Anders Behndig

Purpose To analyse the temperature of the corneal surface in keratoconus during corneal customized crosslinking (CXL) with a preserved epithelium (epi‐on) under oxygen flow, and epi‐off CXL in room air, and to assess the effect of pre‐heating the oxygen. Methods This masked, intra‐individual comparing randomized study included 14 participants with bilateral progressive keratoconus treated with bilateral CXL: one eye with epi‐on CXL under a flow of 2.5 L/min oxygen; the fellow eye with epi‐off CXL in room air. In a second setting involving 12 healthy participants, room‐tempered oxygen was flushed over one eye and oxygen pre‐heated to 37°C over the fellow eye. The corneal surface temperature was assessed with infrared photography. Results A reduction in corneal surface temperature was seen from the pre‐treatment application of topical riboflavin in the epi‐off group (−1.1 ± 1.0°C, p < 0.001). The temperature increased during the first half of the CXL treatment in both groups (+0.7 ± 1.2°C, p = 0.041 for epi‐on; +0.7 ± 0.9°C, p = 0.023 for epi‐off CXL, respectively). In epi‐on CXL an overall temperature increase was seen during the treatment (+0.8 ± 1.2°C, p = 0.016). In the second setting, pre‐heating the oxygen rendered a surface temperature increase of +1.8 ± 0.2°C ( p < 0.001). Conclusion In epi‐off CXL, the application of topical room‐tempered riboflavin decreases the corneal surface temperature, likely due to increased evaporation. A slight temperature increase is seen during CXL with both epi‐on and epi‐off CXL, albeit far below the corneal safety limit. The corneal temperature can, however, be increased by applying pre‐heated oxygen, a possible approach to modify or augment the treatment effect in CXL.