The Effects of Hydrocephalus on the Retina and the Optic Nerve

Abstract

Papilledema is the swelling of the optic disc resulting from increased cranial pressure (ICP). A diagnosis of papilledema is important to not only treat pathologies of the eye, but it also can be an important indicator of underlying brain pathology since the subarachnoid space surrounding the optic nerve is contiguous with the brain. Therefore, the increased cranial pressure from brain pathology can be transmitted to the eye. Thus, it is important to have further understanding of the mechanism of papilledema and the anatomical and cellular changes that occur with sustained ICP. To study papilledema, a reproducible post hemorrhagic hydrocephalic (PHH) rat model was used to study the changes of the retina, optic disc, and optic nerve when exposed to high levels of ICP. Multiple retinal changes were noted in the PHH rats including decreased retinal thickness in the peripheral retina in female rats and increased retinal thickness close to the optic disc in male rats. PHH caused a decrease in ganglion cell layer thickness in the peripheral retina. In addition, vascular changes were noted with the PHH rats having an increased occurrence of enlarged retinal vasculature. In addition, the PHH rats had an increased optic disc width from analyzed retinal sections and increased optic disc diameter on optical coherence tomography (OCT). Also, PHH caused a decrease in retinal ganglion cells (RGC). These experiments confirm that PHH model in rats can produce retinal and optic disc phenotypes that are similar to those found in human pathology. Therefore, future studies are indicated utilizing the PHH rat model to provide further understanding of the mechanism of papilledema progression and to allow for the study of possible therapeutics.