Sterile keratitis after combined riboflavin-UVA corneal collagen cross-linking for keratoconus

Abstract

Purpose: To investigate patient risk factors and to look for potential causes of sterile infiltrates following an unexpected cluster of sterile keratitis after a routine collagen crosslinking (CXL) list. Methods: The records of all 148 cases of CXL were reviewed retrospectively. The equipment and solutions used and our clinic's standard operating procedure for CXL were reviewed. An in-vitro experiment to explore the variation in ultraviolet A (UVA) irradiance from fluctuations in the working distance of the UVA lamp was conducted. Results: The four patients who developed sterile infiltrates had steeper maximum corneal curvatures (68.0±7.3 D) and thinner pachymetry (389.9±49.0 μm) than the 144 who did not (57.0±8.2 D, P = 0.05; 454.6±45.4 μm, P = 0.08). A corneal curvature of >60 Dand a pachymetry of <425 μm were significant risk factors. All four affected cases obtained a complete resolution with topical antibiotics and steroids. The unaided VA and the maximum K improved from their preoperative levels in three out of four patients. A 2-mm reduction in distance of the VEGA C.B.M. X-Linker from a treated surface increased irradiance to 3.5-3.7 mW/cm2, which is above the threshold for endothelial toxicity. Conclusion: Patients with thinner and steeper corneas are at an increased risk of developing sterile keratitis. The visual outcomes despite this complication are good.