Longitudinal comparison of femtosecond-assisted sub-Bowman keratomileusis versus photorefractive keratectomy for high myopia.

Abstract

To longitudinally compare the visual and refractive outcomes and changes in corneal thickness between femtosecond-assisted sub-Bowmen keratomileusis (SBK) and photorefractive keratectomy (PRK) with mitomycin C in eyes with high myopia. Patients with spherical equivalent ≥6 dioptres (D) who underwent femtosecond-assisted SBK or PRK with mitomycin C were recruited. All patients were examined preoperatively and after 1 week, and, 1, 3, 6 and 12 months postoperatively. Assessments included uncorrected and best-corrected distance visual acuity , and manifest refraction spherical equivalent. Corneal thickness was measured using swept source optical coherence tomography. A total of 110 eyes were included (68 PRK, 42 SBK). Change in efficacy index and safety index was not significantly different between both groups beyond 1 week postoperatively (p≥0.116). Manifest refraction spherical equivalent changed significantly from -9.02±1.92 D preoperatively to -0.21±0.31 D and from -8.25±1.10 D preoperatively to -0.53±0.55 D at 1 year after PRK and SBK, respectively (p<0.0001). The variance of postoperative refraction was significantly smaller after PRK throughout the 1-year follow-up compared with SBK (p≤0.0024). The central corneal thickness stabilised at 1 week after PRK and 3 months after SBK. Our study showed that femtosecond-assisted SBK and PRK with mitomycin C have comparable safety and efficacy for correction of high myopia. However, better predictability of postoperative refraction was noted after PRK compared with SBK.