Effect of Intravitreal Triamcinolone on Retinochoroidal Healing Processes After Argon Photocoagulation

Abstract

Abstract: : Purpose: Analyse the effects of intra vitreous injection of Triamcinolone on the wound healing processes after argon laser retina photocoagulation . Methods: Wild type C57BL/6J mice, 6 to 8 months old underwent a standard argon laser photocoagulation protocol. After pentobarbital anesthesia and pupil dilatation, fundus photocoagulation lesions were induced (one impact, 50µm, 400mW, 0.05sec). The photocoagulated mice were divided in three groups: Group I (n=12), any intra vitreous injection. Group II (n=12), intra vitreous injection of 1 µl Balanced Salt Solution . Group III (n=25), intra vitreous injection of 1 µl containing 1.5, 3, 7.5, 15, 30 or 75 µg Triamcinolone acetonide in BSS. One, 3, 7, 14, 21 and 28 days after photocoagulation, two animals from each Group were sacrificed. At random, one eye from each treatment group is fixed in Bouin and processed for conventional histology and three eyes are mount in Tissue tek (OCT), snap frozen, cut and processed for immuno–histochemistry. Specific antibodies against GFAP, von Willebrand factor and F4/80 were used . TUNEL reaction was also carried out along with nuclear DAPI staining. A systematic analysis of the cellular remodelling processes taking place within the laser lesion and its vicinity was performed . Results: In Groups I and II, few hours following the argon laser beam, a localized affection of the RPE cells and choroid is observed with minimal or no affection of the retinal layers. Apoptotic cells (TUNEL positive) are observed mostly located in the retinal outer nuclear layer. Intense staining with GFAP is associated with activated retina astrocytes and Müller cells. Around the 7^th day, new capillaries of choroidal origin are detected at the external edges of the laser lesion. These processes are accompanied by the infiltration of inflammatory cells within the lesion. In Group III, mice treated with low Triamcinolone doses decreased the number of infiltrating inflammatory cells and inhibited the development of new choroidal capillaries. Higher doses of Triamcinolone are toxic even lethal and increase the apoptotic activity of the retinal nuclear layers. The vessels detected within the lesion at the choroid level were of retinal origin.Conclusions: Intravitreous injection of low doses of Triamcinolone influence markedly the remodelling and healing processes with a major effect on the extent of cell infiltration and development of choroidal capillaries.

Keywords: retina • laser • choroid: neovascularization