Safety Testing of Indocyanine Green in Retinal Perfusion Organ Culture

Abstract

Abstract: : Purpose: To assess potential retinal toxicity of indocyanine green (ICG) in a perfusion organ culture model. Methods: Retina–RPE–choroid specimens were isolated from porcine eyes within 3 hours post–mortem. The retinal surface was exposed to ICG dissolved in glucose 5% at 0.1% and 1% concentrations for 1 min and 30 min. Simulating the intraoperative application of ICG the retinal surface was illuminated with a standard surgical light pipe for 3 min. Specimens were kept in perfusion organ culture for up to 48 hours. Retinal tissue sections were examined by light microscopy 24–48 hours following exposure to ICG and illumination. The presence of apoptosis in retinal tissue sections was investigated with the TUNEL–technique. Apoptosis was quantified by a grading system. Additional control tissue samples were treated with DNAase to cleave DNA from cell nuclei to induce apoptosis. Fluorescence microscopy was used to localise ICG in retinal tissue sections following 1 min, 10 min, 30 min, and 60 min of exposure to ICG 0.1% and 1%. Results: Following exposure for 1 min and 30 min ICG penetrated the inner retina over time from the inner surface maximally to the ganglion cell layer. We did not observe significant TUNEL–positive cells in control retinal tissue and in retinal tissue exposed to either ICG 0.1% or 1% for 1 min. Retinal tissue samples exposed to ICG and controls showed no significant signs of cell necrosis. Mild degree apoptosis was found following 30 min exposure to either ICG 0.1% or 1%. TUNEL–positive cells were abundant in DNAase–treated retinal tissue samples and in the photoreceptor layer of all retinal tissue samples after 48 hours in perfusion organ culture. Conclusions: ICG applied to the retinal surface penetrates the retina over time. ICG 0.1% and 1% induce apoptosis but not necrosis in the inner retinal layers following exposure to ICG for 30 min and illumination for 3 min. A short exposure time of 1 min simulating the intra–operative application of either ICG 0.1% or 1% with illumination of 3 min does not induce apoptosis or necrosis in the inner retinal layers.

Keywords: pharmacology • retina • retinal culture