The correction of high myopia using the excimer laser

To determine the safety and efficacy of excimer laser photoablation as a treatment to correct high myopia that is defined as a spherical equivalent refractive error greater than -8.00 diopters (D).

Using a multizone (4.0-, 5.0-, and 6.0-mm) photorefractive keratectomy 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 ranged from -8.00 to -19.50 D (mean +/- SD, -11.83 +/- 2.92 D); the mean attempted ablation depth was 93.0 +/- 20.2 microns.

At the last postoperative examination (mean +/- SD, 7.5 +/- 3.7 months), the mean +/- SD spherical 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 corrected acuity, whereas two eyes lost 2 Snellen lines; 39% of the eyes were +/- 1.00 D; and 65% were +/- 2.00 D of attempted correction. Corneal haze (corneal clarity score of > or = 1.5) was observed in 47% of the eyes at some time postoperatively.

Photorefractive keratectomy for high myopia was found to be not nearly as efficient or predictable as it is for low myopia. A greater incidence 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 keratectomy for myopia that is greater than 8.00 D does not appear to prevent subsequent haze or refractive regression.