Chemical toxicity of indocyanine green damages retinal pigment epithelium.

PURPOSE To investigate the chemical toxicity of indocyanine green (ICG). METHODS Surface active and precipitating effects of ICG were quantitatively analyzed by determining bovine serum albumin dissolved or precipitated in the presence or absence of salt solutions. The effects of precipitation on serum and cytotoxicity were evaluated by measuring the viability of retinal pigment epithelium (RPE) in vitro. RESULTS ICG functioned as a surfactant without salts, but with nearly physiological concentrations of balanced salts, it functioned as a unique precipitating factor. This rendered the soluble molecules in serum that are indispensable in the culture of RPE cells insoluble during a 12-hour exposure, resulting in poor cell survival in vitro. Cytotoxicity in serum-free medium was also shown during brief exposures. CONCLUSIONS Commonly used dosages of ICG directly applied into the vitreous cavity, which not only contact the retina but also invade the space between the retina and RPE through a macular hole, may be sufficient to induce retinal disorders after the damaging chemical property of ICG has disturbed the microenvironment.