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B. Lei, D. Dierks, K. Zhang, D.P. Hainsworth; Intravitreal Triamcinolone Acetonide Augments the Rod Electroretinogram (ERG) b–Wave in Rabbit . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1461.
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Purpose: Promising results have been observed with the use of intravitreal triamcinolone to improve the visual acuity of patients with diabetic macular edema and age–related macular degeneration. We investigate the clinical, histological, and electroretinographic effects of intravitreal triamcinolone acetonide suspension and its commercial supernatant in the rabbit retina. Methods: Eighteen New Zealand white rabbits were separated into 3 groups; each receiving an intravitreal injection in the right eye. Group 1 received 4 mg of commercially available triamcinolone acetonide; Group 2 received an equal volume (0.1 ml) of the steroid supernatant; and Group 3 received 4 mg of triamcinolone acetonide with the supernatant removed and replaced with balanced salt solution. The left eyes of the rabbits served as the control groups. The concentration of triamcinolone in the supernatant was measured by high–performance liquid chromatography (HPLC). Anterior segment, dilated funduscopic, dark– and light–adapted electroretinographic (ERG) examinations were performed at baseline and at 3–4 and 6–7 days after injection. Enucleated eyes were examined histologically. Results: Ocular examination revealed no differences among the groups. Eyes that received intravitreal triamcinolone (Groups 1 and 3) had a 10∼25% increase in dark–adapted ERG a– and b–wave amplitudes, as compared to control eyes, when subjected to stimulation with moderate– to high–flash intensities. A comparison of ERG responses of injected and control eyes revealed that the average ratio of injected eyes showed a significantly higher dark–adapted b–wave amplitude in Group 1 when compared to Group 2 at –0.83 log cd*s/m2 (p<0.05). No histological differences were observed between study and control eyes. Conclusions: Intravitreal injection of 4 mg of triamcinolone acetonide is not toxic to the rabbit retina. Triamcinolone may augment the rod–driven ERG responses, suggesting a mechanism by which visual function may improve in diseased retina.
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