Corneal flattening following collagen crosslinking for keratoconus: Findings at 5-year follow-up

Abstract

Purpose: To study the corneal flattening effect of cross-linking (CXL) overtime and to look for a potential association with preoperative topographic variables and the central depth of demarcation line (DDL). Methods: 201 eyes of 146 patients (mean age of 31.2 ± 7.3 years) with progressive keratoconus who underwent CXL between June 2007 and December 2012 were enrolled in this retrospective study. Follow-up visits were performed at different time intervals for at least 5 years. Preoperative parameters and depth of demarcation line were collected from LaserVision ophthalmology center in Lebanon. Corneal flattening was defined by a change in postoperative Kmax (ΔKmax) greater than 1.00 D. Results: ΔKmax increased from 50.25% to 61.69%, from first to last follow-up visits. The only factor significantly correlated to ΔKmax during all follow-up visits was preoperative maximum keratometry (Kmax) especially when greater than 50.00 D (OR, 1.92; 95% CI, 1.10–3.34). All eyes showed a corneal demarcation line (mean central depth (DDL): 217.11 ± 26.54 μm), with no statistically significant correlation between DDL and ΔKmax. Conclusion: CXL effect on cornea can be cumulative overtime and delayed flattening occurs in some cases. ΔKmax is positively correlated with preoperative Kmax and no association was found between ΔKmax and DDL. Therefore, DDL may not be a valid measure for the efficacy of CXL.

Tomographic changes after corneal collagen cross-linking for progressive keratoconus - one-year follow-up study

“…However, due to the natural changes in tomographic indices after CXL, there is still no clear consensus for definition of KC progression after CXL. Corneal thinning has been observed in cross-linked corneas in our and similar studies [15]. We also observed significant decrease of corneal thickness in both spots, maximum posterior elevation height and thinnest corneal point, during one-year follow-up.…”

“…Natural course of topographic changes after CXL is important for proper visual rehabilitation. Better spectacle correction and contact lens tolerance following CXL was observed in our and similar studies [13,14,15]. In addition, it is of particular interest to evaluate treatment response after CXL at different time points.…”