Retinal Function Analysis and Histopathologic Assessment after Intravitreal Cidofovir Injection in Normal Beagle Dogs

This study was performed to evaluate the effects of an intravitreal injection of cidofovir in beagle dogs. Nine beagle dogs (18 eyes) were used and randomly assigned to the following three groups of various dosages: 100, 500 and $1000{\mu}g$. Aqueous paracentesis was followed by an intravitreal injection of cidofovir. Intraocular pressure (IOP) was measured twice a week and electroretinography (ERG) and ophthalmoscopic examination were performed every week during the study. At the end of the study, all eyes were enucleated for histopathologic evaluation after euthanasia. The IOPs in the 500 and $1000{\mu}g$ groups were statistically lower than baseline with no significant IOP changes in the $100{\mu}g$ group. Reduced amplitudes of ERG recordings were identified in the eyes injected with higher dose groups than the $100{\mu}g$ group. Histopathologic examination revealed that there were dose-related toxicities to the ciliary body and the retina. These results suggest that intravitreal cidofovir had dose-dependent IOP lowering effects associated with ciliary body destruction, but had the potential to cause retinal toxicity in beagle dogs.