Neuronal Degeneration in the Retina during Ageing and in Neurodegeneration

CNS neurons gradually tend to dysfunction and degenerate with increasing age. This process may to some extent be conceived as part of the physiological ageing process, and it does not necessarily lead to relevant functional impairment. Excessive, pathological neuronal degeneration, as occurs in sporadic neurodegenerative diseases such as Alzheimer's disease, may represent premature ageing and degeneration of neurons in particular brain regions and functional circuits. Alzheimer's disease is characterized by progressive dysfunction and synaptic as well as neuronal loss of cholinergic neurons in the basal forebrain, cortex, and hippocampus. Deposition of amyloid plaques and the presence of dystrophic neurites are the main histological hallmarks of the disease. The retina is not considered a major site of Alzheimer's disease pathology. However, there are several hints towards involvement of the visual system in Alzheimer's disease. Here, we will first discuss the evidence of retinal changes with age. Then, clinical evidence for pathology in the retina and optic pathway in Alzheimer's disease will be presented. Finally, we will discuss potential retinal pathology in genetic mouse models of Alzheimer's disease.