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In Vivo Toxicity Study of Rhodamine 6G in the Rat Retina

¹From the Centre for Ophthalmology, University of Tübingen, Tübingen, Germany; the ²Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany; the ³Tadeusz Krwawicz Chair of Ophthalmology and 1st Eye Hospital, Medical University of Lublin, Poland; the ⁴Department of Anatomy, Medical Faculty Carl Gustav Carus, Technical University of Dresden, Germany; and the ⁵Department of Experimental Pharmacology, PAS Medical Research Center, Warsaw, Poland.

PURPOSE. To investigate the intraocular effect of rhodamine 6G (R6G) on retinal structures and function in an in vivo rat model and to develop an in vivo method for accurate evaluation of new dyes for intraocular surgery.

METHODS. R6G in physiologic saline solution (PSS) was injected into the vitreous of adult Brown Norway rats at concentrations of 0.0002%, 0.002%, 0.02%, 0.2%, and 0.5%. Control animals received only PSS. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts, light microscopy 7 days later, photopic electroretinography (ERG), and measurement of scotopic sensitivity and recovery of dark adaptation 48 hours and 7 days after intravitreous injection.

RESULTS. R6G at concentrations of 0.2% and 0.5% led to a dose-dependent loss of RGC. The most significant loss occurred at 0.5%. Lower concentrations (0.0002%, 0.002%, and 0.02%) produced no statistically significant retinal ganglion cell loss. Analysis of the eyes by light microscopy showed no structural changes in the central retina, although injections of 0.5% R6G were followed by impressive degenerative changes adjacent to the injection sites. ERGs showed no effects of the highest R6G concentration on rods, kinetics of rhodopsin recovery after bleaching, or cone-driven responses.

CONCLUSIONS. R6G can be safely injected in doses of up to 0.02% in rats, but has a toxic effect on retinal ganglion cells at higher concentrations. Accumulation of R6G may be a problem at higher concentrations, particularly at the injection site.

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				C Haritoglou, T Kreutzer, R Tadayoni, H Langhals, C A May, S Thaler, and A Kampik Staining and peeling of the internal limiting membrane using a fluorescent dye (Rhodamine 6 G) Br. J. Ophthalmol., September 1, 2008; 92(9): 1265 - 1268. [Abstract] [Full Text] [PDF]