Visual outcomes after three different surgical procedures for correction of refractive error in patients with thin corneas

AIM: To investigate and compare the visual and refractive outcomes of small incision lenticule extraction ( SMILE), laser assisted sub-epithelial keratomileusis (LASEK), and LASEK combined with corneal collagen cross-linking (LASEK-CXL) surgery in patients with less than 500 mu m of central corneal thickness (CCT). METHODS: The retrospective medical records review was conducted on the patients with CCT less than 500 mu m treated with SMILE, LASEK, and LASEK-CXL. There was a total of 172 eyes, 76 eyes were in the SMILE group, 53 eyes in the LASEK group, and 43 eyes in the LASEK-CXL group. Uncorrected distance visual acuity (UDVA), spherical equivalent refraction (SE), and corneal haze were followed up in the three groups for 12mo. RESULTS: At 12mo postoperatively, there were no statistically significant differences in UDVA and in the absolute value of SE between the three groups. The predictability within +/- 0.50 D in the SMILE group (85.5%) was significantly higher than in both the LASEK group (64.2%, P<0.01) and the LASEK-CXL group (69.8%, P=0.04). The efficacy index and safety index were not significantly different among the three groups. Corneal haze at 12mo postoperatively was higher in the LASEK-CXL group (27.9%) than in the SMILE group (2.6%, P<0.01) and in the LASEK group (7.5%, P<0.01). CONCLUSION: In patients with CCT less than 500 mu m, SMILE, LASEK, and LASEK-CXL appear to be effective for myopic correction. Among them, SMILE surgery shows the highest predictability.