Abstract
Purpose: :
To better evaluate and compare the effect of the prophylactic use of two different concentrations and exposure times of mitomycin C (MMC) to inhibit haze formation after photorefractive keratectomy (PRK) for high myopia.
Methods: :
Forty eight eyes of twenty four patients, 10 men and 14 women, with high myopia were included in this prospective study. Mean age at the time of PRK plus MMC was 29.8 years. Before PRK, the mean spherical equivalent was –8.75 D (range, –7.00 to –11.25 D). In each patient, one eye was randomly assigned to PRK and a single intraoperative topical application of MMC and the fellow eye did not receive this treatment after PRK. The patients were divided into 4 groups: PRK plus MMC 0.02% for 2 minutes (Group 1), PRK plus MMC 0.02% for 30 seconds (Group 2), PRK plus MMC 0.002% for 2 minutes (Group 3), and PRK plus MMC 0.002% for 30 seconds (Group 4). The inclusion criteria were high myopia, no central corneal opacity and inadequate corneal thickness to allow a safe Laser in situ keratomileusis procedure. Refraction, uncorrected visual acuity, best spectacle corrected visual acuity (BSCVA), slit lamp evidence of corneal opacity (haze) and other visible complications, were evaluated over a mean 6–month follow–up period.
Results: :
Epithelial healing occurred between 3 and 5 days in all eyes. No adverse effects related to the use of MMC were observed during re–epithelialization or during follow up. Slit lamp grading showed a significant difference in haze formation between group 4 and groups 1, 2 and 3, and between group 1 and group 3. No significant difference was found between group 1 and group 2 or between group 2 and group 3. No eye from groups 1 and 2 lost any line of the BSCVA as compared to the pre–PRK values. Two eyes from group 4 and 1 eye from group 3 lost 1 line of the BSCVA. Mean final spherical equivalent achieved in the MMC treated eyes was: –0.25 ± 0.18 D in group 1, –0.36 ± 0.23 D in group 2, –0.55 ± 0.48 D in group 3, and –0.90 ± 1.30 D in group 4.
Conclusions: :
The prophylactic use of a single intraoperative topical application of mitomycin C produced lower haze rates, better UCVA and BCVA results. Although, corneal haze scores are inversely proportional to the concentration and exposure time of MMC.
Keywords: refractive surgery: PRK • refractive surgery: comparative studies • drug toxicity/drug effects