Corneal Collagen Cross-Linking

Abstract

To review outcomes of corneal collagen cross-linking (CXL) for keratoconus (KC) or ectasia in a cornea subspecialty practice. Results from controlled clinical trials at a single site cornea subspecialty practice, including 104 eyes (66 KC and 38 ectasia). Outcomes and the natural course of changes in postoperative parameters including maximum keratometry (KMax), uncorrected visual acuity (UCVA), and best-corrected visual acuity (BCVA) over 12 months are reviewed. In addition, corneal topography indices, wavefront higher-order aberrations, and the natural history of wound healing after CXL are discussed. Characteristics associated with CXL outcomes are reviewed as well. In predicting treatment outcomes for KMax and BCVA, the preoperative patient characteristics examined were gender, age, disease group, cone location, thinnest pachymetry, UCVA, BCVA, and KMax. At 1 year, an average of 1.7 diopter (D) flattening in KMax was found. Mean BCVA improved slightly more than 1 line (from 0.35±0.24 to 0.23±0.21 logMAR). All postoperative parameters similarly follow a trend of worsening between baseline and 1 month, and improvement thereafter. More specifically, quantitative improvements are typically seen at 3 months and may continue between 3 and 12 months. A review of baseline patient characteristics indicated that (1) eyes with preoperative KMax of 55 D or steeper were 5.4 times more likely to gain 2 D or more of KMax flattening at 1 year after CXL, and (2) eyes with preoperative BCVA of 20/40 or worse were 5.9 times more likely to gain 2 or more Snellen lines at 1 year after CXL. Conversely, no baseline characteristic was found to correlate with treatment complications of continual topographic steepening or loss of vision. Corneal collagen cross-linking seems to be effective in decreasing progression of KC, with improvements in optical measures in many patients. Postoperative parameters discussed within this review followed a seemingly reproducible trend in their natural course over 12 months. Generally, the trend observed was immediate worsening between baseline and 1 month, resolution at approximately 3 months, and improvement thereafter. In predicting outcomes after CXL, no patient characteristics showed correlations with negative treatment outcomes such as loss of vision or continual topographic steepening. However, steeper KMax (≥55 D) and poorer BCVA (≤20/40) at the time of treatment correlated with better postoperative KMax and BCVA outcomes at 1 year, respectively. These outcome predictors should be considered when offering CXL to patients with KC or postoperative corneal ectasia.