Corneal Collagen Cross-Linking: A Review of 1-Year Outcomes

Purpose:To review outcomes of corneal collagen cross-linking (CXL) for keratoconus (KC) or ectasia in a cornea subspecialty practice.Methods: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 (K-Max), 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 K-Max and BCVA, the preoperative patient characteristics examined were gender, age, disease group, cone location, thinnest pachymetry, UCVA, BCVA, and K-Max.Results:At 1 year, an average of 1.7 diopter (D) flattening in K-Max was found. Mean BCVA improved slightly more than 1 line (from 0.350.24 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 K-Max of 55 D or steeper were 5.4 times more likely to gain 2 D or more of K-Max 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.Conclusions: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 K-Max (55 D) and poorer BCVA (20/40) at the time of treatment correlated with better postoperative K-Max and BCVA outcomes at 1 year, respectively. These outcome predictors should be considered when offering CXL to patients with KC or postoperative corneal ectasia.