Retinal function and histologic changes following intravitreal injection of indocyanine green in a rabbit model

The aim of this animal study was to investigate the effects of intravitreal injection of indocyanine green (ICG) applied in macular hole surgery on retinal functional, morphology, and histologic changes. Eighteen (18) New Zealand albino rabbits were divided equally into three groups (6 rabbits in each). In Group A, both eyes of each rabbit were vitrectomized by perflouropropane gas compression. One (1) month later, 0.1 cc of different doses of ICG was injected into the vitreous in the left eyes. In the right eyes, 0.1 cc of balanced salt solution was injected intravitreally, allowing them to serve as control eyes. In Group B, the same doses of ICG were injected intravitreally. ICG was washed out by fluid-fluid exchange 3 minutes after injection. In Group C, the same doses of ICG were injected intravitreally in nonvitectomized eyes. Scotopic and photopic electroretinogram (ERG) recordings and indirect ophthalmoscopy examinations were performed to detect any functional and morphologic changes. Rabbit eyes were enucleated 4 months after ICG injections to observe histologic changes. Significant decreased of scotopic and photopic ERG amplitude and marked histologic changes were noted in eyes injected with 0.5 mg/cc and 0.1 mg/cc of ICG in nonvitrectomized eyes (Group C). In vitrectomized eyes (Group A), decreased scotopic and photopic ERGs and mild histologic changes were noted in eyes injected with 0.5 mg/cc, but no histologic changes were noted in eyes injected with 0.1 mg/cc. There was a transient, mild decrease in scotopic and photopic ERGs and no morphologic changes were noted in the eyes with fluid-fluid exchange (Group B). The toxicity of intravitreous ICG is dose- and time-dependent. ICG at 0.5 mg/cc, with short exposure time, is recommended in macular hole surgery.