Photorefractive Keratectomy for Residual Myopia after Myopic Laser in Situ Keratomileusis

Abstract

Purpose. To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) on the corneal flap for correction of residual myopia following myopic laser in situ keratomileusis (LASIK). Patients and Methods. A retrospective study on eyes retreated by PRK on the corneal flap for residual myopia after LASIK. All eyes had no enough stroma after LASIK sufficient for LASIK enhancement. Data included spherical equivalent (SE), uncorrected and best corrected visual acuity (UCVA and BCVA), central pachymetry, corneal higher order aberrations (HOAs), corneal hysteresis (CH), corneal resistance factor (CRF), and corneal haze. Results. The study included 64 eyes. Before PRK, the mean central pachymetry was 400.21±7.8 μm, the mean SE was-1.74±0.51 D, and the mean UCVA and BCVA were 0.35±0.18 and 0.91±0.07, respectively. 12 months postoperatively, the mean central corneal thickness was 382.41±2.61 μm, the mean SE was-0.18±0.32 D (P<0.01), and the mean UCVA and BCVA were 0.78±0.14 (P=0.01) and 0.92±0.13 (P>0.5), respectively. The safety index was 1.01 and the efficacy index was 0.86. No significant change was observed in corneal HOAs. Conclusions. Residual myopia less than 3 D after LASIK could be safely and effectively treated by PRK and mitomycin C with a high predictability. This prevents postoperative ectasia and avoids the flap related complications but has no significant effect on HOAs.