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EVALUATION OF THE TOXICITY OF SUBRETINAL TRIAMCINOLONE ACETONIDE IN THE RABBIT

Purpose: Subretinal triamcinolone acetonide (TCA) might be a useful adjuvant in the treatment of subretinal neovascularization. The purpose of this study was to test the toxicity of subretinal TCA in the rabbit eye. Methods: Sixteen New Zealand rabbits were vitrectomized and injected with either decanted TCA solution or vehicle. The concentration of injected TCA was 2 mg, and the delivered volume was 10 &mgr;L. Rabbits were examined on days 1, 3, and 7 and then once a week up to 3 months after surgery. Optical coherence tomography was performed at months 1, 2, and 3. After the last examination, which included electroretinography, the rabbits were killed, and the eyes were enucleated for histopathologic analysis. Results: Subretinal TCA appeared as a white circumscribed deposit. As the drug disappeared, areas of hyperpigmentation were seen adjacent to the drug deposit. Electroretinography tracings were normal, indicating no widespread toxic effect. Histologic analysis revealed areas of absence and/or hyperpigmentation of the retinal pigment epithelium and damage to photoreceptors and the outer nuclear layer of the retina. Conclusion: Subretinal injection of TCA crystals can be toxic to the outer retina and retinal pigment epithelium. Whether the potential beneficial effect of such a high-dose steroid in limiting subretinal inflammation, angiogenesis, and proliferation outweighs toxicity can only be determined from a clinical trial.