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Blindness.
Blindness is the absence of vision in one or both eyes. It may be present at birth, or it may occur suddenly in one or both eyes at a later stage in life. Commonly blindness involves a gradual deterioration of vision until the stage when no sight remains. It may be caused by various disorders affecting the eye itself or may result from a disorder of the visual center of the brain. The medical term for blindness in which the eye appears to be normal is amaurosis. Temporary blindness, commonly called a blackout, can occur with some minor disorders, such as fainting.
INTRODUCTION OF BLINDESS
Blindness in the loss of normal or correctable vision. It can be partial, with loss of only part of the vision. It can also be complete, in which case there is no perception of light. People worse than 20/200 vision are considered legally blind.
Blindness has many causes, yet the incidence of true blindness in the United States remains low. Accidents, diabetes, and macular degeneration account for most blindness in the United States. Worldwide, vitamin A deficiency is the leading cause of blindness.The common causes of blindness are: accidental trauma to the eyes (such as chemical burns, or injuries from bungiecords, fishing hooks, racket ball, fireworks, and similar objects); diabetes; vitamin A deficiency; basal cell nevus syndrome;
Tay-Sachs disease; retinitis pigmentosa; retinoblastoma.There are other causes of blindness. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on ageand gender of the affected person, as well as on the specific characteristics of thesymptom such as quality, time course, aggravating factors, relieving factors, andassociated complaints. Use the Symptom Analysis option to explore the possible explanations for blindness, occurring alone or in combination with other problems.
Q:Why are some babies born blind?A: Congenital blindness is sometimes caused by infection of the mother by rubella (German measles) at some time during the first three months of pregnancy. The disease causes the lenses in the baby's eyes to be opaque. Other causes of congenital blindness are defects in the formation of the eye and various metabolic disorders.
Q:What are the causes of gradual blindness?
A: Any of the following disorders may cause gradual blindness: pressure within the eyeball(glaucoma); the formation of opaque patches in the eye lens (cataract); a retina damaged as a result of high blood pressure (hypertension), diabetes, or degenerative disease of the retina; pressure on the optic nerve from a tumor (for example, pituitary gland adenoma); or recurrent ulcers on the cornea, which may be caused by a form of conjunctivitis (trachoma) common in hot, dry climates. Treatment of the cause usually arrests the condition and, in some cases, may restore sight.
Q:What causes sudden blindness?
A: The retina, the part of the eye onto which light rays are focused, may become detached from the layer enclosing it (the choroid), and blindness can result. Detached retina may be caused by an accidental blow to the eye, or it may occur spontaneously in people with the vision defect myopia (nearsightedness). Bleeding behind the retina or inflammation of the optic nerve (retrobulbar neuritis) may cause blindness in one eye. A blocked vein or artery supplying the eye can also result in sudden blindness. Sudden blindness in one eye occurs much more frequently than sudden blindness in both.
Q:What causes temporary blindness?
A: Temporary blindness may be caused by a spasm of the arteries during a bad migraine headache, by low blood pressure that precedes fainting, or by a small blood clot (embolus) that is passing through an artery that serves the eye.
Q:How can a person adapt to being blind?
A: Many schools and agencies provide education and training for people who are born blind or become blind later in life. Blind persons learn to use Braille and other techniques to help them retain their independence. Blind persons are employed in practically every profession, including computer programming, engineering, law, music, teaching, and many other fields.
