THE CORRECTION OF HIGH MYOPIA USING THE EXCIMER-LASER

Objective: To determine the safety and efficacy of excimer laser photo ablation as a treatment to correct high myopia that is defined as a sp herical equivalent refractive error greater than -8.00 diopters (D). D esign: Using a multizone (4.0-, 5.0-, and 6.0-mm) photorefractive kera tectomy protocol for correction of high myopia, 23 eyes in 18 patients were treated at one clinical center with an excimer laser (VISX Inc, Santa Clara, Calif). Preoperative spherical equivalent refractions ran ged from -8.00 to -19.50 D (mean+/-SD, -11.83+/-2.92 D); the mean atte mpted ablation depth was 93.0+/-20.2 mu m. Results: At the last postop erative examination (mean+/-SD, 7.5+/-3.7 months), the mean+/-SD spher ical equivalent refraction was -1.09+/-2.08 D, including results from two repeated procedures; visual acuity in 52% of the eyes was 20/40 or better uncorrected; 65% of the eyes improved or did not change best c orrected acuity, whereas two eyes lost 2 Snellen lines; 39% of the eye s were +/-1.00 D; and 65% were +/-2.00 D of attempted correction. Corn eal haze (corneal clarity score of greater than or equal to 1.5) was o bserved in 47% of the eyes at some time postoperatively. Conclusions: Photorefractive keratectomy for high myopia was found to be not nearly as efficient or predictable as it is for low myopia. A greater incide nce of regression of refractive effect and corneal haze were noted in these cases compared with reported studies of low to moderate myopia. A multizone approach to reduce ablation depth during photorefractive k eratectomy for myopia that is greater than 8.00 D does not appear to p revent subsequent haze or refractive regression.