Femtosecond laser-assisted LASIK versus PRK for high myopia: comparison of 18-month visual acuity and quality.

Purpose: To compare 18-month outcomes between femtosecond laser-assisted LASIK (femto-LASIK) and photorefractive keratectomy with mitomycin-C (PRK-MMC) for myopia of more than 7.0 D in terms of visual acuity and quality.

Methods: In this comparative nonrandomized clinical trial, 60 eyes from 30 patients (30 eyes in each group) were enrolled. The two procedures were compared in terms of 18-month changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, ocular and corneal higher order aberrations (HOAs), and contrast sensitivity (CS).

Results: Mean myopia was -8.65 ± 1.51 and -8.04 ± 1.70 D (P = 0.149) and mean ablation depth was 109.37 ± 9.07 and 105.09 ± 12.59 µm (P = 0.138), in the femto-LASIK and PRK-MMC groups, respectively. Baseline parameters were not significantly different between the two groups (all P > 0.05). At 18 months postoperatively, 75 % in the femto-LASIK, versus 57.1 % in the PRK-MMC group, had 20/20 UDVA (P = 0.017). CDVA remained similarly unchanged in both groups (P = 0.616). No case had residual refractive error more than 1.0 D in the femto-LASIK group, while 33.5 % in the other group had more than 1.0 D residual error (P = 0.390). Changes in corneal HOA were not significantly different between the two groups (P = 0.260). Cases in the femto-LASIK group showed more increase in ocular HOA (P = 0.032) and coma (P = 0.083, power = 72 %). CS remained similarly unchanged in all spatial frequencies in both groups (all P > 0.05).

Conclusion: Although femto-LASIK induces more HOA compared to PRK-MMC, considering outcomes in terms of 20/20 UDVA, residual refractive error, and CS stability, femto-LASIK provides more favorable results than PRK-MMC in high myopia.