Comparison of clinical outcomes after femtosecond laser in situ keratomileusis in eyes with low or high myopia

AIM: To compare the clinical results of femtosecond(FS) laser in situ keratomileusis(LASIK) in high myopic patients and low myopic patients.METHODS: This study included 212 myopic eyes undergoing LASIK using a VisuMax 500 kHz FS laser. All treated eyes were assigned to one of two groups according to preoperative manifest spherical refraction: low myopia group(A, >-4.0 D) and high myopia group(B, ≤-4.0 D). Uncorrected and corrected distance visual acuity(UDVA, CDVA), refractive errors, and higher-order aberrations(HOAs) were measured preoperatively and 1 wk, 1, 3 and 6 mo postoperatively.RESULTS: At 6 mo of follow-up, 92% and 76% had a UDVA of 20/20 or better in group A and B, respectively(P=0.037) and UDVA was significantly different between two groups(P=0.042). Six and seven percentage lost one line of CDVA in group A and B, respectively(P=0.572) and no eyes in both groups lost more than two lines. Each group had 87% and 76% of treated eyes within ±0.5 D of the intended correction(P=0.186), and 13% and 43% with a change of >0.50 D in spherical equivalent from 1 wk to 6 mo postoperatively(P=0.005). In terms of postoperative astigmatism, each group had 89.1% and 76.6% within ±0.50 D, respectively and there was significant difference(P=0.006). Group A tends to induce smaller HOAs than group B.CONCLUSION: FS LASIK is effective and safe for correcting high myopia as well as low myopia. However, high myopic eyes showed more postoperative astigmatism and HOAs which affect visual acuity.