Purpose: To investigate the toxicity of indocyanine green (ICG) on retinal cells using cultured retinal pigment epithelium (RPE) cells and the effects of intravitreous injection of ICG into rat eyes. Methods: Cultured RPE cells were exposed to various concentrations of ICG for 2 min, a viability assay was performed 1 day after exposure. For an in vivo study, 5 μl of ICG (5 or 25 mg/ml) were injected into the vitreous cavity of rat eyes, which were examined 1,3 and 7 days after the injection by histological and glutamine synthetase (GS) immunohistological evaluation. Results: Viabilities of RPE cells were decreased dependent on the ICG dose. In the histological evaluation, we observed differences of effects of ICG between the central retinal area and the peripheral area. ICG injection caused degeneration of all retinal layers in the central retinal area. GS immunoreactivities decreased by ICG injection, which corresponded to an area of severe destruction. Conclusion: A high concentration of ICG may cause toxic effects on retinal cells. Mueller cell dysfunction may play some role in the retinal toxicity caused by ICG.
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