Ocular toxicity study of trypan blue injected into the vitreous cavity of rabbit eyes

Background: To evaluate the ocular toxicity of trypan blue (TB) injected in to the vitreous cavity of rabbit eyes. TB is a dye that could be useful for staining epiretinal membranes during vitrectomy surgery. Methods: Ten New Zealand White (NZW) rabbits underwent gas-compression vitrectomy. Rabbits w ere divided into three groups to receive injections of 0.1 ml basic salt so lution, 0.1 ml of a 0.06% TB solution or 0.1 ml of a 0.2% TB solution. Ocul ar toxicity was assessed by slit-lamp biomicroscopy, ophthalmoscopy, electr oretinography and histology. Results: Transient posterior capsule opacifica tion was noted in all animals. No significant reductions in a-wave or b-wav e amplitudes were found in any of the animals. Light and electron microscop ic examination of the inferior retina in the 0.2% TB-treated eyes showed da maged photoreceptors and marked disorganization. Immunohistochemical staini ng for rhodopsin was strongly reduced in those sections and staining for pr oliferation with Ki-67 was positive. No histological abnormalities were fou nd in the upper retina of the 0.2% TB-treated eyes or in any part of the re tina of the 0.06% TB-treated or control eyes. No histological abnormalities were found in any of the anterior chamber angle specimens. Conclusions: Al though no signs of toxicity were found after the prolonged presence of TB a t a concentration of 0.06% in the vitreous cavity of rabbit eyes, marked da mage occurred in the lower retina of 0.2% TB-treated eyes. The shortterm pr esence of TB at a concentration of 0.06% in the vitreous cavity is harmless to the rabbit eye but a higher concentration of TB could be unsafe.