Iatrogenic keratectasia after a deep primary keratotomy during laser in situ keratomileusis.

PURPOSE: To describe a case of keratectasia after a deep primary keratotomy during an aborted laser in situ keratomileusis procedure. METHODS: Retrospective, observational case report. RESULTS: In a 47-year-old woman, progressive keratectasia developed after a 90% depth keratotomy during an aborted laser in situ keratomileusis procedure. This case was managed with a rigid gas permeable contact lens and consideration for penetrating keratoplasty. CONCLUSION: Keratectasia is a reported microkeratome-related complication after laser in situ keratomileusis. Appropriate microkeratome assembly and surgeon awareness are necessary to avoid this complication.

Effect of preoperative pupil measurements on glare, halos, and visual function after photoastigmatic refractive keratectomy.

PURPOSE: To prospectively assess the effect of preoperative variables such as pupil size on glare, halos, and visual function after photoastigmatic refractive keratectomy (PARK). SETTING: Department of Ophthalmology, Stanford University School of Medicine, Stanford, California, USA. METHODS: Ninety-three eyes had PARK for primary compound myopic astigmatism. Preoperative pupil diameters were measured under scotopic and photopic illuminance conditions. Postoperatively, patients were evaluated at 1, 3, 6, 9, 12, 18, and 24 months. A regression model was performed to evaluate the predictive value of assessing preoperative variables such as pupil diameter on the development of glare and halos, contrast sensitivity, and best spectacle-corrected visual acuity (BSCVA) under scotopic, photopic, and glare conditions. RESULTS: The greater magnitude loss of BSCVA under scotopic conditions in the early postoperative period as well as the slower recovery to preoperative levels in eyes with larger scotopic pupil diameters were not statistically significant (P >.05). An increase in symptoms of glare was related more to the attempted level of spherical equivalent (SE) correction than to the pupil size during the first 12 postoperative months (P <.01). The photoablation dimensions as determined by the attempted level of astigmatic correction may result in decreases in the glare BSCVA up to 12 months after PARK (P =.03). At the 2 year follow-up, pupil diameter under both scotopic and photopic illuminance conditions was not predictive of any of the measured outcomes variables. CONCLUSIONS: An assessment of preoperative pupil size and the attempted level of both SE and astigmatic correction may be useful in identifying patients at risk of developing symptoms or declines in visual performance after PARK. However, follow-up studies are indicated to identify variables predictive of poor visual outcomes following excimer laser refractive surgery.

Treatment of progressive or recurrent epithelial ingrowth with ethanol following laser in situ keratomileusis.

PURPOSE: To evaluate the use of ethanol in the treatment of progressive or recurrent epithelial ingrowth following laser in situ keratomileusis (LASIK). METHODS: Four eyes of four patients with aggressive epithelial ingrowth following LASIK underwent epithelial ingrowth removal with 50% ethanol. Aggressive epithelial ingrowth was defined as, 1) progressive enlargement on serial examination with an area of ingrowth involving at least 30% of the flap surface area, 2) epithelial ingrowth associated with stromal melting as evidence on clinical or topographic examination, or 3) recurrent epithelial ingrowth in the same area following previous removal. RESULTS: Epithelial ingrowth was removed successfully in all eyes. No eye lost best spectacle-corrected visual acuity. One eye with multiple risk factors for failure experienced nonprogressive recurrence. No eyes required reoperation for recurrent epithelial ingrowth. No eyes experienced progression of stromal melt. Regularization of corneal topography was observed in an eye with preoperative stromal melting. The only complication was a tendency for the development of diffuse lamellar keratitis. Two eyes (50%) experienced diffuse lamellar keratitis following epithelial ingrowth removal with ethanol, which resolved completely with topical corticosteroids. CONCLUSION: Ethanol may be a useful adjunct in the treatment of aggressive or recurrent epithelial ingrowth following LASIK. Cautious use with the lowest concentration of ethanol may prove useful in these difficult epithelial ingrowth cases. Randomized and prospective studies are recommended to evaluate our experience.

Prospective study of photorefractive keratectomy for hyperopia using an axicon lens and erodible mask.

PURPOSE: To evaluate prospectively the long-term safety, efficacy, and visual performance following photorefractive keratectomy (PRK) for hyperopia using an erodible mask and axicon lens system. METHODS: Eighteen eyes of 9 patients with a mean preoperative spherical equivalent refraction of +2.26 +/- 0.82 D (range, +1.13 to +4.00 D) underwent PRK with the Summit Apex Plus excimer laser following manual scraping of the epithelium. Eyes were prospectively evaluated 1, 3, 6, 9, 12, 18, and 24 months following the procedure. Primary outcome variables included cycloplegic refraction and uncorrected visual acuity (UCVA). Visual performance was determined by contrast sensitivity measurements under scotopic (21 lux) and photopic (324 lux) conditions and best spectacle-corrected visual acuity (BSCVA) under scotopic, photopic, and glare conditions. RESULTS: For 18 eyes, 98.2% of the mean preoperative spherical equivalent refraction was corrected to +0.04 +/- 0.87 D (range, -1.38 to +2.00 D) at 24 months after PRK. Twelve eyes (67%) were within +/-0.50 D of attempted correction and 15 eyes (83%) were within +/-1.00 D. Stability within +/-0.50 D was achieved after 6 months. Two eyes (11%) experienced almost complete regression of the refractive effect. There was no statistically significant decrease in contrast sensitivity under scotopic or photopic conditions. (P > .05). Best spectacle-corrected visual acuity showed progressive improvement in the early postoperative period. By 24 months, 0 eyes (0%) lost 2 or more lines of BSCVA under scotopic and photopic conditions and 1 eye (5.5%) lost 2 or more lines under glare conditions. Fourteen eyes (78%) had grade 1 to 3 anterior stromal haze at 24 months which was characteristically mid-peripheral and did not adversely affect visual performance. CONCLUSION: Photorefractive keratectomy with the the Summit Apex Plus excimer laser for low to moderate hyperopia resulted in an effective reduction of hyperopia without compromising long-term visual performance. Stability and recovery of distance uncorrected and best spectacle-corrected visual acuity took approximately 6 months.

Late onset diffuse lamellar keratitis associated with an epithelial defect in six eyes.

PURPOSE: To report six cases of late onset diffuse lamellar keratitis associated with epithelial defects 2 to 12 months following uncomplicated laser in situ keratomileusis (LASIK). METHODS: Retrospective case series. RESULTS: The interface inflammation and epithelial defects were treated aggressively with topical corticosteroids and topical antibiotics with complete resolution over 1 to 2 weeks. There were no complications or loss of best spectacle-corrected visual acuity. These cases illustrate new understanding in the etiology of diffuse lamellar keratitis following lamellar surgery. CONCLUSION: Late onset diffuse lamellar keratitis in association with epithelial defects may occur following LASIK. Treatment with topical antibiotics and topical corticosteroids may result in uncomplicated, complete resolution.

Visual performance following photoastigmatic refractive keratectomy: a prospective long-term study.

PURPOSE: To prospectively determine the long-term effect of excimer laser photoastigmatic refractive keratectomy (PARK) on visual performance using psychophysical assessments and to identify predictors of poor performance on the psychophysical assessments. SETTING: University-based hospital, Stanford University, Stanford, California, USA. METHODS: Ninety-three eyes of 56 patients with a mean of -4.98 diopters +/- 1. 80 (SD) of primary compound myopic astigmatism had PARK using the Summit Apex Plus excimer laser and an erodible mask system. Patients were prospectively evaluated 1, 3, 6, 9, 12, 18, and 24 months following the procedure. Primary outcome variables included changes in the contrast sensitivity function curve (3.0, 6.0, 12.0, 18.0 cycles per degree) under 2 standard illuminance conditions (scotopic and photopic) and changes in the best spectacle-corrected visual performance under scotopic, photopic, and glare conditions. RESULTS: A relative decline in the contrast sensitivity function curve occurred in the early postoperative period under both scotopic and photopic conditions. This was most pronounced under photopic illuminance and at the low spatial frequencies at the 6 month visit. By 1 year, however, the mean contrast sensitivity at all spatial frequencies and all illuminance conditions had returned to the preoperative level. Further improvements beyond the preoperative level may be related to the independent analysis of retreatment eyes beyond 6 months. A higher level of attempted correction of the spherical equivalent was predictive of an elevated scotopic contrast threshold at the extreme spatial frequencies 6 months after PARK (P <.05). The attempted level of astigmatic correction was predictive of a poor best corrected visual performance under scotopic conditions at 1 month (P <.05). This effect was only temporary and by postoperative month 3, there was no predictive effect of preoperative astigmatism (P >.05). CONCLUSIONS: Psychophysical assessments may be a more sensitive indicator of decreases in visual performance following excimer laser refractive surgery. The attempted level of correction of spherical equivalent and astigmatism may adversely affect early scotopic visual performance. Decreases in visual performance are temporary, return to normal by 12 months, and remain stable 24 months following PARK.

Photorefractive keratectomy for compound myopic astigmatism.

PURPOSE: To evaluate the safety and efficacy of photorefractive keratectomy for the treatment of primary compound myopic astigmatism. METHODS: In a prospective study, 93 eyes from 56 patients with a mean spherical equivalent of -4.98 +/- 1.80 diopters (range, -1.75 to -8.5) underwent photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser using erodible mask technology and were followed for 2 years. Primary outcome measures included an assessment of astigmatic correction through vector analysis, manifest refraction, uncorrected visual acuity, corneal clarity, and the presence of adverse symptoms. RESULTS: Eighty-five eyes (91.4%) were available for analysis at 6 months. Mean spherical equivalent refraction was reduced 85% (mean, -0.75 +/- 0.85 diopter) and the target-induced astigmatism was reduced 70% (mean, 0.98 +/- 1.88 diopters). Forty-eight eyes (56%) had an uncorrected visual acuity of 20/20 or greater, whereas 70 eyes (82%) had an uncorrected visual acuity of 20/40 or greater. Twenty-four eyes (26% ) required re-treatment because of undercorrection of the spherical equivalent and astigmatic components after the 6-month follow-up. Fifty-nine of the remaining eyes were available at the 24-month visit. Mean spherical equivalent refraction was reduced to -0.39 +/- 0.72 diopter (91.8%). The target-induced astigmatism was reduced 64% from 1.74 diopters. Forty-one eyes (81.3%) were within +/-1.0 diopter of attempted spherical equivalent correction. Stability within a spherical equivalent of +/-0.5 diopter occurred after the first postoperative month. Fifty-six eyes (94.9%) had an uncorrected visual acuity of 20/40 or greater, whereas 34 eyes (57.6 %) demonstrated an uncorrected visual acuity of 20/20 or greater. One eye (1.7%) lost 2 or more lines of best spectacle-corrected visual acuity. CONCLUSION: Photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser is a safe and effective method of reducing compound myopic astigmatism. However, higher re-treatment rates may result from significant undercorrections because of current laser algorithms and variability in the mean angle of error.

One-year evaluation of myopic laser photoastigmatic refractive keratectomy using the summit apex plus: phase III of a Food and Drug Administration clinical trial.

PURPOSE: To prospectively evaluate the safety and efficacy of the Summit Apex Plus excimer laser in the treatment of primary compound myopic astigmatism. DESIGN: Prospective noncomparative interventional case series. PARTICIPANTS: Patients with primary compound myopic astigmatism: sphere of -1.0 to -7.0 diopters (D) and cylinder -1.0 to -5.0 D. METHODS: Ninety-three eyes of 56 patients with a mean spherical equivalent of -4.98 +/- 1.80 D (-1.75 to -8.5) underwent photoastigmatic refractive keratectomy (PARK) with the Summit Apex Plus excimer laser using erodible mask technology. Prospective follow-up is analyzed at 1-year postoperatively. MAIN OUTCOME MEASURES: Postoperative reduction in myopic sphere, myopic astigmatism, spherical equivalent, angle of error, magnitude of error, difference vector, uncorrected visual acuity, and corneal haze. RESULTS: Seventy-one eyes were available at 1-year follow-up. Mean spherical equivalent was reduced 86.5% to a mean residual of -0. 65 D +/-0.70 D (-2.88-+1.13 D). Astigmatism was reduced 66.2% to a mean residual of -0.76 +/- 0.52 D (-2.25-0.00 D); 77.5% were within 1.0 D of attempted correction; 1.4% of eyes experienced an overcorrection >1.0 D of spherical equivalent; 0.27 D of mean myopic regression was demonstrated between 1 and 12 months; 93.0% of eyes achieved an uncorrected visual acuity of 20/40 or better; and 49.3% of eyes achieved an uncorrected visual acuity of 20/20 or better. CONCLUSIONS: PARK with the Summit Apex Plus excimer laser is effective at reducing compound myopic astigmatism. However, current laser algorithms result in consistent undercorrection of both the compound myopia and the astigmatic component.

Excimer laser retreatment of residual myopia following photoastigmatic refractive keratectomy for compound myopic astigmatism.

PURPOSE: To prospectively evaluate the safety, efficacy, and visual performance of excimer laser enhancement following photoastigmatic refractive keratectomy (PARK) with the Summit Apex Plus. SETTING: Stanford University School of Medicine Eye Laser Clinic, Stanford, California, USA. METHODS: As part of a Food and Drug Administration clinical trial, 93 eyes of 56 patients with a mean spherical equivalent (SE) of -4.98 diopters (D) +/- 1.80 (SD) (range -1.75 to -8.50 D) had PARK for compound myopic astigmatism using the Summit Apex Plus excimer laser and a poly(methyl methacrylate) erodible mask. Seventeen eyes with a mean SE of -2.08 +/- 0.76 D required excimer laser refractive keratectomy for residual spherical myopia or compound myopic astigmatism. Patients were prospectively followed 1, 3, 6, 9, and 12+ months after the enhancement procedure. Primary outcome variables included uncorrected visual acuity (UCVA), refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA) under standard ambient conditions (photopic, scotopic, and glare), corneal clarity, and contrast sensitivity function curve under photopic and scotopic conditions. RESULTS: At the last postoperative visit, the mean sphere had been corrected 82% to a residual of -0.29 +/- 1.23 D and mean SE had been corrected 65% to a residual of -0.74 +/- 1.27 D. Eighty-two percent of eyes were within +/-1.0 D of attempted correction. Eighty-eight percent had a UCVA of 20/40 or better. Vector analysis demonstrated a difference vector of within +/-1.0 D in 75% of eyes that had PARK retreatment. There was no significant loss in the contrast sensitivity curve. Late regression associated with corneal haze and loss of BSCVA occurred in 2 eyes (11.7%). CONCLUSIONS: Retreatment following PARK for compound myopic astigmatism results in effective reduction in residual spherical myopia and compound myopic astigmatism. An improvement in UCVA without loss of contrast sensitivity can be expected in most eyes. However, regression, corneal haze, and loss of BSCVA may occur. Further studies are indicated to predict risk factors for these complications.

Large optical ablation zone using the VISX S2 smoothscan excimer laser.

PURPOSE: To prospectively evaluate the safety and efficacy of the new large-zone (6.5 mm) photoablation technology using the VISX S2 Smoothscan excimer laser. SETTING: University-based hospital, Stanford, California, USA. METHODS: Forty-two eyes of 21 patients with a mean preoperative spherical equivalent (SE) of-5.55 diopters (D)+/- 2.24 (SD) (range-2.13 to-10.75 D) had laser in situ keratomileusis (LASIK) using the VISX Smoothscan S2 excimer laser for simple myopia or compound myopic astigmatism. A 6.5 mm optical zone was used in all eyes. Patients were prospectively followed 1 day and 1 and 3 months postoperatively. RESULTS: At 3 months, the mean SE was reduced 94% to-0. 31+/- 0.55 D. Ninety-one percent of eyes had an uncorrected visual acuity of 20/40 or better. Eighty-eight percent were within+/-1.00 D of attempted correction and 84%, within +/-0.50 D. Stability within+/-0.50 D occurred after the first postoperative month. Vector analysis of eyes that had toric ablations demonstrated a difference vector within+/-1.00 D in 100% of eyes. The mean angle of error was-0.04+/- 6.37 degrees. Visually significant steep central islands associated with loss of best spectacle-corrected visual acuity was observed in 7.5% of eyes at 1 month. No eyes experienced significant glare or halos. CONCLUSIONS: The new large-zone (6.5 mm) photoablation technology with the VISX S2 Smoothscan resulted in effective reduction of simple myopia and compound myopic astigmatism. However, with the 6.5 mm zone, there may be an increased risk of developing symptomatic steep central islands in the early post-LASIK period compared with the standard 6.0 mm treatment zone.

Sterile peripheral keratitis following laser in situ keratomileusis.

BACKGROUND: Sterile infiltrates have been reported as a possible complication following photorefractive keratectomy (PRK). They have not been reported following laser in situ keratomileusis (LASIK). We review a case of fleeting, sterile peripheral corneal infiltrates following LASIK. METHODS: A 53 year old patient developed peripheral, sterile corneal infiltrates along the edge of the primary flap following LASIK. This was successfully managed with topical antibiotics and corticosteroids without permanent sequelae. RESULTS: Sterile peripheral corneal infiltrates are now a known complication following LASIK. Pathogenesis is undetermined but may involve activation of marginal keratitis reminiscent of that following blepharitis or a mechanism similar to acute subepithelial infiltrative keratitis following PRK. CONCLUSION: Fleeting, sterile peripheral corneal infiltrates can occur following LASIK. This undesired complication is poorly characterized but can be successfully managed with culturing of the infiltrates, topical corticosteroids, and antibiotics.

Excimer laser refractive surgery.

Excimer laser photorefractive keratectomy and excimer laser in situ keratomileusis are relatively new treatment modalities that can be used to correct refractive errors of the eye. They are most commonly used to correct myopia (nearsightedness) but can also be used to correct hyperopia (farsightedness) and astigmatism. The excimer laser alters the refractive state of the eye by removing tissue from the anterior cornea through a process known as photoablative decomposition. This process uses ultraviolet energy from the excimer laser to disrupt chemical bonds in the cornea without causing any thermal damage to surrounding tissue. The modified anterior corneal surface enables light to be focused on the retina, thereby reducing or eliminating the dependence on glasses and contact lenses. We discuss in detail all aspects of excimer laser refractive surgery--techniques, indications and contraindications, clinical outcomes, and complications.