Visual Disturbances (Encyclopedia of Neurological Disorders)
Visual disturbances are abnormalities of sight. Visual disturbances associated with neurological disorders often include double vision (diplopia), moving or blurred vision due to nystagmus (involuntary rapid movements of the eyes), reduced visual acuity, reduced visual field, and partial or total loss of vision as in papilledema, a swelling of the optic disc, or in blindness. Visual disturbances are often symptoms of other disorders, in particular neurological disorders, but can also occur due to muscular disorders, vascular diseases, cancer, or trauma. Additionally, diseases such as diabetes and hyperthyroidism can contribute to the visual abnormalities. Some visual disturbances arise from congenital conditions that are often hereditary.
Diplopia, or double vision, causes a person to see two objects instead of one. There are two main reasons for diplopia: one is a physical change in the lens, conjuctiva, or retinal surface; the second reason involves an inability of the brain to overlay the images seen with both eyes, which happens in a person with normal vision. The first type usually involves only one eye and is not corrected by covering of the eye. Scars or other physical defects in the eye cause the split of a single image, thus resulting in double vision. In contrast,...
(The entire section is 1615 words.)
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