Change in central corneal thickness following laser in situ keratomileusis for myopia.

Central corneal thickness alterations may cause residual refractive errors following laser in situ keratomileusis (LASIK). This study reports associations between central corneal thickness alterations and residual refractive error following uncomplicated LASIK. Ninety-one myopic patients with a mean refractive correction of -3.91+/-3.2 DS / -0.66+/-0.3 DC were evaluated. Central corneal thickness was measured prior to, during and following surgery and 2 months later using ultrasound pachometry Results indicate increased tissue removal (94+/-33 microm; mean +/- SD) compared to the nominal Nidek value (52+/-24 microm, P<0.001). Twenty-four hours later the tissue removal was 46+/-27 microm. There was no association between altered central corneal thickness and ablation depth (r = 0.058, P = 0.454). Central corneal thickness change was inversely proportional to residual refractive error (r = -0.364, P<0.01). Increased tissue removal may occur due to rapid stromal dehydration. Central corneal thickness changes between 24 h, and 2 months after surgery were constant over a range of ablation depths, which may partly explain the stability of LASIK procedures over a range of corrections.