Photorefractive Keratectomy as A Retreatment of Residual Myopia after Previous Laser in Situ Keratomileusis

Purpose: This study was planned to evaluate the efficacy, safety and complication of photorefractive keratectomy (PRK) as a retreatment of residual myopia after previous laser in situ keratomileusis (LASIK). Methods: In this descriptive study in ophthalmology ward, Feiz Hospital, Isfahan University of Medical Sciences, Iran, with the consideration of inclusion and exclusion criteria, 170 eyes of the 92 patients were selected and underwent PRK with mitomycin C. One hundred-twenty seven eyes were in the first group (myopia≤-2 diopter [D]) and 43 eyes were in the second group (myopia>-2 D). Results: This study was performed on 170 eyes of 92 patients with an average age of 35 years old (56 women and 36 men). The average interval between procedures was 17.5±3.2 months. After 1 year, 94.7% of the eyes had uncorrected visual acuity (UCVA) (20/40 or better) and 65.8% of eyes had UCVA (20/20 or better). 135 eyes (79.4%) were within ±0.5 D and 168 eyes (98.8%) were within ±1.00 D of target refraction. Two eyes lost one line of best corrected visual acuity (BCVA) and 14 eyes had BCVA gain. In this study 20 eyes presented with corneal haze after one year after PRK (11.8%). Five eyes (3.9%) in first group (myopia≤-2.0 D) developed corneal opacity from the patients in second group (myopia>-2.0 D) 15 cases (34.9%) encountered corneal opacity. Before and after PRK, spherical equivalents of eyes were -1.84±0.6 and -0.15±0.2 D respectively (P<0.001), mean UCVA was 0.34±0.23 and 0.92±0.14 of lines (P<0.001), mean BCVA was 0.94±0.4 and 0.98±0.5 of lines (P=0.84) and the mean corneal thickness was 428±20 and 407±12 microns respectively (P=0.032). Conclusion: PRK is an effective and safe procedure as a retreatment of post LASIK residual myopia. The treatment of higher grade of residual myopia has higher rate of postoperative