ABSTRACT
Electrophysiologic tests such as pattern ERG and VEP are affected by optic neuropathies and in some cases may serve as useful objective clinical measures of dysfunction. For instance, residual deficits from recovered mild optic neuritis may be difficult to detect on ophthalmic examination or even with formal visual fields but may be detectable by pattern ERG or pattern VEP. However, these electrophysiologic tests require good fixation and are adjunctive clinical tests that should not be performed in isolation without a comprehensive ophthalmic examination with refraction. Novel electrophysiologic tests such as the multifocal VEP and optic nerve head component of the multifocal ERG are being developed to detect visual pathway dysfunction and their clinical utility requires further investigation. This chapter provides electrophysiologic information on optic neuropathies and central nervous system disorders. Nutritional optic neuropathy is discussed Chapter 15 along with other toxic and nutritional conditions. The outline of this chapter is as follows:
Optic neuropathies: Glaucoma Optic neuritis=multiple sclerosis Ischemic optic neuropathy Papilledema Compression of optic nerve or chiasm Traumatic optic neuropathy Optic nerve head drusen Hereditary optic neuropathies
Central nervous system disorders: Cortical blindness Spinocerebellar degeneration, olivopontocerebellar atrophy, and Friedreich ataxia
Alzheimer disease Parkinson disease Leukodystrophies
OPTIC NEUROPATHIES
Glaucoma
Glaucoma is a progressive optic neuropathy characterized by loss of retinal ganglion cells associated with increased cupping of the optic nerve head, progressive nerve-fiber-layer visual field defects, and usually, but not always, high intraocular pressure. There are many types of glaucoma with primary open-angle glaucoma being the most common. Glaucoma is one of the leading causes of blindness worldwide, and its prevalence increases with age. Patients with increased intraocular pressure without glaucomatous optic nerve and visual field damage are designated as having ‘‘ocular hypertension’’ and are at risk of developing glaucoma.
