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 (PPV) and intravitreal silicone oil injection.

Methods: The right eyes of 84 rabbits (divided into three groups of 28 rabbits each) underwent standard three-port PPV with intravitreal silicone oil injection (SO group), silicone oil and intravitreal triamcinolone acetonide injection (SO/TA group), or silicone oil and intravitreal dexamethasone implant placement (SO/DEX group ). The retina from the left eye of each rabbit served as a control. The animals were euthanized at 4 weeks after surgery. Qualitative and quantitative histopathological 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 significantly increased retinal neuronal survival, primarily in the outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL). At 4 weeks postoperatively, the mean cell density in the SO group compared to control eyes was 31% lower in the ONL, 33% in the INL, and 45% lower in the GCL (p<0.001). The mean cell density in the SO/TA group compared to the SO group was 27% higher in the ONL, 66% higher in the INL, and 100% higher in the GCL (p<0.01). The mean cell density in the SO/DEX group compared to the SO group was 46% higher in the ONL, 62% higher in the INL, and 77% higher in the GCL (p<0.,001). 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 4',6-diamidino-2-phenylindole(DAPI) was demonstrated in all groups.

Conclusions: Intravitreal triamcinolone injection and intravitreal dexamethasone implant placement are associated with neuroprotective effects in eyes undergoing PPV with silicone oil injection.

Keywords: 615 neuroprotection • 764 vitreous substitutes • 503 drug toxicity/drug effects