Abstract
BackgroundIndocyanine green (ICG) dye is commonly used to stain the inner limiting membrane during macular surgery. There are reports documenting the toxicity of ICG on retinal pigment epithelial cells, with conflicting results in retinal ganglion cells. In the present study, we evaluated the effect of ICG on retinal ganglion cells in vitro.Cultured rat retinal ganglion cells (RGC-5) were exposed to different concentrations of ICG (0.25, 0.5, 1.0, 1.25, & 5 mg/ml) and at various time intervals (1, 5, 15, 30, & 60 minutes). Changes in structural morphology were identified using phase contrast bright field microscopy. Cell viability was quantified using the neutral red assay and cell death was characterized using Annexin-V staining.FindingsSignificant morphologic changes were observed at the 15 and 60 min intervals for all concentrations, where a reduction in cell size and loss of normal spindle shape was noted. A dose dependent decrease in cell viability was observed with increasing concentration of ICG as well as increasing exposure intervals. Compared to control, 48-74% reduction in neutral red uptake at all concentrations for exposures 5 min or greater (p < 0.001). Even at 1 min exposure, a dose dependent decline was observed in cell viability, with a 28-48% decline for doses above 1.25 mg/ml (p = 0.007). Staining with Annexin-V, demonstrated a similar dose and time dependent increase in number of cells exhibiting early apoptosis. A greater than two-fold increase in Annexin-V expression for all doses at exposures greater than 1 min was noted.ConclusionICG dye exhibits toxicity to retinal ganglion cells at clinically relevant doses following 1 min exposure.
Highlights
Indocyanine green (ICG) dye is commonly used to stain the inner limiting membrane during macular surgery
Cell Viability Assay (Neutral Red) retinal ganglion cell (RGC) cells exposed to concentrations as low as 0.25 & 0.5 mg/ml demonstrated reduced neutral red (NR) uptake as early as 1 min
Indocyanine green (ICG) is an amphillic tricarbocyanine dye often used in macular surgery, where it stains the internal limiting membrane and facilitates its removal [16]
Summary
Indocyanine green (ICG) dye is commonly used to stain the inner limiting membrane during macular surgery. We evaluated the effect of ICG on retinal ganglion cells in vitro. The safety of intravitreal use of ICG is not well established Adverse effects such as visual field defects [7,8,9] and atrophy of the retinal ganglion cell layer [10] subsequent to ICG assisted membrane peeling have been reported. The retinal ganglion cell (RGC) layer is the first to come in contact with ICG dye used for staining in macular surgery and theoretically has the maximum exposure to the dye. A number of animal and in-vitro studies have evaluated the toxicity of ICG in cell culture models [13,14,15,16,17,18]. There is conflicting data with regards to presence of ICG mediated toxicity
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