PURPOSE: Previous work has shown that indocyanine green (ICG)-assisted peeling of the inner limiting membrane (ILM) may cause retinal damage. In this study, a toxic and a photodynamic effect of ICG at the vitreoretinal interface was assumed. METHODS: Ten human donor eyes were hemisected, and 0.05 mL of 0.05% ICG was poured over the trephined macula in eight eyes. After 1 minute, the dye was drained by irrigation. The macula in each of two eyes was illuminated for 3 minutes with wavelengths of 380 to 760, 380 to 620, or 620 to 760 nm. Two eyes were treated with ICG only, and two eyes were illuminated only. Retinal specimens from the macula and the untreated retina were processed for light and electron microscopy. The irradiance of the light source and the absorption properties of ICG were measured. RESULTS: Exposure of the ICG-stained ILM to wavelengths beyond 620 nm resulted in severe damage to the inner retina, including loss of ILM, cellular disorganization, and fragmentation of the cytoplasm. ICG staining alone or in combination with wavelengths of 380 to 620 nm disclosed rupture of Müller cells with detachment of the ILM, but no other cellular disorganization. Eyes subjected to illumination only showed no abnormalities. CONCLUSIONS: The spectral absorption properties of ICG may account for a possible photodynamic effect of ICG at the vitreoretinal interface. ICG alone induces ILM detachment and disruption of Müller cells even without intentional peeling of the membrane. It is assumed that accumulation of the dye at the vitreomacular interface may enhance the concentration and osmolarity of ICG at the retina beyond intravitreous values and critical limits.
PURPOSE: Previous work has shown that indocyanine green (ICG)-assisted peeling of the inner limiting membrane (ILM) may cause retinal damage. In this study, a toxic and a photodynamic effect of ICG at the vitreoretinal interface was assumed. METHODS: Ten humandonor eyes were hemisected, and 0.05 mL of 0.05% ICG was poured over the trephined macula in eight eyes. After 1 minute, the dye was drained by irrigation. The macula in each of two eyes was illuminated for 3 minutes with wavelengths of 380 to 760, 380 to 620, or 620 to 760 nm. Two eyes were treated with ICG only, and two eyes were illuminated only. Retinal specimens from the macula and the untreated retina were processed for light and electron microscopy. The irradiance of the light source and the absorption properties of ICG were measured. RESULTS: Exposure of the ICG-stained ILM to wavelengths beyond 620 nm resulted in severe damage to the inner retina, including loss of ILM, cellular disorganization, and fragmentation of the cytoplasm. ICG staining alone or in combination with wavelengths of 380 to 620 nm disclosed rupture of Müller cells with detachment of the ILM, but no other cellular disorganization. Eyes subjected to illumination only showed no abnormalities. CONCLUSIONS: The spectral absorption properties of ICG may account for a possible photodynamic effect of ICG at the vitreoretinal interface. ICG alone induces ILM detachment and disruption of Müller cells even without intentional peeling of the membrane. It is assumed that accumulation of the dye at the vitreomacular interface may enhance the concentration and osmolarity of ICG at the retina beyond intravitreous values and critical limits.