Effects of Indocyanine Green Dye (ICG) on the Retina and Retinal Pigment Epithelium in a Porcine Model of Retinal Hole

Abstract

Abstract: : Purpose: This study was designed to emulate human macular hole surgery in the young pig model and to test the effects of ICG on the retina and retinal pigment epithelium (RPE) by clinical and histological examination. Our objective was to determine whether intravitreal ICG ( in different concentrations ) can cause retinal and RPE cell damage. Methods: Yorkshire Cross pigs (n=23) underwent vitrectomy with posterior vitreous detachment. A small retinal bleb was created with infusion fluid in the posterior pole following which a single retinal hole was created within the bleb with the vitreous cutter. In 3 study groups (n=6, each group) an air-fluid exchange was performed following which either balanced salt solution (BSS), 1.0% ICG or 0.5% ICG was applied over the retinal hole and allowed to remain for 1 minute before washing out by restarting the infusion. In one additional groups of animals (n=5) 0.5% ICG was injected into the eye while it was still filled with infusion fluid. At 4 weeks the eyes were examined clinically and fundus photographs were obtained prior to enucleation and light microscopic histology. Two masked observers examined the fundus photographs and graded them for retinal and RPE abnormalities. Results: Air-filled eyes exposed to 1.0% or 0.5% ICG showed a statistically significant increased degree of RPE atrophy compared to air-filled eyes exposed to BSS (controls) and fluid-filled eyes and exposed to 0.5% ICG (p=0.036). Histological evaluation did show a statistically significant increase in retinal outer segment degeneration in air-filled eyes exposed to either 1.0% or 0.5% ICG compared to controls and fluid-filled eyes exposed to 0.5% ICG (p=0.0438). None of the study groups showed retinal inner segment degeneration. Conclusions: In a porcine study emulating human macular hole surgery, retina exposed to ICG concentrations used in humans showed RPE atrophy, hypopigmentation and outer segment degeneration. Eyes filled with infusion fluid during ICG injection showed less damage to the RPE and outer retina than when ICG was injected into the air-filled eye.

Keywords: macular holes • drug toxicity/drug effects • vitreoretinal surgery