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Z. I. Gatzioufas, P. Charalambous, C. Jonescu-Cuypers, S. Thanos, B. Seitz; Potential Retinal Toxicity of Indocyanine Green in an Animal Model. Invest. Ophthalmol. Vis. Sci. 2007;48(13):86.
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© ARVO (1962-2015); The Authors (2016-present)
Indocyanine green (ICG) is a vital dye widely used in macula hole surgery for staining and thereby improved visualisation of the internal limit membrane. The aim of our study was to investigate in vivo the effects of ICG on the retina using an experimental animal model.
Intravitreal injections of ICG in a dosage of 5µl at concentrations of 5 and 25mg/ml, were applied in two groups with six Sprague Dawleys rats each, respectively. In a third group of six rats the same amount of PBS was intravitreally injected (sham group). All groups were examined electrophysiologically (standard ERG, pattern ERG) preoperatively and one, two and three weeks postoperatively. During the third postoperative week the rat retinas were stained in vivo with Fluorogold using a retrograde labelling technique. After four days all retinas were removed micro-surgically and subjected to fluorescence microscopy. Four randomized selected retinas from each group were examined immunohistochemically with GAP43 and Rhodamin. Finally, semi-thin slices were prepared from two retinas from each group and examined by phase-contrast microscopy.
The electrophysiological examination revealed a significant reduction of the a- and b-wave amplitudes in the ICG-treated groups during the second postoperative week, both in scotopic and photopic ERG (p<0.05). The latency was also significantly increased compared to the sham group (p<0.05). Retrograde staining showed a decrease in the mean retinal ganglion cell number in the ICG-treated retinas. Immunohistochemistry demonstrated a strong signal for GAP43 and reduced expression of Rhodamin in the ICG-treated retinas compared to the sham retinas. Phase contrast microscopy confirmed the thinning and degradation of the photoreceptors layer in the ICG-treated retinas.
Our results suggest that intravitreal injection of ICG may have a major toxic impact on the rat retina, affecting all retinal layers and especially the photoreceptors and the retinal pigment epithelium. This indicates that ICG use in vitreoretinal surgery should be thoroughly considered in view of the potential retinal toxicity.
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