Abstract
Purpose: :
Topical mitomycin C (MMC) (0.02%) after photorefractive keratectomy (PRK) has been clinically tested at various exposure times. We have taken on a different approach by reducing its concentration 10 fold (0.002%), and compare its effectiveness to PRK without topical MMC.
Methods: :
The efficacy of 100 eyes receiving PRK without MMC is sequentially compared to a similar number of those receiving a low dose exposure (0.002%). The topical exposure times for MMC depended on the level of myopia, and was 45 sec for –3 to –6 D (group 1), 90 sec for –6 to –9 D (group 2) and 2 min for >–9 D (group 3). The patients were examined pre and postoperatively at 1 wk, 1 mo, 2 mo, 3 mo, 6 mo, 1 yr, and 2 yrs. Statistical analysis of haze and visual acuity was analyzed by analysis of variance (ANOVA), and was considered statistically significant for a p value <0.05. Haze level was graded as 0.5, 1+, 2+, 3+ or 4+ according to Fantes scale.
Results: :
The preoperative findings in each of the three groups was statistically similar between low dose MMC and the control. Haze levels were significantly less in the low dose vs. no MMC eyes in each group at each postoperative time point {ie. mean haze in Group 1: 0.52 vs 1.00 at 1 mo (p<1.8E–16), 0.044 vs 0.84 at 6 mo (p <9.2E–11), 0.049 vs 0.58 at 2 years (p<2.9E–7); Group 2: 0.50 vs 1.10 at 1 mo (p<4.8E–19), 0.28 vs 0.89 at 6 mo (p<6.4E–11), 0.29 vs 0.82 at 2 years (p<3.2E–6); and in Group 3: 0.53 vs 1.12 at 1 mo (p<1.2E–18), 0.32 vs 1.58 at 6 mo (p<3.9E–17), 0.39 vs 1.24 at 2 years (p<1.5E–12)}. Overall mean UCVA was also statistically better in the low dose MMC eyes at 1 mo: 0.82 vs 0.71 (p=0.011), 1 year: 0.84 vs 0.75 (p=0.032) and 2 years: 0.82 vs 0.69 (p=0.014).
Conclusions: :
Low dose topical MMC (0.002%) after PRK induces less corneal haze than eyes not receiving this cytotoxic agent. Concerns of safety with MMC makes the efficacious use of a 10 fold less concentration more desireable. Although the mean level of haze without MMC tended to diminish slightly with time, it was still statistically worse at 1 and 2 years and with worse visual acuity. Further comparative studies of low dose vs. higher dose MMC with shorter exposures are recommended to fully characterize its clinical benefit.
Keywords: refractive surgery: PRK • refractive surgery: comparative studies • drug toxicity/drug effects