Two-step versus single application of mitomycin-C in photorefractive keratectomy for high myopia

Purpose: To evaluate the long-term outcomes of two-step versus single application of mitomycin-C [MMC] during photorefractive keratectomy [PRK] for high myopia

Methods: This randomized clinical trial included consecutive patients with high myopia [exceeding 7 D]. Patients underwent PRK and were randomized to two methods of MMC 0.02% application as follows: in the single application group, MMC was applied for 45 seconds followed by irrigation; in the two-step group MMC was used identically followed by repeat application for another 15 seconds and corneal surface irrigation. Visual acuity, refractive error, pachymetry, topography, corneal haze and complications were compared between the two groups 18 months after surgery

Results: One hundred and forty patients [70 subjects in either study arm] underwent PRK according to the study protocol. Mean spherical equivalent refractive error was significantly reduced from baseline to-1.16 +/- 0.39 D in the single application group and to-1.07 +/- 0.39 D in the two-step group. Sixteen [11.5%] versus 8 [5.7%] eyes lost one or more line[s] of best corrected visual acuity in the single application group as compared to the two-step group [P=0.05]. Corneal haze was observed in 18 [12.9%] and 8 [5.7%] eyes in the single application versus two-step group, respectively [P=0.04]. Grade 3 corneal haze was not observed in the two-step group but occurred in five eyes [3.6%] in the single application group [P=0.03]. No eyes developed corneal ectasia during the follow-up period. Two-step intraoperative application of MMC 0.02% in highly myopic eyes undergoing PRK can reduce the frequency and severity of haze formation

Results of photorefractive keratectomy with mitomycin C for high myopia after 4 years

This study assessed the long-term results of photorefractive keratectomy [PRK] with mitomycin C in high myopia [>/= 7 diopter]. In this retrospective study, visual acuity, refractive error, pachymetry, topography, contrast sensitivity, corneal haze safety, predictability and complications [with emphasis on ectasia] of 37 high myopic patients [72 eyes] who had PRK surgery with mitomycin C in the last 10 to 40 months were assessed. The exclusion criteria included previous ocular surgery other than LASIK, current ocular disease and any systemic illness. The mean follow up period was 27.2 +/- 7.9 months. The spherical equivalent error was significantly reduced, from a mean of-9.10 +/- 2.12 diopters [D] [range of-7 to -18.25 D] before PRK to a mean of-1.81 +/- 1.57 D [range of-8.5 to 0 D] after [P = 0.001]. Postoperatively, 34.72% of eyes were within +/- 0.5 D of attempted correction and 58.33% within +/- 1 D and 84.72% within +/- 2 D. 80.5% of eyes had a vision of 20/40 or better. Best corrected visual acuity [BCVA] was unchanged or improved in 93.05%. The safety index was 0.96 [the ratio of mean postoperative BCVA [0.84] to mean preoperative BCVA [0.87]] and efficacy index was 0.8 [the ratio of mean postoperative unconnected visual acuity [0.7] to mean preoperative BCVA [0.87]]. Corneal haze formation was seen in 5 patients [6.9%] with grade +1. The minimum stromal residual bed was 400 micro m. No eyes had progressive corneal ectasias at the time of post-op control. The topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK. Predictability of refractive results, however, was poor