Demographics of vision loss in the United States: dealing with definitions.
DEFINITIONS DETERMINE EVERYTHING
Because there is not one definitive statistic from a single source that accounts for everyone with vision loss in the United States, it is important that those seeking information about vision loss, as well as those providing answers, first understand that there are several definitions of vision loss to choose from among the various national household surveys.
Whenever questions about demographic statistics about people with visual impairment or blindness come to the American Foundation for the Blind (AFB), the first step in answering such questions is to understand precisely which group of visually impaired people the questioner is interested in. The answer to this question determines whether the response offers statistics on the number of people with blindness, severe visual impairment, or low vision. The surveys that track people with vision loss in the United States define visual impairment in the following ways.
The most recent National Health Interview Survey (NHIS), published in 2008, defines individuals with vision loss as those who reported that they have trouble seeing, even when wearing eyeglasses or contact lenses. Included in this broad definition are individuals who reported that they are blind or unable to see at all, and no visual acuity cutoff is provided.
The 1994-1995 National Health Interview Survey on Disability (NHIS-D) defines individuals who are legally blind as those who reported that they have a central visual acuity of 20/200 or less in the better eye with the best possible correction or a visual field of 20 degrees or less. The definition used by NHIS-D is unique, because there has not been another national survey that explicitly assessed the number of Americans who are legally blind since NHIS-D was conducted in the mid-1990s.
The 2008 American Community Survey (ACS) defines people who have difficulty seeing as those who reported blindness or serious difficulty seeing even when wearing eyeglasses. This definition of vision loss will be used in all ACS data collection from 2008 forward. In the 2001 through 2007 ACS data collection years, blindness, deafness, or severe vision or hearing impairment were all defined together to identify people with self-reported sensory impairments. During these years, ACS data could not be used to assess the characteristics of people who have serious difficulty seeing separately from the characteristics of people with other sensory disabilities.
The Department of Labor's Bureau of Labor Statistics (BLS) uses its Current Population Survey (CPS) to report monthly employment data about people with disabilities. People with vision loss were identified by the CPS if they reported that they or someone in their household is blind or has serious difficulty seeing when wearing eyeglasses. This definition is identical to the definition used in the most recent ACS.
The Survey of Income and Employment Participation (SIPP) defines people who have trouble seeing as individuals who normally wear eyeglasses and reported difficulty reading small print in a newspapers even when wearing their eyeglasses.
As these particular examples illustrate, the definitions of vision loss vary widely as used by the population surveys conducted in the United States. The definition and scope of what it means to have vision loss make a big difference in the size and magnitude of the estimate, as do any other limitations of the particular data source. Because the use of statistics of people with visual impairment is most accurate when the specific definitions of vision loss used by the surveys are taken into account, investigators are urged to pay close attention to the definition of vision loss applied to each estimate. This stipulation cannot be overlooked when seeking or providing demographic information about people with vision loss.
Stacy M. Kelly, Ed.D., COMS, Public Policy Center, American Foundation for the Blind, 1660 L Street Northwest, Suite 513, Washington, DC 20036; e-mail: <email@example.com>.
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|Title Annotation:||Statistical Snapshots|
|Author:||Kelly, Stacy M.|
|Publication:||Journal of Visual Impairment & Blindness|
|Date:||Mar 1, 2009|
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