A major long-term objective is to develop techniques for localizing the sites, and identifying the mechanisms of diseases of the retina and optic nerve. The multifocal electroretinogram (mERG) and visual evoked potential (mVEP) techniques are relatively new ways for measuring the physiological activity of local retinal and cortical activity. By studying the mERGs from patients with a variety of retinal/optic nerve problems we aim to develop a conceptual framework for relating changes in the mERG to sites and mechanisms of damage (aim 1a). In addition, some retinal diseases affect retinal mechanisms of adaptation and studies are designed to understand these changes. The mVEP technique is less developed and studies are proposed to improve this technology. These include the development of a method for measuring and specifying the strength of the signal in the mVEP response (aim 1b). Specific studies are proposed to understand the contribution of cone pathways to the mVEP, to assess repeat reliability, to optimize recording techniques, and to develop norms. The second long-term objective is to improve our understanding of the sites and mechanisms of particular diseases of the retina/optic nerve through studies employing behavioral (e.g. visual fields), structural (e.g. nerve fiber layer analysis) and electrophysiological techniques (e.g. mERG and mVEP). As part of aim 2, the mERG and visual field measures will be employed to better understand retinal damage in patients with retinitis pigmentosa and diabetic retinopathy and to assess possible damage following retinal surgery for macular holes and macular pucker. In addition, the sites and mechanisms of glaucomatous damage will be studied. These studies include a comparison of structural and functional measures to better understand the mechanism(s) of damage, an attempt to detect early damage, an assessment of the effect of acute decreases in intraocular pressure, and an assessment of whether there are selective deficits in the cone pathways. Finally, patients with acute optic neuritis will be followed with behavioral and mVEP techniques. An attempt will be made to understand the recovery o vision following optic neuritis (ON).