Changes in posterior corneal elevation and effected factors after LASIK

Abstract

Objective To study changes in posterior corneal elevation after laser in situ keratomileusis (LASIK) and related factors.Methods It was a retrospective case series study.One hundred and two eyes of 51 myopic patients undergoing LASIK were examined with a Pentacam preoperatively,and 1 month and 3 months postoperatively.Analysis included posterior corneal elevation of the corneal apex,temporal superior,temporal inferior,nasal superior and nasal inferior quadrants (7 predetermined points in each quadrant) in a 4mm area of the central cornea.Results The changes in posterior corneal elevation in the corneal apex,temporal superior,temporal inferior,nasal superior and nasal inferior quadrants were-0.12±1.50 μm,0.18±1.70 μm,-0.16±1.50 μm,0.15±1.62 μm and 0.01±1.45μm,respectively,at 1 month,and were 0.58±1.49 μm,0.42±1.85 μm,-0.50±1.99 μm,0.59±1.67 μm and-0.36±1.70 μm,respectively,at 3 months.Between postoperative 1 month and 3 months,there was a significant difference in changes in the posterior elevation of the corneal apex,but there were no statistically significant differences in the 4 quadrants.At 1 month postoperatively,changes in the posterior corneal elevation in every area did not correlate with central corneal thickness (CCT),residual bed thickness (RBT),ablation depth (AD) or spherical equivalent (SE).At 3 months postoperatively,there was a significant positive correlation between changes in posterior elevation in the corneal apex and SE,but there was no significant correlation between changes in posterior corneal elevation in 4 quadrants and CCT,RBT,AD,SE.Conclusion LASIK surgery induces tiny changes in posterior corneal elevation in the central 4 mm area.Higher refractive errors may increase the trend of a forward shift of the posterior surface of the corneal apex. Key words: Keratomileusis,laser in situ; Keratectomy; Posterior corneal surface; Elevation; Myopia