AIM:To compare transforming growth factor-β1 (TGF-β1) levels in tears and the degree of corneal haze formation following epithelial laser in situ keratomileusis (Epi-LASIK) with and without the use of mitomycin C (MMC) and to investigate the effect of MMC on corneal wound healing.METHODS:Thirty-two patients (64 eyes) with high myopia underwent Epi-LASIK surgery, and MMC was randomly used in one eye in each patient. The epithelialization process was observed, and the TGF-β1 level in tears was measured at 1 day, 3, and 7 days postoperatively for comparison with baseline. Corneal haze was graded at 1 month, 3, and 6 months after surgery.RESULTS:Mean preoperative spherical equivalent refraction was -8.24±2.18D (range -6.00 to -10.50D) in the MMC group and -7.82±1.55D (range -6.00 to -9.75D) in the non-MMC group. There was no significant difference between the two groups (P=0.38). Mean epithelialization time was (5.02±0.68) days in the MMC group and (4.86±0.57) days in the non-MMC group (P=0.31). Tear fluid TGF-β1 levels were similar before surgery (P=0.34), but were significantly higher in the non-MMC group at 1 day, 3, and 7 days postoperatively (P=0.004, 0.008, and 0.012, respectively). Corneal haze scores 1 month after surgery were significantly higher in the non-MMC group (P=0.03), and similar at 3 and 6 months after surgery (P=0.28 and 0.62, respectively).CONCLUSION:MMC did not delay epithelialization. In early postoperative period, lower TGF-β1 levels in tears and a lower grade of corneal haze were observed in the MMC group. Our findings suggest that the ability of MMC to inhibit Epi-LASIK-induced haze might be mediated through TGF-β1 suppression.