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

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 mu m) than the 144 who did not (57.0 +/- 8.2 D, P = 0.05; 454.6 +/- 45.4 mu m, P = 0.08). A corneal curvature of >60 Dand a pachymetry of <425 mu m 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 3.5-3.7mW/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.