Neurotoxic effects of trypan blue on rat retinal ganglion cells

To facilitate the peeling of internal limiting membrane or epiretinal membrane in vitreoretinal surgery, trypan blue (TB) and indocyanine green (ICG) have been used. However, the cytotoxicity of these dyes have been concerned. The aim of this study was to investigate the neurotoxic effects of TB on rat retinal ganglion cells (RGCs) and compare the effect of TB with ICG. Rat RGCs were purified by a two-step immunopanning procedure. In short-time exposure experiments, purified RGCs cultured for 3 days were exposed to 600 mgL(-1) TB, 1500 mgL(-1) TB and 1500 mgL(-1) ICG for 10 sec to 30 min. The number of viable RGCs was counted after 12 hr in culture. In long-time exposure experiments, purified RGCs were cultured for 3 days in TB solutions ranging from 2 to 800 mgL(-1) or in ICG solutions at concentrations from 2 to 250 mgL(-1). Then the number of viable cells was counted. Exposure to 600 mgL(-1) TB, 1500 mgL(-1) TB and 1500 mgL(-1) ICG for short time from 10 sec to 30 min caused a time-dependent damage to RGCs. There was no significant difference in cytotoxicity to RGCs between TB and ICG in short-time exposure. In long-time exposure, TB as well as ICG showed neurotoxic effect on RGCs in a dose-dependent manner. Fifty percentage inhibitory concentration (IC50) of TB to RGCs was calculated as 115 mgL(-1), while that of ICG was 33 mgL(-1). In conclusion, TB induced neurotoxic effect on RGCs in a dose- and time-dependent manner. During the short-time exposure in surgery, there is likely no difference in neurotoxic effect on RGCs between TB and ICG. However, once the dyes are left in the eyes after surgery, TB may show less toxicity on RGCs than ICG.