Effects Of Light Exposure, pH, Osmolarity And Solvent On The Retinal Toxicity Of Vital Dyes In Chromovitrectomy

Abstract

Purpose: : To investigate the influence of pH, osmolarity, solvent and dye-light interaction in currently use and novel dyes in order to identify the deleterious effects of dye-related retinal toxicity.

Methods: : Cultured cells derived from human retinal pigment epithelium (RPE), ARPE-19 were exposed to seven different BSS solutions with and without trypan blue (TB) 0.5 mg/ml with adjusted values of pH (4; 5; 6; 7; 7.5; 8 and 9), with osmolarity ranging from 317-345 mOsm, and to other seven glucose solutions with and without TB 0.5 mg/ml (2.5; 5.0; 10; 20; 30; 40; 50%), with osmolarity ranging from 142 to 2530 mOsm with pH of 7.0-7.6, for 10 minutes. Mannitol solutions were used as an osmotic control agent. ARPE -19 cells were also incubated with 0.05 mg/ml of six dyes diluted in BSS - TB, brilliant blue (BriB), bromophenol blue (BroB), fast green (FG), light green (LG) and indigo carmine (IC) - in the presence of two different light sources (high brightness xenon and mercury vapor) for 10 minutes to evaluate dye-light interaction. Cell viability was asessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. The ANOVA statistical test was used to compare the cell viability results.

Results: : Solutions with a non-physiological pH, below 7 and above 7.5, proved to be remarkable toxic to RPE cells even without TB. All solutions containing glucose were significantly more deleterious than the BSS control (p<0.001) even in an iso-osmolar range. Mannitol solutions did not lead to any harm effect in all solutions tested. Among tested dyes, only LG and FG were toxic to RPE cells (p<0.001). Light exposure did not increase retinal toxicity either with the xenon light or with the mercury vapor lamp. Evaluating dye light-interaction,TB was statically different from BriB when exposed to mercury light; also, IC had a decrease in cell viability compared to BriB with xenon light.

Conclusions: : Several factors may contribute to increase the toxicity effect of the dye in the retina. Non-physiologic values of pH and the use of glucose as a solvent appear to be more deleterious to the RPE cells than the dye itself. Light exposure with the stained retina should not be a concern when xenon or mercury vapor is used as light source and specially when applied in a short period of time.

Keywords: retinal pigment epithelium • drug toxicity/drug effects • vitreoretinal surgery