Immunocytochemical characterization of cysts in the peripheral retina and pars plana of the adult primate

PURPOSE. To better characterize the cellular constituents of cysts in the p eripheral retina and pars plana of the adult monkey. METHODS. Frozen sections of the peripheral retinal margin and pars plana fr om monkeys (Macaca nemestrina) between 1 and 15 years of age were stained w ith toluidine blue or immunolabeled with a variety of glia- and neuron-spec ific antibodies. RESULTS. In animals 1 to 2 years of age, the nonpigmented inner layer of th e pars plana is a pseudostratified columnar epithelium. In these young anim als, the peripheral retina had distinct layers and did not contain cysts. I n animals 6 years of age or older, there were numerous cysts in the pars pl ana and in the peripheral retina. In the peripheral retina, neurons were ra ndomly distributed and did not have a laminar organization. Cells surroundi ng cysts were immunoreactive for different types of markers for retinal neu rons. Some of the cells surrounding cysts in the pars plana were also unexp ectedly immunoreactive for antigens normally expressed only in retinal neur ons and glia. CONCLUSIONS. Cysts form in the peripheral retina and pars plana in adult mo nkeys. The peripheral retinal cysts disrupt the normal lamination of the ce lls, but all types of retinal neurons are still present in the cysts. In an unexpected finding, cysts in the pars plana also contained cells immunorea ctive for a few of the markers of retinal cells, suggesting that neurogenes is may occur in the pars plana of the adult primate.