Clinical research of changes in posterior corneal elevation after small incision lenticule extraction

Abstract

AIM:To assess the changes of posterior corneal elevation after small incision lenticule extraction(SMILE). METHODS:A retrospective study was conducted on 120 patients(240 eyes)who underwent SMILE surgery with myopia. All patients were examined with the Pentacam of preoperation and 1d, 1wk, 1, 3, 6 and 12mo postoperatively, respectively. We analyze the change of the posterior corneal elevation of the apex, and the change of mean posterior corneal elevation in the circle of 2mm, and 6mm diameter.RESULTS:Comparison among the three groups showed that the differences of apex and 2mm circle at a different time and between the groups were statistically significant(apex: Ftime=30.09, Ptime<0.01; Fgroup=7.29, Pgroup<0.01; 2mm circle: Ftime=24.72, Ptime<0.01; Fgroup=7.44, Pgroup=0.01), and there was no statistically significant difference in interaction time and groups(apex: Ftime×group=1.65, Ptime×group=0.15; 2mm circle: Ftime×group=1.81, Ptime×group=0.25). The difference of 6mm circle at different time points after the operation was statistically significant(Ftime=18.34, Ptime<0.01), while the difference in interaction time and groups was not statistically significant(Fgroup=2.21, Pgroup=0.12; Ftime×group=1.34, Ptime×group=0.25). In the low and moderate myopia groups, the changes of the apex, 2mm circle and 6mm circle in the posterior corneal elevation were statistically significant within 1mo after surgery(P<0.05); In the high myopia group, there were statistically significant at the apex and 2mm circle within 3mo after surgery(P<0.05); There was statistically significant after surgery at 6mm circle within 1mo(P<0.05). In all cases, the difference of the posterior corneal elevation between 1wk and 1d was negative at the apex and 2mm circle, after that, the difference became positive and smaller. The reverse was true at the 6mm circle. CONCLUSION:Among three groups after SMILE, the central posterior cornea was slightly backward, and the peripheral cornea was slightly forward, the changes were most obvious after 1wk and then returned gradually. It means the surgery was safe, stable, precise, and predictable.

Keywords

• small incision lenticule extraction
• posterior corneal elevation
• corneal stroma
• myopia