Intraocular straylight and corneal morphology six months after LASIK

To assess the relationship between changes in human corneal morphology and intraocular straylight produced over time after laser in situ keratomileusis (LASIK).

Thirty subjects who underwent LASIK surgery were enrolled in this single-center, prospective and longitudinal trial. Twenty-five eyes were included in the study. A scanning, slit white light confocal microscope using a ConfoScan 4 equipped with 40x front lenses and a sensor called "z-ring" was used to examine structural changes in a cornea. Endothelial and stromal cellular count was randomized and masked at observer. Straylight was determined using the van den Berg straylight meter (third generation). All measurements were obtained over time and compared.

No significant differences were detected in the endothelial layer. Anterior keratocyte density was lower at the time points of 15 days and 6 months after refractive surgery (p < 0.01, analysis of variance) than the presurgery value, although densities at 6 months failed to differ with Wilcoxon matched-pairs signed rank test. Posterior keratocyte density was reduced at 15 days post-surgery but had recovered slightly at 6 months (p < 0.05) with analysis of variance and Wilcoxon matched-pairs signed rank test. Intraocular straylight measurements improved after surgery with significant differences observed when presurgery values were compared to those recorded 15 days or 6 months after LASIK (p < 0.01) with analysis of variance being adjusted by the Kruskal-Wallis test. However, straylight value at 6 months failed to differ with Wilcoxon matched-pairs signed rank test. Correlation was detected between diminished anterior keratocyte density and increased intraocular straylight both at 15 days (r = -0.50, p < 0.05) and 6 months (r = -0.53, p < 0.05).

Patients with anterior corneal cell density reduced as a consequence of LASIK, showed augmented intraocular straylight. This correlation warrants further research with larger samples.