blindness(redirected from Legally blind)
Also found in: Dictionary, Thesaurus, Encyclopedia.
See also: amblyopia, amaurosis.
blindness(1) Lack of visual perception due to structural or functional defects, which can occur anyplace from the eyelids to the visual cortex.
(2) An inability to perceive the parameters of a scene in the nominal visual field of a subject in the presence of adequate illumination.
blindnessAn inability to see effectively. See Blue color blindness, Legal blindness, Night blindness, Occupational blindness, Snowblindness, Transient monocular blindness.
See also: amblyopia, amaurosis
Blindness may be caused by diseases of the lens, retina, or other eye structures; diseases of the optic nerve; or lesions of the visual cortex or pathways of the brain. A small number of infants are born blind, but far more people become blind during life. In the U.S., blindness due to infection is rare, but worldwide diseases like trachoma and onchocerciasis are relatively common causes of severe visual impairment. In malnourished people, vitamin A deficiency is an important cause of blindness.
A variety of free services are available for the blind and physically handicapped. Talking Books Topics, published bimonthly in large-print, cassette, and disc formats, is distributed free to the blind and physically handicapped who participate in the Library of Congress free reading program. It lists recorded books and magazines available through a national network of cooperating libraries and provides news of developments and activities in library services. Subscription requests may be sent to Talking Books Topics, CMLS, P.O. Box 9150, Melbourne, FL 32902-9150.
amnesic color blindness
night blindnessNyctalopia (1).
red-green blindnessRed-green color blindness
red-green color blindness
river blindnessSee: onchocerciasis
solar blindnessEclipse blindness.
transient monocular blindness
In older adults, causes of carotid atherosclerosis include smoking, diabetes mellitus, hypertension, obesity, and hypercholesterolemia. When atherosclerotic plaques form within the carotid artery, they may ulcerate. The exposed endothelium within the artery becomes a focus of inflammation and blood clotting. Blindness occurs when tiny clots from the carotid arteries embolize to the ophthalmic arteries.
Patients often describe a dark shade descending into the field of vision. At the same time they may have other stroke symptoms, e.g., difficulty with speech or weakness of the hand on the side opposite the affected eye.
A patient who may have carotid atherosclerosis should begin taking aspirin or other antiplatelet drugs if these are tolerated. Blood pressure and lipid levels should be controlled. The patient should be referred for noninvasive evaluation of blood flow through the carotid arteries, e.g., ultrasonography. If the carotid arteries are significantly blocked, the patient and physician should consider the risks and benefits of carotid endarterectomy.
blue blindness See tritanopia.
colour blindness Sometimes this term is incorrectly used to cover all forms of colour vision deficiency, however mild or severe. See achromatopsia; defective colour vision; deuteranopia; monochromat; protanopia; tritanopia.
congenital stationary night blindness Night blindness (nyctalopia) inherited as either autosomal dominant with non-progressive nyctalopia but normal daylight visual acuity and visual fields and presumed to be due to a defect in neural transmission between the rods and the bipolars in the retina, or autosomal recessive or X-linked with congenital nyctalopia, myopia, nystagmus and reduced visual acuity. See Oguchi's disease; fundus albipunctatus; hemeralopia; retinitis pigmentosa.
cortical blindness Loss of vision due to lesions in the areas of both occipital lobes of the brain associated with visual functions. It may result from trauma or from a vascular disease (e.g. a circulatory occlusion caused by a stroke). A lesion in one occipital lobe may result in homonymous hemianopia, often with macular sparing.
day blindness See hemeralopia.
eclipse blindness Partial or complete loss of central vision due to a foveal lesion caused by fixating the sun without adequate eye protection. This condition is caused mainly by the infrared radiations from the sun. See actinic.
flash blindness See actinic keratoconjunctivitis.
green blindness See deuteranopia.
hysterical blindness Blindness associated with an emotional shock, which occurs without a physical or organic cause. The patient has normal blink and pupillary responses and the fundus appears normal. A placebo therapy and/or psychological counselling may be required.
legal blindness The definition varies from country to country. In the UK it is equal to either 3/60 (20/400) or worse; or 6/60 (20/200) or worse, with markedly restricted fields.
motion blindness A very rare condition in which a patient is unable to process information about motion, although other visual functions are unimpaired. This is believed to be the result of damage to the middle temporal cortex (V5). See visual association areas.
night blindness See hemeralopia.
perceptual blindness See agnosia.
red blindness See protanopia.
river blindness See onchocerciasis.
snow blindness See actinic keratoconjunctivitis.
word blindness See alexia.
Patient discussion about blindness
Q. Why is the color draining from my eyes?! When I was little I had rich shiny cobalt blue eyes! As I grew up they faded or just started to dim in color. Being partially blind you can see in my left eye the its a really light color and creamy instead of my deep blue color... Why does my eye color dim?! I didnt think going blind had anything to do with the color of my eyes changing... Or is it something else?! Please, and thank you!
are those the reason of your blindness?