Blindness (cont.)

The many causes of blindness differ according to the socioeconomic condition of the nation being studied. In developed nations, the leading causes of blindness include ocular complications of diabetes, macular degeneration, and traumatic injuries. In third-world nations where blindness is much more common and where about 85% of the world's blindness occurs, principal causes include infections, cataracts, glaucoma, injury, and inability to obtain any glasses.

Infectious causes in underdeveloped areas of the world include trachoma, onchocerciasis (river blindness), and leprosy. The most common infectious cause of blindness in developed nations is herpes simplex.

Other causes of blindness include vitamin A deficiency, retinopathy of prematurity, blood vessel disease involving the retina or optic nerve including stroke, ocular inflammatory disease, retinitis pigmentosa, primary or secondary malignancies of the eye, congenital abnormalities, hereditary diseases of the eye, and chemical poisoning from toxic agents such as methanol.

All people who are blind or have visual impairment have the common symptom of difficulty seeing. People with similar levels of visual loss may have very different responses to that symptom. If one is born blind, there is much less adjustment to a non-seeing world than there is for people who lose their vision late in life, where there may be limited ability to cope with that visual loss. Support systems available to individuals and their psychological makeup will also modify the symptom of lack of sight. People who lose their vision suddenly, rather than over a period of years, also can have more problems from their visual loss.

Associated symptoms, such a discomfort in the eyes, awareness of the eyes, foreign body sensation, and pain in the eyes or discharge from the eyes may be present or absent, depending on the underlying cause of the blindness.

A blind person may have no visible signs of any abnormalities when sitting in a chair and resting. When blindness is a result of infection of the cornea (the dome in front of the eye), the normally transparent cornea may become white. This opaque cornea can make it difficult to view the colored part of the eye. In blindness from cataract, the normally black pupil may appear white. Depending on the degree of blindness, the affected individual will exhibit signs of visual loss when attempting to ambulate. Some blind people have learned to look directly at a source of conversation.

Source: MedicineNet.com
http://www.medicinenet.com/blindness/article.htm