INHIBITION OF PRERETINAL AND OPTIC-NERVE HEAD NEOVASCULARIZATION IN PIGS BY INTRAVITREAL TRIAMCINOLONE ACETONIDE

Purpose: The authors tested the antiangiogenic properties of intravitr eally administered triamcinolone acetonide in a pig model of preretina l neovascularization to determine the effectiveness of this therapy in preventing neovascularization. Methods: In 14 eyes of seven pigs, bra nch retinal vein occlusions were created in a standardized manner usin g photodynamic thrombosis with rose bengal dye and thermal burns from the argon green laser, Intravitreal injection of approximately 4 mg of triamcinolone acetonide was performed in one eye of each animal, and eyes were followed clinically for 12 weeks with ophthalmoscopy and fun dus photography. A standardized grading system was developed to permit masked assessment of disc proliferations from fundus stereophotograph s, After death, all neovascularization was confirmed histopathological ly and a final grade was assigned to each eye, Statistical analysis em ployed use of a nonparametric test of the paired data. Results: Signif icant inhibition of neovascularization was observed in triamcinolone-t reated eyes (P = 0.0156). Although none of the steroid-injected eyes d emonstrated clinically evident new vessels, histopathologic and photog raphic analysis results demonstrated fine new vessels on the optic dis c in four eyes. In all of the untreated eyes, neovascularization of a moderate (II) to high (III to IV) grade developed, Conclusions: Intrav itreal triamcinolone acetonide effectively inhibited preretinal and op tic nerve head neovascularization in the pig model. The grading system used permitted masked assessment of outcome and paired analysis allow ed a conclusion to be drawn from a relatively small number of eyes. Th e mechanisms by which triamcinolone acetonide inhibits neovascularizat ion remain to be elucidated.