An individual shall also be considered to be blind for purposes of this title if he is blind as defined under a State plan approved under title X or XVI as in effect for October 1972 and received aid under such plan (on the basis of blindness) for December 1973, so long as he is continuously blind as so defined. Temporary vision impairment
Vision impairment for a few seconds, or minutes, may occur due to any of a variety of causes, some serious and requiring medical attention. Health effects
General functioning
Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of an individuals function. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if they have low visual demands. It is also important to note that best-corrected visual acuity differs from presenting visual acuity; a person with a "normal" best corrected acuity can have "poor" presenting acuity (e.g. individual who has uncorrected refractive error).
Cause
The most common causes of visual impairment globally in 2010 were:

Refractive error (42%)
Cataract  (33%)
Glaucoma (2%)
Age-related macular degeneration (1%)
Corneal opacification (1%)
Diabetic retinopathy (1%)
Childhood blindness
Trachoma (1%)
Undetermined (18%)The most common causes of blindness worldwide in 2010 were:

Cataracts (51%)
Glaucoma (8%)
Age-related macular degeneration (5%)
Corneal opacification (4%)
Childhood blindness (4%)
Refractive errors (3%)
Trachoma (3%)
Diabetic retinopathy (1%)
Undetermined (21%)About 90% of people who are visually impaired live in the developing world. Age-related macular degeneration, glaucoma, and diabetic retinopathy are the leading causes of blindness in the developed world.Among working-age adults who are newly blind in England and Wales the most common causes in 2010 were:
Hereditary retinal disorders (20.2%)
Diabetic retinopathy (14.4%)
Optic atrophy (14.1%)
Glaucoma (5.9%)
Congenital abnormalities (5.1%)
Disorders of the visual cortex (4.1%)
Cerebrovascular disease (3.2%)
Degeneration of the macula and posterior pole (3.0%)
Myopia (2.8%)
Corneal disorders (2.6%)
Malignant neoplasms of the brain and nervous system (1.5%)
Retinal detachment (1.4%)

Cataracts
Cataracts are the greying or opacity of the crystalline lens, which can be caused in children by intrauterine infections, metabolic disorders, and genetically transmitted syndromes. Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after the age of 40. Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and visual assistance.