AIM: To compare the changes in epithelial thickness profile following TransPRK and Epi-LASIK for myopia.

METHODS: In this prospective non-randomized controlled study, 76 right eyes of 76 myopic patients with the spherical equivalent refraction -1.25 to -6.00D were included under the informed consent. The eyes were divided into TransPRK group for 43 eyes and Epi-LASIK group for 33 eyes. Epithelial thickness was measured using spectral-domain optical coherence tomography at different corneal zones(central, 2mm; paracentral, 2-5mm; and mid-peripheral, 5-6mm)preoperatively and at 1, 3, and 6mo postoperatively. The results were compared between the two groups.

RESULTS: The epithelium were thicker at 3 and 6mo after surgery compared to preoperative measurements in the two groups(all P<0.05). In TransPRK group, the epithelial thickness at 3 and 6mo demonstrated a negative meniscus-like lenticular pattern with lesser thickening centrally and progressively great thickening centrifugally(F_3mo=-2.687,P=0.027; F_6mo=-2.908,P=0.000). No statistically significant change was detected among the three zones in Epi-LASIK group(F=1.365, P=0.237). The epithelial thickness was thicker in the TransPRK group compared to the Epi-LASIK group mid-peripherally(P<0.05).

CONCLUSION: Significant epithelial thickening was observed after TransPRK and Epi-LASIK. It was showed a lenticular change with more thickening mid-peripherally after TransPRK than Epi-LASIK. Wound healing and inflammation may account for differences in the effect on epithelial thickness change by both surgeries.