Pathobiology of the Outer Retina: Genetic and Nongenetic Causes of Disease

Abstract

The outer retina is composed primarily of rod and cone photoreceptor (PR) cells and retina pigment epithelial cells. These cells serve as the main cells of the retina and initiate the process of phototransduction whereby light is converted and transmitted to the visual cortex of the brain to generate an image. The majority of the diseases of the outer retina are genetic (over 97%) and result from mutations in genes associated with photoreceptor development, phototransduction, and maintenance of normal photoreceptor function. The retinal pigment epithelium (RPE) functions to nourish the PR cells and provides a mechanism to recycle photoreceptor outer segments that are spent during phototransduction. Thus, mutations in RPE genes also cause outer retinal degeneration. Further, a small percentage of outer retinal diseases result from trauma or injury to the retina. This article provides an overview of the pathobiology of outer retinal diseases. While each case is unique, the biological processes that are disrupted are common and thus a common pathology primarily of rod and cone degeneration leads to debilitating vision loss.