Evaluating corneal changes after corneal collagen cross-linking in keratoconus by optical coherence tomography

Abstract

Purpose The aim of this study was to evaluate the corneal changes after corneal collagen cross-linking (CXL) in progressive keratoconus using anterior segment optical coherence tomography. Patients and methods This prospective interventional noncomparative case-series study was conducted on 30 eyes of 18 patients of both sexes with a mean age of 23.11±4.06 years diagnosed as progressive keratoconus patients with clear central cornea. All eyes underwent epithelium-off accelerated CXL. Anterior segment optical coherence tomography and Scheimpflug camera imaging were done to all cases preoperatively and at 1, 3, and 6 months, postoperatively. Results The demarcation line (DL) was detected in all eyes 1 month postoperatively, and was still detected at 3 and 6 months, postoperatively. However, it was accurately measured until 3 months postoperatively. At 6 months, it was barely visible, so measuring its depth was difficult to be done. There was a statistically significant positive correlation between the thinnest corneal thickness and the central corneal DL depth (r=0.480, P=0.006). There was no statistically significant correlation between the maximum keratometric reading (K-max) and the depth of central corneal DL (r=−0.253, P=0.17). In addition, there was no statistically significant correlation between corneal densitometry and the depth of central corneal DL (r=−0.68, P=0.715). Conclusions The DL is a direct clinical sign of corneal CXL and can be found within 6 months after the treatment, being most clearly visible at 1 month after CXL. However, the line starts to be less visible after 3 months and becomes barely visible after 6 months postoperatively, making it difficult to measure its depth at that time.