Excimer laser photorefractive keratectomy using an erodible mask to treat myopic astigmatism.

PURPOSE: To evaluate the results of excimer laser photorefractive keratectomy (PRK) using an erodible mask to treat myopic astigmatism.

SETTING: Douglas Memorial Hospital Medical Centre, Fore Erie, Ontario, Canada.

METHODS: Photorefractive keratectomy was done on 25 consecutive eyes of 25 patients with myopic astigmatism using the OmniMed excimer laser and a compound single-use myopic erodible mask manufactured to produce a specific spherical and cylindrical correction for each individual patient. Follow-up ranged from 6 months for 25 patients to 1 year for 5 patients.

RESULTS: Six months after PRK, the mean preoperative sphere of -7.46 diopters (D) decreased to -0.17 D and the mean preoperative cylinder of 2.31 D dropped to 0.69 D; 73% of astigmatism was corrected. In the five eyes followed for 1 year, 94% of astigmatism was corrected. Correction of the myopic component was less predictable, with a wider than anticipated range of overcorrection.

CONCLUSIONS: Excimer laser PRK successfully corrected myopic astigmatism in patients with low and high myopia. The less predictable myopia results may have been secondary to increased procedure time, corneal dehydration, and difficulty in patient fixation and thus alignment.