Higher Risk of Light-Induced Retinal Damage Due to Increase of Intraocular Irradiance by Endoillumination.

INTRODUCTION: All applied illumination systems are validated according to a standard that measures in an experimental setup the direct radiation intensity on a surface in an aqueous solution, not involving an eyeball. Due to various factors, multiple intraocular light-tissue interactions could occur and lead to retinal irradiation intensities that are higher than the irradiation caused by direct illumination. The aim of this work is to investigate the hypothesis that intraocular and technical reference irradiance is different.

METHODS: Using an illumination system and a calibrated optical fiber, the irradiance in porcine eyes was measured at the posterior pole (macula) and compared with reference measurements. We compared two endoilluminators (spotlight and wide-angle) at a total of nine porcine eyes with a brown iris and five porcine eyes with a blue iris.

RESULTS: The intraocular irradiance was always significantly higher compared to reference measurements (p < 0.001). Between eyes with a blue or brown iris, no significant difference was observed.

CONCLUSION: A significantly higher irradiance could be measured compared to a reference measurement with the same illumination setup. The intraocular illumination increased between 30 and 60%, dependent on the distance of the distal end of the light fiber (4-12-mm distance to the retina). This leads to the assumption that the so far allowed "safe" exposure times for illumination systems are overestimated and the potential hazard to the retina is higher.