PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA USING A 4.5-MILLIMETER ABLATION ZONE

BACKGROUND: Argon fluoride (193 nm) excimer laser photorefractive kera tectomy for myopia is under evaluation by the United States Food and D rug Administration. METHODS: We report a consecutive prospective serie s of 100 patients (one eye per patient) treated as part of the Phase I IB FDA-approved protocol, with 80 patients followed for 1 year. Patien ts' ages ranged from 21 to 62 years (mean, 35 years). The Summit Techn ology, Inc ExciMed(R) UV200LA with a 4.5-mm diameter ablation was used . RESULTS: Baseline spherical equivalent refraction ranged from - 2.00 to - 6.90 diopters (D) (mean -4.60 D). Ninety-five percent of eyes re epithelialized by 72 hours. At 1 year, the difference between attempte d and achieved correction was +/- 0.50 D for 42 eyes (53%) and +/- 1.0 0 D for 60 eyes (75%). During the first 6 months, there was a trend to ward overcorrection and the majority of eyes showed some loss of initi al refractive correction; 10 eyes (14%) changed by 1.00 D or more betw een 6 and 12 months. An uncorrected visual acuity of 20/25 or better w as achieved by 50 eyes (63%) and 20/40 or better by 61 eyes (77%). Of the 10 eyes (12%) that lost two or more Snellen lines of spectacle-cor rected or glare visual acuity, two had visual acuity of worse than 20/ 25. Central subepithelial corneal haze was absent to mild in 77 (96%) eyes at 12 months. CONCLUSIONS: Excimer laser photorefractive keratect omy as performed in this study was generally effective and safe in red ucing simple spherical myopia. Further studies of the effect of a larg er diameter ablation zone, smoother transitional corneal contours, and the effect of postoperative topical corticosteroids may lead to furth er improvements in outcome.