How common is vision impairment?

Photo of child with vision impairment drawing on an easelVision impairment is not very common among children. To learn just how common it is, CDC is tracking the number of children with vision impairment in a five-county area in metropolitan Atlanta, Georgia. This activity is part of the Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP). In 1996, an estimated 1.4 per 1,000 8-year-olds in metro Atlanta, or about 1 in 715, had vision impairment. In 2000, the prevalence was an estimated 1.2 per 1,000, or about 1 in 833, 8-year-olds. About one half (2000) to two thirds (1996) of children with vision impairment also had one or more other developmental disabilities tracked by MADDSP.
CDC also studied how many children in metropolitan Atlanta were legally blind in the mid-1980s. This project was done as part of the Metropolitan Atlanta Developmental Disabilities Study (MADDS), which studied how common certain disabilities were in 10-year-old children. We found that nearly 7 of every 10,000 children 10 years of age had legal blindness. Two-thirds of the children also had another disability, such as mental retardation, cerebral palsy, or epilepsy.

Vision impairment is more common in older people than in children.. A 2002 report by the National Eye Institute and Prevent Blindness America estimates that more than 1 million people ages 40 years or older in the United States are blind (best corrected visual acuity of 20/200 or worse or a visual field of less than 20 degrees). Another 2.4 million are visually impaired (best corrected visual acuity of 20/40 or worse). The report states that the number of adults with vision impairment likely will double over the next 30 years.

What causes vision impairment? Can it be prevented?

Vision impairment can be caused by damage to the eye itself that affects its ability to receive or process visual information. Impairment can also be due to the eye being shaped incorrectly, which can make it harder to focus on things. Vision impairment can also occur if the brain does not process visual information correctly. Vision impairment can occur anytime during a person’s life, even before birth.

CDC studied the causes of low vision and blindness in 3- to 10-year old children in metropolitan Atlanta, Georgia. We found that most of the causes happened before the child was born or before they were 1 month old. The most common cause was retinopathy of prematurity (ROP), which refers to abnormal blood vessel growth or scarring of the retina of the eye. Children who are born very early or who have very low birth weight are most at risk of having this condition. ROP usually gets better on its own before severe damage can occur, and if not, it can often be treated. However, a small percentage of children with ROP have a severe form and will have low vision or blindness. Other common causes of vision impairment found in the CDC study were albinism (a genetic condition that results in decreased skin pigmentation and affects parts of the eye), hydrocephalus (a condition in which there is too much fluid in the brain), congenital cytomegalovirus (a viral infection that occurs before a baby is born), and birth asphyxia (where a baby does not get enough oxygen before or during birth).

The most common causes of vision impairment among adults in the United States are diabetic retinopathy, age-related macular degeneration, cataracts, and glaucoma. Diabetic retinopathy is a common complication of diabetes in which the blood vessels in the retina break down, leak, or become blocked, leading to vision impairment. Age-related macular degeneration affects the part of the retina that is responsible for sharp central vision. Cataracts are a clouding of the eye’s lens, which is normally clear. Glaucoma is increased fluid and pressure within the eye that leads to enlargement of the eyeball. The risk of vision loss from many of these conditions can often be reduced if the condition is found early and treated.

If you would like to learn more about a specific genetic condition that you think could cause vision impairment, you can go to the National Library of Medicine’s Genetics Home Reference Web site. Information on each genetic condition includes symptoms, how common it is, related genes, treatments, and links to resources where you can learn more about the condition. The Genetics Home Reference also can help you learn more about genetics, including genetic testing, genetic counseling, and gene therapy.

You can search for CDC guidelines on preventing vision impairment by visiting the “CDC Recommends: The Prevention Guidelines System” Web site. The guidelines include information about vision problems caused by diabetes, infections, eye injuries caused by fireworks, and other topics.

Healthy People 2010 is a national effort to promote health and prevent disease. It includes goals related to vision impairment, such as preventing eye injuries, increasing the number of people who have their eyes examined, decreasing the number of children under 17 years old who are blind or visually impaired, decreasing the number of people who lose their vision due to diabetes, and others. The National Eye Institute (NEI) has created a Web site named “Healthy Vision 2010″ that provides more information about the vision-related goals in Healthy People 2010.

Full article and more information at: http://www.cdc.gov/ncbddd/dd/ddvi.htm