring intraoperative stromal bed pachymetry," said Dr. Klein, clinical instructor, Institute of Ophthalmology and Visual Science, New Jersey Medical School, Newark. "However, even in the eye that appears to have no risk factors, ectasia can occur."

Dr. Klein together with Randy J. Epstein, MD, J. Bradley Randleman, MD, and R. Doyle Stulting, MD, PhD, collected a series of cases of post-LASIK ectasia that developed in the absence of risk factors. Over a 7-month period in 2003, they solicited cases through three Internet news groups.

A total of 27 eyes of 25 patients were submitted from surgeons around the world, and when rigorous criteria were applied to exclude patients with any known possible risk factors for ectasia, nine eyes of eight patients remained in the series. All were treated for low to moderate refractive errors (maximum MRSE, –8 D). Time to onset of ectasia recognition after LASIK ranged from 3 to 27 months.

The risk factor exclusion criteria consisted of: calculated residual stromal bed <250 μm, preoperative central pachymetry <500 μm, any keratometry reading >47.2 D, I - S value >1.4, attempted initial correction > –12 D, Orbscan II posterior float >50 μm (when available), > two re-treatments, and surgical/flap complications.

"We also went back to the literature to find cases of ectasia that met our study criteria and even when limiting our review to eyes with a residual stromal bed >250 μm, it was very difficult to find cases that would satisfy our rigorous exclusion criteria," Dr. Klein said. "Most of the cases in the literature had topographies that we found to be suspicious when evaluated very carefully or were lacking other data that are important for determining risk."

Three hypotheses

Dr. Klein proposed three hypotheses to account for why patients might develop ectasia despite having no apparent risk factors. One possibility is that the residual stromal bed was inadequate due to creation of an excessively thick flap and/or excessive ablation.

"Intraoperative data from stromal bed pachymetry were only available for one of the nine eyes in our series and so we did not know flap thickness for most of the cases," he noted.

Dr. Klein also proposed that these patients may have had preoperative topographic abnormalities that were undetected because the machines were not sensitive enough or not used correctly. Supporting that possibility is the fact that the submitted scans for some of the patients were of limited detail, making I - S calculations difficult.

According to Dr. Klein, a third possibility is "most tantalizing," and that is that these patients have biomechanically unstable corneas with no preoperative abnormalities detectable using widely available technology.

"I like to think of these cases as a forme fruste keratoconus and that they are unable to withstand the insult of LASIK," Dr. Klein said.

Of interest with respect to that concept, in an analysis of the demographic and operative data for the series of eight cases, age emerged as a potentially remarkable factor for the group. The eight patients in the series were found to be significantly younger than the mean age reported in a previously published series [Randleman, et al. Ophthalmology 2000;110:267-275] for both patients who developed ectasia and control groups.

"Perhaps some of these patients might have eventually developed keratoconus even if they had not undergone LASIK, but the surgery accelerated the onset," Dr. Klein explained. "However, our data suggest that the risk of ectasia in the absence of known risk factors may be higher in younger patients."

Dr. Klein also noted that as one of its limitations, the cases in this retrospective study were contributed by multiple different surgeons who used different techniques and technology, including a number of different microkeratomes, lasers, and pachymeters.

  after wavefront-guided LASIK

J Cataract Refract Surg. 2005 Dec;31(12):2272-80.  

Buhren J, Kuhne C, Kohnen T.  From the Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.  

PURPOSE: To investigate the influence of pupil and optical zone (OZ) diameter on higher-order aberrations (HOAs) after myopic wavefront-guided laser in situ keratomileusis (LASIK).  

METHODS: Twenty-seven myopic eyes of 19 patients were included. The mean preoperative spherical equivalent was -6.86 diopters (D) +/- 1.24 (SD) (range -4.25 to -9.5 D); the mean planned OZ diameter was 6.26 +/- 0.45 mm (range 5.7 to 7.1 mm). All patients had uneventful wavefront-guided LASIK (Zyoptix version 3.1, Bausch & Lomb) and an uncomplicated follow-up of 12 months. Wavefront measurements were performed with a Hartmann-Shack sensor in maximum mydriasis preoperatively and 12 months after LASIK. Wavefront errors were computed for pupil diameters (PDs) of 3.0, 3.5, 4.0, 5.0, 6.0, and 7.0 mm for the individual OZ diameter and for the individual mydriatic PD (7.93 +/- 0.46 mm). The impact of the relationship between pupil diameter and OZ diameter (fractional clearance [FC]) on HOA was described and quantified using curvilinear regression with a 4th-order polynomial fit.  

RESULTS: There was a reproducible relationship between FC and the amount of induced HOA. The change in HOA root mean square and primary spherical aberration (Z(4)(0)) was significantly correlated with FC. If the OZ was 16.5% larger than the pupil (FC = 1.17), only half the amount of HOA was expected to be induced than if the OZ equaled the pupil. In contrast, an OZ that was 9% smaller than the pupil (FC = 0.91) resulted in an HOA induction 50% higher than at FC = 1.  

CONCLUSION: The OZ zone to pupil ratio (fractional clearance) had a significant impact on HOA induction after wavefront-guided LASIK.


J Cataract Refract Surg. 2005 Aug;31(:1537-43.

Garamendi E, Pesudovs K, Elliott DB.

Department of Optometry, University of Bradford, Richmond Road, Bradford, West Yorkshire, United Kingdom. This email address is being protected from spambots. You need JavaScript enabled to view it.


PURPOSE: To measure quality of life (QoL) outcome in prepresbyopic myopic patients having laser in situ keratomileusis (LASIK) refractive surgery using the Quality of Life Impact of Refractive Correction (QIRC) questionnaire and to compare the QoL of preoperative patients with a sample of spectacle and contact lens wearers not considering refractive surgery.


SETTING: Department of Optometry, University of Bradford, Bradford, and Ultralase, Leeds, West Yorkshire, United Kingdom.


METHODS: The validated QIRC questionnaire was prospectively completed by 66 patients before and 3 months after LASIK. Patients had myopia greater than 0.50 diopters (D) (range --0.75 to --10.50 D) and were aged 16 to 39 years. Patients were also directly asked to evaluate their QoL after surgery.


RESULTS: Overall QIRC scores improved after LASIK from a mean of 40.07+/- 4.30 (SD) to 53.09+/- 5.25 (F(1,130)=172.65, P<.001). Greater improvements occurred in women (53.83+/- 5.46) than in men (49.39+/- 5.94; F(1,64)=9.37, P<.005). Overall, 15 of the 20 questions (especially convenience, health concerns, and well-being questions) showed significantly improved scores (P<.05). Patients who "strongly agreed" (53.96+/- 4.91, n=33) or "agreed" (51.78+/- 6.19, n=23) had improved QoL and had significantly higher QIRC scores than those who "neither agreed nor disagreed" (44.36+/- 4.97, n=5) or "strongly disagreed" (42.82, n=1) (F(1,60)=11.24, P<.001). The matched group not contemplating LASIK scored 42.41 +/- 3.89 on QIRC overall.


CONCLUSIONS: Large improvements in QIRC QoL scores were found after LASIK for myopia in the majority of patients, with greater improvements in women. A small number of patients (4.5%) had decreased QIRC QoL scores, and these were associated with complications. People presenting for LASIK scored measurably poorer than matched patients not contemplating refractive surgery.


Now for the truth behind the survey (from the full-text):

"the optical zone was at least 6.0 mm, increased to 0.5 mm greater than the scotopic pupil for pupils over 5.5 mm".

"... other factors, such as the Hawthorne effect and cognitive dissonance, should be considered. Participating in a clinical trial or study can make patients report a significant positive effect of the surgery due to the added attention being made toward them (the Hawthorne effect)."

"Cognitive dissonance states that a change in attitude or belief occurs in an attempt to be consistent with the choice taken. Patients who have chosen to have surgery could justify this choice by indicating that the outcome was successful".


Klin Monatsbl Augenheilkd. 2005 May;222(5):419-23.

[Article in German]

Schafer S, Kurzinger G, Spraul CW, Kampmeier J.

Augenklinik, Universitatsklinikum Ulm. 



BACKGROUND: Postoperative hyperopia is a frequent result of cataract surgery in eyes after previous myopic kerato-refractive surgery. One reason for the underestimation of intraocular lens (IOL) power is the wrong corneal refractive power measurement obtained by keratometers and corneal topography systems after LASIK. The aim of this study was to compare the precision of measurements of three different keratometers after LASIK.


METHOD: We studied 58 eyes of 34 refractive patients aged between 20 and 51 years. The preoperative measurements and the measurements one month after LASIK were performed with the Keratometer (Zeiss), the corneal topograph (EyeSys Technologies) and the IOL-Master (Zeiss). We compared our postoperative measurement results obtained with the three keratometers with the results obtained by using the clinical history method (chm).


RESULTS: The smallest mean deviation was achieved with the IOL-Master (measured mean +/- SD: 38.94 +/- 1.88 D, vs. chm: 38.35 +/- 2.13 D). The Keratometer (Zeiss) showed a larger deviation (measured: 39.12 +/- 1.76 D, chm 38.34 +/- 2.07 D) and the largest deviation was shown with the corneal topograph (measured: 39.84 +/- 1.85 D, chm: 38.86 +/- 2.10 D), which measured in mean one diopter higher than what was obtained utilizing the chm. A positive correlation between corrected myopia and the postoperative difference between the measured and calculated value for each keratometer was found.


CONCLUSION: This study demonstrates that with common keratometers central corneal power is measured too high after LASIK. For IOL calculation in patients after LASIK, the wrongly positive deviation from measured central corneal power has to be taken into account.

Journal of Cataract & Refractive Surgery

Volume 31, Issue 2 , February 2005, Pages 379-384

"Glare is induced by rays of light that enter the pupil through the portion of the cornea outside the ablation area. A larger pupil allows more errant light rays to reach the retina and degrade the perceived image. For this reason, a larger ablation zone is required in patients with large pupils and high myopic corrections".