AIM: To investigate the efficacy and safety of low dose mitomycin C(MMC)to prevent haze in trans photorefractive keratectomy(TransPRK)with moderate and high myopia, and to observe the changes of corneal density.

METHODS: Sixty-one patients underwent TransPRK with moderate and high myopia. Eyes were divided into research group(0.1g/L MMC for 40s)and control group(0.2g/L MMC for 40s)randomly. There were 21 patients in research group and 40 patients in control group. Cornea epithelial healing time, pain score, visual acuity, manifest refraction, haze and cornea density were analyzed.

RESULTS: The epithelial healing time(0.1g/L group: 3.86±1.11d, 0.2g/L group: 4.23±1.27d)and pain score(0.1g/L group: 2.01±0.58, 0.2g/L group: 1.79±0.7)were no significant difference between two groups(P=0.667, P=0.582). It was similar in spherical equivalent at 1mo and 3mo post-operation(0.1g/L group: 0.28±0.25, 0.05±0.23D; 0.2g/L group: -0.13±0.17, 0.07±0.22D; P=0.178, P=0.490). The BCVA of control group decreased at 1mo and improved to the same level as pre-operation at 3mo(F=15.847, P<0.001); 0.1g/L group showed the same trend, but the changes were no significant difference(F=3.038, P=0.093). There were also no significant difference in Haze between two groups post-operation(z=-0.709, P=0.479; z=-0.478, P=0.633).The change of cornea density was matched with the BCVA(0.1g/L group F=27.399, P=0.001; 0.2g/L group F=8.313, P=0.001)and it was similar between two groups.

CONCLUSION: The using of low dose MMC to prevent haze in TransPRK with moderate and high myopia is safe and effective. It is therapeutic equivalence to regular dose(0.2g/L). Besides the slit lamp, we can use the corneal density to measure the corneal transparency.