Retinal toxicity of indocyanine green in albino rabbits

PURPOSE. Intravitreal indocyanine green (ICG) is commonly used in vitreoretinal surgery. The purpose of this study was to evaluate possible toxicity of ICG in the retina of albino rabbits. METHODS. Twenty-two albino rabbits were injected intravitreally with 0.1 mL ICG solution in one eye, and three rabbits were studied for the effects of 0.1 mL distilled water. All rabbits were injected intravitreally with 0.1 mL saline into the fellow eye, which served as the control. The electroretinogram (ERG) and visual evoked potential (VEP) were recorded from each rabbit at different time intervals after injection. The rabbits were killed at the termination of the follow-up periods and their retinas prepared for histologic examination at the light microscopic level. RESULTS. Three hours after injection, the ERG responses were reduced in amplitude in all ICG-injected eyes, and the VEPs were of abnormal pattern (reduced amplitude and delayed). Partial dose-dependent recovery was observed during 4 weeks of follow-up. Light microscopy of the retinas of the experimental eyes exhibited considerable damage to all retinal layers in all eyes studied that received the highest ICG dose. CONCLUSIONS. ICG is potentially toxic to all retinal layers of the albino rabbit. Although it is difficult to extrapolate these findings directly to human eyes, caution should be exercised when using ICG intravitreally.