Long-term stability of the posterior cornea after laser in situ keratomileusis

PURPOSE: To study long-term changes in posterior corneal elevation after laser in situ keratomileusis (LASIK) using Scheimpflug topography (Pentacam, Oculus, Inc.) in eyes 1 year after LASIK. SETTING: Department of Ophthalmology, Albany Medical Center, and a private practice, Albany, New York, USA. METHODS: One hundred two myopic eyes of 52 consecutive patients presenting for their 1-year follow-up were prospectively evaluated using the Pentacam to determine elevation changes to the posterior corneal surface between preoperative and 1-year postoperative measurements. Changes in posterior elevation were performed by comparing the best-fit sphere preoperatively and postoperatively with a fixed reference sphere determined by the central 9.0 mm preoperative cornea. Statistical and graphical analyses were performed. RESULTS: One hundred two post-LASIK eyes (mean correction -4.33 diopters; mean ablation depth 68.70 mu m; mean estimated residual bed thickness 327 mu m had a mean posterior displacement of -0.47 mu m +/- 3.48 (SD) (range -10.0 to +7 mu m). The mean follow-up period was 13.6 months (range 8.8 to 19.3 months). CONCLUSIONS: In this population, no patient had significant forward protrusion of the posterior corneal surface a mean of 14 months after LASIK. The posterior cornea in post-LASIK myopic eyes was very stable. Contrary to results in previous studies, progressive changes to the posterior corneal surface did not routinely occur after LASIK performed within established parameters.