PURPOSE  To investigate the advantages and disadvantages of on-flap Epi-LASIK and off-flap Epi-LASIK.

METHODS A double-masked, randomized and prospective study was performed on 188 eyes of 94 patients. In each patient, after laser ablation, the epithelium sheet was repositioned in one eye (on-flap group) and was removed by a microsponge in the fellow eye (off-flap group). All the eyes had a therapeutic contact lens for about 2-4days. Patients were instructed to rate their pain and other uncomfortable symptoms on postoperative day 1, 2 and 3, haze formation, visual acuity and refraction were evaluated 1 month and 4 months postoperatively.

RESULTS Patients reported statistically signi?cant more pain on day 2 and 3 after surgery in the on-flap group. The mean epithelial healing time was statistically significant (P=0.018). On the postoperative day 7 (n=74), 77.03% of eyes had transparent corneas in the off-flap group and 41.41% in the on-flap group. The mean uncorrected visual acuity on postoperative day 7 was (1.08±0.38) in the on-flap group and was (1.17±0.35) in the off-flap group (n=74). It was statistically significant at 1 month postoperatively (n=51, P=0.000) and no significant difference at 4 months (P=0.485). On postoperative day 7, the haze was statistically significant (n=74,P=0.000), and it peaked the highest at 1 month postoperatively in the both groups, but had no significant difference at 1 month and 4 months postoperatively (P=0.392;P=0.229). In addition, at 1 month and 4 months, spherical equivalent was not statistically significant. The mean cylinder at 1 month after surgery was statistically significant(P=0.039).

CONCLUSIONS  The flap does not seem to reduce pain and speeding recovery time in early postoperative period, in comparison with on-flap group, off-flap group had less uncomfortable systom and had rapider epithelial recovery. In the late postoperative period, the outcomes suggest that on-flap and off-flap Epi-LASEK are safe and efficient procedures to correct low to moderate myopia.