Low Vision

Low vision is a form of visual impairment that restricts daily activities and is not correctable with eye glasses, contact lenses, medicine, or surgery. There are approximately 161 million people with visual impairment in the world; it is believed that 124 million of these people have low vision. While low vision affects communities worldwide, the majority of those with untreated vision impairment live in developing countries. It is estimated that at least half of those with low vision could be assisted with devices such as magnifiers and telescopes, and specialized services such as mobility training.

Unfortunately, low vision is not well understood as a public health concept, and as a result, has not been successfully integrated into many healthcare systems. Without access to low-vision devices and services, individuals suffer from social exclusion and reduced quality of life. Families, communities, and society as a whole are deprived of the economic and humanitarian contributions of these individuals. The personal, social, and economic losses caused by low vision are unnecessary and preventable.

The International Statistical Classification of Diseases, Injuries, and Causes of Death describes visual impairment as an umbrella term encompassing blindness and low vision. The current medical definition of low vision is visual acuity of less than 6/18, but equal to or better than 3/60, or a corresponding visual field loss to less than 20 degrees in the better eye using best possible correction. In comparison, normal vision is defined as 20/20; blindness is defined as less than 3/60. Visual acuity is expressed as a fraction; the numerator is the number of feet between a person and a vision screening chart; the denominator is the distance at which a person with normal eyesight could clearly see the smallest characters on the chart. For example, a person with low vision has visual acuity of less than 6/18; they clearly see at six feet away what a person with normal vision is able to see at 18 feet away.

Low vision can be caused by macular degeneration, cataracts, corneal scarring, glaucoma, diabetic retinopathy, stroke, eye injury, or genetic conditions like albinism. There are three different types of low vision: loss of peripheral or side vision commonly caused by stroke or glaucoma, loss of central vision commonly caused by macular degeneration or macular/foveal hypoplasia in albinism, and general blurred vision commonly caused by cataracts, corneal scarring, or diabetic retinopathy. The National Eye Institute has identified some warning signs of low vision that may help people seek early treatment and diagnosis. With regular prescription eyeglasses, individuals with low vision may have difficulty recognizing familiar faces, doing things that require seeing clearly up close, such as reading, cooking, sewing, fixing things around the house, picking out colors, doing things at work or home because lights seem dimmer than they used to, or reading street and bus signs or the names of stores. Normal vision changes are natural; however, low vision is not a natural part of the aging process. It is recommended that adults have dilated eye exams at least every four years in their 20s, at least every four years in their 30s, every two years in their 40s, and annually starting at age 60. People with a family history of glaucoma, or those diagnosed with diabetes or HIV/AIDS should have dilated eye exams at least once a year.

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