Retinal Toxicity Of Preservative-free FDA-approved Triancinolone (Triesence®) In Rabbit Eyes: A Morphologic And Electroretinographic Study

Abstract

Purpose: : To evaluate the effects of commercially available preservative free triamcinolone acetonide (Triesence®) on an in-vivo rabbit model.

Methods: : 30 Dutch belted rabbits were assigned to 3 different intravitreal drug concentrations of Triesence: 1, 4 or 8 mg. The animals were anesthetized and the right eye received drug, while the left received balanced salt solution. After 30 days the animals were sedated and electroretinogram (ERG) was recorded. After the ERG, the animals were euthanized and the eyes were collected for morphological analysis. 12 other rabbits had histology only analysis after 7 days of injection. ERGs were recorded with the RETIport system (Roland Consult, Germany) with a Ganzfeld Q450 SC stimulator. Stimulation protocol was : scotopic condition: flashes at 0.01, 3.0, and 10 cd.s/m² and photopic flicker of 30 cd.s/m² at 12 18, 24, and 30 Hz, with 30 cd.s/m² background Amplitudes and implicit times of the a-wave and b-wave components and amplitudes of the FFT first harmonic were used to analyze the responses. Wilcoxon signed rank test was used to compare related samples.

Results: : Dark-adapted ERGs did not show any difference between drug and control groups. Light-adapted ERGs had smaller b-wave amplitudes in the 4 and 8 mg groups (p<0.05), but not in the 1mg group. There was a reduction in flicker amplitude at 24 and 30 Hz in the 8mg group and at 30Hz in the 4mg group (p<0.05). For 12 and 18Hz in the 8mg group p= 0.05. No difference was observed in Hematoxylin-Eosin, Tunnel, Fluoro-Jade B and glial fibrillary acid protein (GFAP) between any experimental and control retinas after 30-day injection. However, after 7 days, retinas from the 8mg group showed GFAP-positive processes of Muller glial cells at the bottom part of the retina, where the drug was sited.

Conclusions: : Rabbit retinas submitted to intravitreal injections of Triesence® show morphological, as well as ERG changes. GFAP-positive processes were detected after 7 days, and disappeared after 30 days, suggestive of transient Muller cell activation. No signs of apoptosis or necrosis were observed even at the highest dose tested. The ERG results suggest retinal toxicity affecting the cone system with [4mg] and [8mg] (four or eight times the clinical dose). The drug also affects retinal mechanisms related to temporal processing at high frequencies.

Keywords: corticosteroids • retina • Muller cells