Toxicity of indocyanine green injected into the subretinal space - Subretinal toxicity of indocyanine green

Purpose: To evaluate the toxicity of indocyanine green (ICG) injected into the subretinal space. Indocyanine green may come in contact with photoreceptors and retinal pigment epithelium through a macular hole during ICG-assisted peeling of the internal limiting membrane. Methods: Balanced salt solution or ICG of various concentrations (0.6, 1.25, 2.5, or 5.0 mg/mL) was injected into the subretinal space of rabbit eyes and removed after 1 minute. After 3 days, 1 week, and 4 weeks, the eyes were enucleated and evaluated by light microscopy and electron microscopy. Results: When the ICG of 1.25 mg/mL or higher concentration was injected into the subretinal space, degenerative changes of the photoreceptors and the retinal pigment epithelial cells were found after 3 days with light and electron microscopy. After 1 week, the outer retina was disintegrated and the photoreceptors were not found. After 4 weeks in the eyes with 1.25 mg/mL ICG, short photoreceptors and a thin outer nuclear layer were seen. In the eyes with 2.5 mg/mL or higher ICG, the photoreceptors and the outer nuclear layer were destroyed completely. Conclusion: The results of this study suggest that the ICG of 1.25 mg/mL or higher concentration has toxicity to the outer retina of the rabbit and may cause adverse effects on the functional outcome after macular hole surgery.