The correction of high myopia using the excimer laser
J. Heitzmann, P. S. Binder, B. S. Kassar and L. T. Nordan
Mericos Eye Institute, Scripps Memorial Hospital, La Jolla, Calif.
OBJECTIVE: 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).
DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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.
