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Objective: The purpose of the study is to determine safety and efficacy outcomes of excimer laser photorefractive keratectomy (PRK) for the treatment of mild-to-moderate myopia. Design: A prospective, multicenter, phase III clinical trial. Participants: A total of 701 eyes of 701 patients were entered in the study; 612 eyes were examined at 2 years after surgery. Intervention: Intervention was photorefractive keratectomy using the Summit ExciMed UV200LA excimer laser (Summit Technology, Inc., Waltham, MA). The treatment zone diameter used was 4.5 mm in 251 eyes (35.8%) and 5 mm in 450 eyes (64.2%). Attempted corrections ranged from 1.50 to 6.00 diopters (D). Main Outcome Measures: Predictability and stability of refraction, uncorrected and spectacle-corrected visual acuity, refractive and keratometric astigmatism, corneal haze, contrast sensitivity, subjective reported problems of glare and halo, and patient satisfaction were the parameters measured. Results: At 2 years, 407 (66.5%) eyes achieved 20/20 or better uncorrected visual acuity and 564 (92.5%) eyes achieved 20/40 or better visual acuity. Three hundred thirty-six (54.9%) eyes were within 0.5 D and 476 (77.8%) eyes were within 1.0 D of attempted correction. Stability of refraction improved with time; 86.8% of eyes were stable within 1.0 D from 6 to 12 months, 94% were stable from 12 to 18 months, and 96.3% were stable from 18 to 24 months. There was no evidence of progressive or late myopic or hyperopic refractive shifts. One hundred fourteen (18.6%) eyes gained 2 or more lines of spectacle-corrected visual acuity, whereas 42 (6.9%) eyes lost 2 or more lines; however, of the latter, 32 (76.2%) had spectacle-corrected visual acuity of 20/25 or better and 39 (92.9%) eyes had 20/40 or better. Four hundred forty-two (72.2%) corneas were clear, 138 (22.5%) showed trace haze, 20 (3.3%) mild haze, 9 (1.5%) moderate haze, and 3 (0.5%) marked haze. On patient questionnaires, 87 (29.7%) patients reported worsening of glare from preoperative baseline; 133 (50.1 %) reported worsening of halo symptoms from baseline. Conclusions: Photorefractive keratectomy appears effective for myopic corrections of −1.50 to −6.00 D. Uncorrected visual acuity is maximized in most eyes by 3 months, although some patients require between 6 months and 1 year to attain their best postoperative uncorrected visual acuity and some may require from 1 to 2 years for stabilization of refraction. Refraction stabilizes progressively without evidence of late myopic or hyperopic refractive shifts. Optical sequelae of glare and halo occur in some patients treated with a 4.5- or 5-mm treatment zone.

Purpose: To identify preoperative and intraoperative characteristics associated with outcomes of photorefractive keratectomy (PRK). Methods: In the phase III multicenter clinical trials of the Summit Technology excimer laser for corrections of 1.5 to 6.0 diopters (D) of myopia, three principal outcomes of PRK on 612 patients were examined: (1) uncorrected visual acuity of 20/40 or better, (2) predictability of refractive outcome within 1.0 D of attempted correction, and (3) stability of refractive result between 12 and 24 months. Multiple logistic regression was used to test for independent associations of multiple preoperative and intraoperative characteristics with each of these outcomes. Results: Older age was independently associated with lesser likelihood of achieving 20/40 or better uncorrected visual acuity (odds ratio=1.08 per incremental year of age, 95% confidence interval [Cl] = 1.04–1.12) and with decreased predictability, specifically with overcorrection (odds ratio=1.09, 95% Cl=1.06–1.12), but age was not associated with stability of refraction. Greater attempted correction was associated independently with a decreased likelihood of 20/40 or better uncorrected visual acuity (odds ratio=2.78 for corrections of 3.5–5.5 D, 95% Cl=1.18–6.75; odds ratio=4.19 for corrections of ≥5.5 D, 95% Cl=1.66–10.58), with decreased predictability (odds ratio=1.72 for corrections of 3.5–5.5 D, 95% Cl=1.05–2.85; odds ratio=2.95 for corrections of ≥5.5 D, 95% Cl=1.65–5.26), and with a reduced likelihood of stability of refraction (odds ratio=3.46 for corrections of ≥5.0 D, 95% Cl=1.32–9.11). No intraoperative characteristics were associated with any of the outcomes assessed. Conclusions: Using this specific excimer laser system with an optical zone of 4.5 or 5.0 mm, patient age and attempted correction are important preoperative characteristics associated with postoperative uncorrected visual acuity and predictability of PRK. Stability of refraction is strongly associated with attempted correction. Such information may help guide patient selection, determine timing of fellow eye treatment, and suggest changes in the laser treatment algorithm for individual patients. Although these findings may be representative of PRK in general, similar analyses should be performed before modifying patient treatments using either a 6.0-mm treatment zone or other laser systems.

Purpose: To define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK), assess changes in patterns, associations with clinical outcomes, and the accuracy of videokeratography in predicting results, and define quantitatively the optical zone contour. Methods: Computer-assisted videokeratography data obtained from 181 patients after PRK was analyzed. Topography patterns at two time points were characterized, and associations with clinical outcomes were tested. Power change predicted by topography was compared with refractive change, and cross-sectional power contours were analyzed. Results: Seven topography patterns were defined. At 1 year, 58.6% of corneas showed a homogeneous topography, 17.7% showed a toric-with-axis configuration, 2.8% showed a toric-against-axis configuration, 13.8% showed an irregularly irregular topography, 2.8% showed a keyhole/semicircular pattern, and 4.4% showed focal topographic variants. No central island patterns were found. Of the maps, 41 % changed over time. Uncorrected vision, predictability, and patient satisfaction were best in the homogeneous group. Astigmatism increased in the irregular and toric-against-axis groups and decreased in the toric-with-axis group. There was no relation of topography pattern to best-corrected vision or subjective glare/halo. Cross-sectional power profiles showed a homogeneous power change for the central 3 mm with a diminution in correction toward the periphery. The topography unit tended to overestimate refractive change for corrections of 5 diopters or less and underestimate the change for corrections greater than 5 diopters. Conclusions: Topography patterns after PRK are identifiable, time dependent, and may affect clinical outcomes. Understanding the actual corneal optical contour resulting from PRK may aid in improving both laser techniques and optical results in the future.

Peribulbar anesthesia was performed in 407 patients and retrobulbar anesthesia in 441 patients in a prospective study comparing the efficacy and complication rate of the two procedures. Eighteen of the peribulbar procedures (4.4%) required reblocks. There were no major complications in this group. Thirty of the retrobulbar procedures (6.8%) required reblocks. This group also had no major complications. The chi-square method of statistical analysis (chi-square = 2.245; P = .134) indicates there was no statistically significant difference between the efficacy of the two local anesthesia methods.