Predictive factors for efficacy and safety in refractive surgery for myopia.

PURPOSE: To evaluate the predictive factors for safety and efficacy in laser refractive surgery for myopia. SETTING: A singular refractive surgery center, at a University-affiliated tertiary medical center. DESIGN: Retrospective cohort study. METHODS: Study population-A total 8,775 eyes having laser refractive laser procedures for myopia (in4,623 patients). Observation procedures-Using a prospective database of refractive procedures performed over the span of 13 years, variables such as gender, age, type of surgery, date of surgery, pre-operative corneal thickness and Spherical Equivalent (SEQ) were evaluated. Main outcome measures-Proportion of patients with Safety index higher than 0.85 and Efficacy index higher than 0.80. RESULTS: 91.9% and 86.0% of all evaluated eyes were above the safety and efficacy cut-off levels, respectively. Younger age was significantly correlated with safety and efficacy indices above the cut-off levels (p<0.001). Male gender was significantly correlated with efficacy above the cut-off level (p<0.001). Myopic eyes with lower SEQ were associated with both safety (p = 0.002) and efficacy (p<0.001) indices above the cut-offs. The surgical procedure was found to significantly affect the outcome only using univariate analysis: Safety was higher in Photorefractive Keratectomy (PRK), while Efficacy was higher in Laser Assisted In Situ Keratomileusis (LASIK) (p<0.001, respectively) but no difference was found using multivariate analysis. Safety index above the cut-off level increased over the years (p<0.001). CONCLUSIONS: Efficacy in refractive surgery for myopia is correlated with younger age, male gender and low myopia. Safety is correlated with younger age, low myopia and increases over the years. Multivariate analysis found no differences between PRK and LASIK regarding safety and efficacy.

Mathematical approximation of Orbscan II central corneal thickness to contact ultrasound.

PURPOSE: To compare Orbscan II central corneal thickness (CCT) measurements corrected by five mathematical methods with ultrasound (US) CCT measurements. METHODS: The preoperative CCT examinations of the right eyes of 3242 consecutive candidates for refractive surgery were retrospectively reviewed. Raw Orbscan data were processed by five correction methods: multiplication, subtraction, polynomial, logarithmic, and power. For each correction method, the concordance between corrected Orbscan and US pachymetries was assessed by mean, Pearson correlation, regression analysis, 95% limits of agreement (LoA), and percentage of eyes within 8 µm of US pachymetry. RESULTS: Throughout the 3242 eyes analyzed, we found a high Pearson correlation between Orbscan and US measurements with all correction methods assessed. The linear multiplication and subtraction correction methods brought about mean Orbscan CCT similar to mean US CCT measurements. However, they led to relatively high 95% LoA intervals and low percentage of eyes within 8 µm of US pachymetry. In contrast, the three nonlinear correction methods proposed herein for the first time narrowed the 95% LoA interval (Bland-Altman analysis) together with providing mean Orbscan CCT similar to mean US CCT measurements. Moreover, the power fit was the only method that was reproducible when extracted from one subset of the cohort and applied in another. CONCLUSIONS: Broad 95% LoA intervals were obtained when applying the multiplication and the subtraction correction methods, indicating a poor agreement between the devices. We suggest the power fit as the default method for adjusting Orbscan to US CCT readings.

Early transient visual acuity loss after LASIK due to steroid-induced elevation of intraocular pressure.

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.

Traumatic corneal flap dislocation one to six years after LASIK in nine eyes with a favorable outcome.

PURPOSE: To report our experience treating eye trauma after LASIK refractive surgery. METHODS: Nine eyes of eight patients (one woman and seven men) were treated for ocular trauma: blunt trauma (n=5), sharp instrument trauma (n=2,) and trauma from inflation of automobile air bags during a traffic accident (n=2). The time from LASIK varied between 3 months and 6 years. All patients were hospitalized as a result of severe decrease in visual acuity and pain. RESULTS: Seven of nine LASIK flaps had some degree of dislocation and were lifted, irrigated, and repositioned. Two flaps were edematous without dislocation. Intensive topical steroids and antibiotics were used in all patients up to 3 weeks after trauma. Three months after trauma, five eyes regained their pre-trauma visual acuity (between 20/20 and 20/40), and three eyes lost one line of best spectacle-corrected visual acuity. CONCLUSIONS: Trauma occurring several months or years after LASIK may cause flap injury. Adequate and prompt treatment usually is successful.