Seven-year observation of posterior corneal elevation after small-incision lenticule extraction in patients with moderate and high myopia.

ABSTRACT

PURPOSE: To investigate the long-term changes in posterior corneal elevation in moderate and high myopia after small-incision lenticule extraction (SMILE). SETTING: Eye & ENT Hospital, Fudan University, Shanghai, China. DESIGN: Prospective case series. METHODS: 33 eyes of 20 patients (30.1 ± 9.5 years, 7 men and 13 women, spherical equivalent [SE] range -4.00 to -8.75 D, mean SE -6.25 ± 1.29 D) who underwent SMILE were included. Changes in the posterior corneal elevation at central points (PCE), the thinnest point (PTE), the maximal point (PME), and an additional 20 points within the 4 mm area of the best-fit sphere were evaluated with a Pentacam (Oculus Optikgeräte GmbH) during a 7-year follow-up period. Mixed linear models were used to evaluate changes with P values less than 0.05. Correlations of elevation changes and residual bed thickness (RBT) were also evaluated. RESULTS: No ectasia was observed among the 33 eyes studied. The safety index was 1.08, and the efficacy index was 1.03. The mean change in PCE at 1 year, 3 years, 5 years, and 7 years was -1.42 ± 0.95 µm, -2.67 ± 0.98 µm, -2.44 ± 1.06 µm, and -1.91 ± 0.92 µm, respectively. Statistically significant differences were found at 3 years, 5 years, and 7 years (P = .007, .023, and .040, respectively). PTE reduced significantly at each time point compared with baseline. The mean change was -2.82 ± 1.19 µm, -3.55 ± 1.22 µm, -3.47 ± 1.32 µm, and -2.39 ± 1.15 µm, respectively (P = .019, .004, .010, and .039, respectively). PME changed in 2.45 ± 1.02 µm at 7 years compared with baseline (P = .017). The changes in PCE and PME negatively correlated with the RBT. CONCLUSIONS: Long-term posterior corneal elevation was stable in moderate and high myopia after SMILE.