Neuroprotective effects of intravitreal triamcinolone acetonide and dexamethasone implant in rabbit retinas after pars plana vitrectomy and silicone oil injection.

ABSTRACT

PURPOSE: To investigate potential retinal neuroprotective effects of intravitreal triamcinolone acetonide and dexamethasone implant in rabbits after pars plana vitrectomy and intravitreal silicone oil injection. METHODS: The right eyes of 84 rabbits, divided into 3 groups of 28 rabbits each, underwent standard 3-port pars plana vitrectomy with silicone oil (SO group), silicone oil and intravitreal dexamethasone implant (SO/DEX group), or silicone oil and triamcinolone acetonide (SO/TA group). The retina from the left eye of each rabbit served as a control. The animals were killed at 4 weeks after surgery. Qualitative and quantitative histopathologic analyses were performed 4 weeks after surgery, and investigation for apoptosis was performed using the Tunel assay. RESULTS: Intravitreal triamcinolone acetonide and dexamethasone implant were associated with increased retinal neuronal survival, primarily in the outer nuclear layer, inner nuclear layer, and ganglion cell layer. In the SO group, the cell density in eyes that underwent PPV/SO was 31% lower in the outer nuclear layer, 33% lower in the inner nuclear layer, and 45% lower in the ganglion cell layer compared to control eyes (p < 0.05 for all PPV/SO versus control comparisons). Compared to eyes that underwent PPV/SO, the cell density in eyes treated with triamcinolone was 27% higher in the outer nuclear layer, 66% higher in the inner nuclear layer, and 100% higher in the ganglion cell layer (p < 0.05 for all triamcinolone versus PPV/SO comparisons). Compared to eyes that underwent PPV/SO, the cell density in eyes treated with dexamethasone was 46% higher in the outer nuclear layer, 62% higher in the inner nuclear layer, and 77% higher in the ganglion cell layer (p < 0.05 for all dexamethasone versus PPV/SO comparisons). Analyses using the Tunnel assay demonstrated apoptotic bodies in all eyes in the SO group, compared with none of the eyes in the SO/TA and SO/DEX groups. The presence of cell nuclei stained with 49,6-diamidino-2-phenylindole (DAPI) was demonstrated in all groups. CONCLUSION: In this experimental model of neuroprotection, increased retinal neuronal survival was seen in the steroid-treated groups compared with the controls.