Routes of viral spread in the von Szily model of herpes simplex virus retinopathy.

Intraocular inoculation of herpes simplex virus type 1 (HSV-1) in one eye of rabbits results in encephalitis and contralateral necrotizing viral retinopathy. The effects of viral inoculation site and optic nerve (ON) transection on the spread of virus to the brain and contralateral eye in this model were investigated. A surgical technique was developed for transection of the retrobulbar optic nerve posterior to the entrance of the central retinal vessels. HSV-1 was inoculated into the AC or vitreous of one eye in normal rabbits and in rabbits with one ON transected, either ipsilateral or contralateral to the side of inoculation. Animals were followed clinically for signs of disease. Encephalitis and contralateral retinopathy (CR) occurred following both AC and vitreous inoculation of virus, although CR developed later in AC-inoculated rabbits. Ipsilateral retinopathy (IR) developed in 83% of vitreous-inoculated rabbits, but in only 5% of AC-inoculated animals. IR developed 8 days after the onset of CR in the AC-inoculated group. ON transection on the side of virus inoculation prevented development of CR only in vitreous-inoculated rabbits. ON transection on the side opposite virus inoculation prevented CR regardless of the site of inoculation. These findings suggest that HSV-1 can leave the inoculated eye by multiple routes depending on the site of virus inoculation, but that virus reaches the retina of the contralateral eye via the optic nerve.