Effects of light exposure, pH, osmolarity, and solvent on the retinal pigment epithelial toxicity of vital dyes

To investigate the in vitro effect of pH, osmolarity, solvent, and light interaction on currently used and novel dyes to minimize dye-related retinal toxicity.Laboratory investigation.Retinal pigment epithelium (RPE) human cells (ARPE-19) were exposed for 10 minutes to different pH solutions (4, 5, 6, 7, 7.5, 8, and 9) and glucose solutions (2.5%, 5.0%, 10%, 20%, 40%, and 50%) with osmolarity from 142 to 2530 mOsm, with and without 0.5 mg/mL trypan blue. R28 cells were also incubated with glucose (150, 310, and 1000 mOsm) and mannitol used as an osmotic control agent in both experiments. Dye-light interaction was assessed by incubating ARPE-19 for 10 minutes with trypan blue, brilliant blue, bromophenol blue, fast green, light green, or indigo carmine (0.05 mg/mL diluted in balanced saline solution) in the presence of high-brightness xenon and mercury vapor light sources.Solutions with nonphysiologic pH, below 7 and above 7.5, proved to be remarkably toxic to RPE cells with or without trypan blue. Also, all glucose solutions were deleterious to RPE (P.001) even in iso-osmolar range. No harmful effect was found with mannitol solutions. Among the dyes tested, only light green and fast green were toxic to ARPE-19 (P.001). Light exposure did not increase RPE toxicity either with xenon light or mercury vapor lamp.Solutions containing glucose as a dye solvent or nonphysiologic pH should be used with care in surgical situations where the RPE is exposed. Light exposure under present assay conditions did not increase the RPE toxicity.