Change of Posterior Corneal Surface after Laser In Situ Keratomileusis; One Year Fallow-up

ABSTRACT

PURPOSE: To investigate the change of the posterior corneal surface for 1 year after LASIK METHODS: Ninety-nine eyes of 57 patients who underwent LASIK were evaluated retrospectively. The posterior corneal surface was evaluated before surgery and at 1 week, 2 months, 6 months and 1 year postoperatively. The patients were divided into two groups based on the preoperative mean spherical equivalent (Group I; -2.5 ~ -6.0 D, Group II; -6 ~ -10 D) and two groups based on the residual bed thickness (RBT Group A; 250 ~ 300 micrometer, Group B; 300 ~ 350 micrometer). We also grouped them based on the ablation percentage of the total corneal thickness (P/TCT Group 1; below 10%, Group 2; 10-15%, Group 3; 15-20%) RESULTS: The posterior corneal surface in Group I was shifted forward 14.19 +/- 8.98 micrometer at 1 week, 7.93 +/- 5.64 micrometer at 1 year after LASIK, and 19.77 +/- 6.97 micrometer and 14.93 +/- 6.95 micrometer in Group II, respectively. It was displayed forward shift 19.48 +/- 8.54 micrometer at 1 week and 13.04 +/- 7.14 micrometer at 1 year in Group A and 11.64 +/- 6.09 micrometer and 7.07 +/- 5.26 micrometer in Group B, respectively. The values at the same times were 8.49 +/- 5.83 micrometer and 5.45 +/- 4.18 micrometer in Group 1, 17.21 +/- 7.73 micrometer and 9.12 +/- 5.26 micrometer in Group 2 and 20.25 +/- 8.16 micrometer and 16.05 +/- 7.24 micrometer in Group 3, respectively. CONCLUSIONS: The posterior corneal surface shifted forward early time after LASIK, but showed a trend toward gradual backward shifted over time. The eyes with higher myopia, thinner RBT and higher P/TCT were more shifted forward the posterior corneal surface at l year after LASIK.