NEURODEGENERATION AND THE RETINA: Neurode-

generation is a collective term for the progressive loss of the structure, function, or even death of neurons. The pathogen-esis of neurodegeneration involves the aberrant processing, misfolding, and subsequent aggregation of normal proteins that are then deposited both intracellularly and extracellu-larly. At the molecular level, it involves mechanisms such as defective neuronal plasticity through aberrant regenerative responses, reduced levels of neurotrophins, and increased neuronal vulnerability to stress. At least three types of abnormally aggregated proteins have been found. These include β-amyloid (Aβ) peptides in the neuritic plaques of Alzheimer’s disease (AD), the fibrillation of tau protein to form neurofibrillary tangles in AD and Pick bodies in fron-totemporal dementia (FTD), and alpha-synuclein in the Lewy bodies of Parkinson disease (PD) and in Lewy body diseas