Comparison of Clinical Results between PRK and LASIK for Moderate Myopia

Lee, Jong Seok; Joo, Choun Ki

Abstract

Currently, although LASIK has proved to be effective for correcting the high myopia, it is increasingly being favored for correcting the moderate myopia. We compared the clinical results after excimer laser photorefractive keratectomy(PRK)and laser associated in situ keratomileusis(LASIK)for the correction of moderate myopia from -4.00 diopter to -6.25 diopter. 31patients(40 eyes)who underwent LASIK with microkeratome(SCMD, USA) and STAR laser(VISX, USA)and 29 patients(38 eyes)who underwent PRK with the same laser were examined retrospectively. Mean uncorrective visual acuity(UCVA)was 0.64+/-0.24 7 days after surgery which was 63%of that at postoperation 6 months in the PRK, while that was 0.73+/-0.21 7 days after surgery which was 85%of that at postoperation 6 months in the LASIK(p<0.05). However, at 2 and 6 months postoperatively, the mean UCVA was similar between two procedures(0.93+/-0.15, 0.96+/-0.14 for PRK and 0.85+/-0.22, 0.82+/-0.22 for LASIK, respectively (p>0.05)). At 7 days, the mean spherical equivalent for PRK was +1. 81+/-0.82 D, which was significantly more overcorrected than that for LASIK(+0.47+/-1.07 D(p<0.05)). In addition, the overall refractive regression from 7 days to 6 months was 1. 58D in the PRK compared with regression of 0.96D over the same period in the LASIK, while the mean refractive regression from 2 months to 6months was similar between two procedures(0.27 D for PRK and 0.39 D for LASIK). Cylindrical error within 1D was increased from 0.48 +/-0.36D before operation to 0.69+/-0.31 D of 6 months after operation in LASIK(p>0.05), whereas it was decreased from 0.39+/-0.31 D to 0.07+/-0.31D in PRK (p<0.05). Conclusively, although improvement in UCVA and mean spherical equivalent is more rapid in LASIK than in PRK, the increased propensity of cylindrical error and undercorrection in LASIK requires further investigation.