Changes in central corneal thickness and refractive error after thin-flap laser in situ keratomileusis in Chinese eyes

Abstract

Background: Refractive stability is influenced by alterations in corneal curvature and corneal thickness after laser in situ keratomileusis (LASIK). The aim of this study was to analyze the changes of central corneal thickness (CCT) and refractive error following thin-flap LASIK surgery in Chinese eyes.

Methods: One hundred and fifty-eight myopic patients (302 eyes) who underwent thin-flap LASIK surgery were prospectively evaluated. CCT was measured by non-contact specular microscopy before, and 1 day, 1 week, and 1, 3, and 6 months following surgery. Age, refractive error, and optic zone diameter were also recorded.

Results: Preoperatively, the mean CCT was 531.6 ± 24.3 μm. At 1 day, 1 week, and 1, 3, and 6 months after surgery, mean CCTs were 431.4 ± 38.4 μm, 422.6 ± 3 7.8 μm, 427.2 ± 38.0 μm, 434.4 ± 38.2 μm, and 435.6 ± 38.0 μm, respectively. Significant changes were detected in CCT values at each time point after thin-flap LASIK treatment (P < 0.05). The mean preoperative spherical equivalent (SE) was -5.73 ± 2.30 diopters (D). At 1 day, 1 week, and 1, 3, and 6 months after surgery, it was 0.26 ± 0.58 D, 0.54 ± 0.52 D, 0.49 ± 0.53 D, 0.45 ± 0.49 D, and 0.37 ± 0.42 D, respectively. The spherical equivalent refraction at 6 months postsurgery was close to the predicted value (0.34 ± 0.30 D). The changes in CCT within 6 months (4.06 ± 9.99 μm) were negatively correlated with age, preoperative refractive error, and optical zone diameter, respectively (r = -0.180, P < 0.05; r = -0.187, P < 0.001; r = -0.171, P < 0.05, respectively). No significant correlation was found between CCT changes and SE changes at different time points, postoperatively.

Conclusions: CCTs decreased significantly at 1 day after surgery, and continued to decline at 1 week after surgery, then increased over time. From postoperative 1 week, SE over time continually shifted to the myopic side.

Fig. 1

CCT values in pre-surgery, 1 day, 1 week, and 1, 3, and 6 months postsurgery. Central corneal thickness (CCT, in μm) decreased significantly at 1 day (D) after surgery, and continued to decline at 1 week (W). Then it began to increase over time to 6 months (M). Pre-op = preoperative; Post = postoperative. Error bars indicate mean ± SD

Fig. 2

Changes of spherical equivalents (in diopters, D) for up to 6 months after surgery. From 1 week (W) postsurgery, there was a myopic shift over time to 6 months (M). Pre-op = preoperative; Post = postoperative. Error bars indicate mean ± SD