The Role of Blood-Retinal Barrier in Retinal Neurodegenerative Diseases

Disruption of the blood-brain or blood-retinal barrier (BBB or BRB, respectively) is a common phenomenon in neurodegenerative diseases of the central nervous system. Although many existing reviews focus on the link between BBB disruption and neuronal degeneration in the brain, a similar analysis of the BRB integrity in retinal degeneration is currently unavailable. Like the BBB, the inner BRB is established by retinal blood vessels encapsulated in a neurovascular unit. The retinal neurovascular unit and BRB are affected not only in retina-specific neurodegenerative diseases (eg, diabetic retinopathy and retinitis pigmentosa) but also in neurodegenerative diseases that primarily affect the brain (eg, Alzheimer disease and Parkinson disease). In this review, the link between vascular abnormalities (including BRB disruption) and retinal neurodegeneration in these diseases will be discussed to highlight the pivotal role of BRB integrity in neuronal homeostasis and health.