Illumination system for corneal collagen crosslinking

Purpose. We have designed and constructed an ultraviolet (UV) illumination system for use in corneal collagen crosslinking (CXL) procedures. CXL is a recently developed procedure to treat Keratectasia such as Keratoconus and Pellucid Marginal Degeneration. The role of the illumination system is to safely provide UV light at the absorption peak of the Riboflavin photosensitizer, which generates reactive oxygen species and subsequently increases the number of covalent bonds between collagen fibrils. Methods. Raytracing simulations were used to compare various optical designs for the illumination system. Alternative layouts are presented and design compromises between competing goals are discussed in reference to safety and practical considerations for clinical use. The mechanical mounting system and the beam output power and beam diameter testing system are briefly described. Results. The illumination system has several features that help provide uniform effectivity of the applied treatment over the desired treatment diameter, assuming Riboflavin has uniform absorption in the treatment zone. The optical design offers substantially greater beam control and safety than rudimentary devices relying on direct illumination. The prototype was relatively inexpensive to construct and includes a mounting system and beam testing setup. Conclusions. The UV illumination system was found to be successful in providing a balanced solution regarding clinical use and the eye safety issues relevant to CXL.