RESUMEN
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 cross-linking (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 pre-operative 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/cm(2), 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.