Research Navigator: Just how many blind folks are there anyway?
Population and Demographic Statistics for Adults who are Blind or Visually Impaired
What to look for in this edition of the Navigator:
- Numbers, numbers, numbers! We explore and explain the range of data and data sources related to blindness and visual impairment.
- Why does AFB frequently cite the statistic of 21 million American adults with vision loss? Learn where this number comes from and who it describes. We discuss selecting the correct data source to answer a variety of research, policy, and advocacy questions.
- Work is underway to establish a national vision surveillance system, which will help to address some of the vision loss data scarcity and confusion. Dr. John Crews from the Centers for Disease Control and Prevention, an expert in vision surveillance and a key figure in the development of the new surveillance system, will be presenting at AFB’s upcoming Leadership Conference. We encourage you to attend and engage with Dr. Crews about priorities for data collection.
- AFB and the U.S. Census Bureau will be presenting a new webinar series on vision loss statistics, including tools and strategies for accessing national data sets to answer a variety of important questions.
About this Series
Welcome to the second edition of AFB’s Research Navigator. This is a quarterly series of the AFB Public Policy Center. The purpose of this series is to keep you informed of user-friendly facts and figures and the latest research pertaining to people with vision loss. The series will also include the necessary background information so you may use the information most accurately. Readers are also encouraged to check out AFB’s Statistical Snapshots on a regular basis. This webpage is regularly updated with a wide variety of information and tools that address commonly asked questions about people with vision loss.
Introduction to the Topic
When you think about research and statistics related to blindness and visual impairment, what are some of the first questions that come to mind? For many people, essential questions include “How many people are blind?”; “How many men or how many women are visually impaired?”; “What ages?”; “Where do they live?”
These questions are answered by a particular type of data known as demographics. Demography is “the study of variables characterizing human population (such as births, deaths, health, fertility, and migration)” (Vogt & Johnson, 2011, p. 102), and demographics are these particular variables, including sex/gender, age, disability status, etc., often reported as totals or averages for a group of people. Demographic data about a population are the backbone of any study or statistical report; likewise, for anyone applying for support (such as a federal grant) for a program or research study, current statistics about the population are an important part of describing the need and rationale for funding. Researchers, the media, politicians, and the general public often turn to national surveys (such as the Census) for current and reliable estimates of demographic information, and AFB plays a role by gathering and sharing the latest demographic statistics from multiple national surveys on our Statistical Snapshots webpages.
In the field of blindness and visual impairment, we encounter a host of challenges ascertaining basic demographics and statistics at all levels – global, national, state, and local. The most complicating factor in describing any population of people who are blind or visually impaired is the lack of a consistent, clear, and useful definition of visual impairment. This edition of the Research Navigator discusses various sources of national demographic data about adults with vision loss and will explore reasons for discrepancies between data sources. (We will be following up shortly with an additional edition of the Navigator focusing specifically on infants, children, and young adults.) We conclude the current edition by announcing special opportunities to become involved in the future of data collection through AFB’s Leadership Conference as well an upcoming, free webinar series for those who wish to learn methods and tools for accessing national population data related to vision loss.
National Population Statistics
No single survey instrument asks every person in the U.S. about his/her vision. Most reports of national-level data are based on samples of people which are selected to be random while also representing the larger population. Mathematical calculations, called weightings, are used to estimate population parameters based upon the sample statistics. Reports from these surveys generally include margins of error, reflecting the precision of the estimates (larger sample sizes generally lead to smaller margins of error).
For example, the frequently cited estimate of 21 million adults in the U.S. with vision loss comes from the National Health Interview Survey (NHIS) (Centers for Disease Control, 2014). The NHIS is conducted by the Centers for Disease Control and Prevention and includes self-reported data from a sample of people in the civilian, noninstitutionalized population. In this context, noninstitutionalized means that the survey excludes people who live in long-term care facilities or who are incarcerated. The NHIS frequently reports separate data for children (under age 18) and adults (18 years and over). The NHIS variable “has trouble seeing” refers to individuals who respond “yes” to the question “Do you have trouble seeing, even when wearing glasses or contact lenses?” Respondents are also included if they respond “yes” to a second question, “Are you blind or unable to see at all?” In 2013, the NHIS had a sample size of 104,520 adults, 3,512 of whom reported having trouble seeing. Based on their weighting calculations, they estimated that 21,481,688 civilian, noninstitutionalized, adult Americans have trouble seeing (9% of the adult population, +/- 0.35%) (National Center for Health Statistics, 2015). Of course this estimation (and all other population data cited in this edition of the Navigator) does not differentiate people who have additional disabilities from people whose only disability is visual impairment. Since the NHIS also collects a range of demographic information from participants (age, sex, etc.), they are also able to provide estimates for vision loss in population subgroups, including intersections of vision loss with other disabilities.
Since the NHIS is updated yearly, like most national surveys, we can use its data to track changes and trends in the population over time. For example, the NHIS estimate of American adults with vision loss has varied from year-to-year, hovering around 21 million:
- 2012 estimate: 20.6 million
- 2011 estimate: 21.2 million
- 2010 estimate: 21.5 million
- 2009 estimate: 19.4 million
- 2008 estimate: 25.2 million
- 2007 estimate: 22.4 million
- 2006 estimate: 21.2 million
(See AFB's Statistical Snapshots on Adults with Vision Loss for more NHIS data from 2006-2013). It is unlikely that the actual population of people with vision loss is changing each year by as much as 5 million people; rather factors such as the way that the data are collected may impact the differences in totals from year to year. A future edition of the Research Navigator will discuss longitudinal data in more detail.
Another important national survey is the American Community Survey (ACS), run by the Census Bureau. While the decennial national census does attempt to count every American, the American Community Survey is conducted throughout the year, every year, and helps to measure additional features of the total population through detailed questioning of smaller samples. The ACS is mailed to approximately 295,000 addresses every month and follows up with telephone surveys and personal visits as needed (U.S. Census Bureau, 2015). The Census Bureau publishes estimated population parameters based on 1-year, 3-year, and 5-year collections of sample data. 1-year data are valuable when researchers want up-to-date statistics or want to study year- to-year changes and trends; however, 5-year estimates are based upon five times larger sample sizes and are therefore able to estimate population data more precisely (especially for smaller subgroups like people with vision loss in a particular zip code). With respect to vision loss, the ACS includes the variable “vision difficulty” (every year), which is based upon responses the question, “Is this person blind, or does he/she have serious difficulty seeing, even when wearing contacts or glasses?” The 2013, 1-year ACS data leads to an estimate that 6,753,573 adults (18 and over) have vision difficulty (2.8% of the adult population, +/- 0.1%) (U.S. Census Bureau, 2015b).
Why the huge difference between NHIS and ACS estimates of vision loss among American adults? An important difference between the surveys lies in the question used to define each survey’s vision loss variable. The NHIS asks participants first if they have trouble seeing, then – in a separate, second question – asks if they are blind or if they cannot see at all. However, the ACS asks a single question, beginning with the term blindness: “is this person blind, or does he/she have serious difficulty seeing…” Participants may perceive the NHIS definition of vision loss more broadly, and ACS participants may be less inclined to identify with the concepts “blind” and/or “serious difficulty seeing.”
Matching the Data Source to the Question
Given that two different sources of data can provide widely differing answers to what seems to be the same question, how can we decide which numbers to use in which situation? One option (popular in the policy arena) is to choose the number which suits your purposes. Certainly, when advocating for services that could be useful to anyone with some level of vision loss, we are inclined to use the NHIS data, with the most inclusive interpretation of “vision trouble.” For example, video description provides access to video content for anyone who has trouble seeing a television screen; therefore, when AFB is asked "How many Americans are impacted by legal requirements for video description?," we respond with the NHIS estimate of "over 21 million." Additional data sources may be most helpful for other purposes:
Legal blindness is a level of vision loss that has been legally defined to determine eligibility for benefits, such as Social Security and/or Social Security Disability Insurance (download a PDF about Social Security Benefits for people who are blind/have low vision). The clinical diagnosis of legal blindness refers to a central visual acuity of 20/200 or less in the better eye with the best possible correction, and/or a visual field of 20 degrees or less. Often, people who are diagnosed with legal blindness still have some useable vision. If you are interested in knowing the number of people likely to be eligible for a certain benefit program, then knowing the number of people who are legally blind may be useful.
Following the signing of the Americans with Disabilities Act in 1990, in 1994 and 1995, the National Health Interview Survey included a supplemental survey on disability (NHIS-D). Data from this survey should be used with caution today, given that they are over 20 years old. AFB used this data, when it was released, to report on differences in employment rates between people who were legally blind versus the larger population of people with vision loss. The NHIS-D estimated that there were 345,000 legally blind adults of working age (18-54), roughly 21% of working-age people with “serious vision loss” (note that NHIS-D’s definition of vision loss in 1994-1995 is different from the current NHIS definition). The NHIS-D also estimated that the total population of legally blind, non-institutionalized adults ages 18 and over was 994,000 (Zuckerman, 2004). Again, when citing this data, researchers should note that the NHIS-D has not been repeated since 1995.
Another set of data on legal blindness comes from an unusual source – the Internal Revenue Service (IRS). Like the Social Security Administration, the IRS uses the definition of legal blindness as an eligibility criterion for a higher standard deduction on federal income taxes. If you are blind on the last day of the year and you do not itemize deductions on your return, you are entitled to a higher standard deduction. If you are not totally blind, you must obtain a certified statement from an eye doctor (ophthalmologist or optometrist) that you are legally blind. (AFB recommends you consult your tax advisor for more information). The IRS’s publication, Individual Income Tax Return, Line Item Estimates shows the number of returns populating various lines on the Individual Forms and Schedules, including the number of income tax returns where people check a box indicating that they are themselves blind or that their spouse is blind (download a PDF of the 2012 document). In 2012, 282,063 people indicated that they were legally blind, and 102,912 people indicated that their spouse was legally blind, for a total of 384,975 people. However, this number cannot be considered representative of all blind people in the United States as some people are not required to file income taxes (depending on income, age, and filing status), and there is no requirement that someone must disclose his/her blindness on an income tax form. Additionally, some people who qualify for this higher standard deduction may be unaware of the opportunity for a higher deduction and/or unaware that they meet the definition of legal blindness.
Specific Eye Conditions
In some cases, researchers and advocates need population data about people with specific eye conditions or groups of eye conditions (such as age-related vision loss). The inherent problem with collecting this type of data is that many people who have eye conditions do not know that they have them, and even if they do know they are experiencing vision loss, they may not know the name of the condition. For this reason, studying specific causes of disease (a science known as etiology) usually relies on data gathered from medical professionals.
For prevalence rates of specific eye conditions, the World Health Organization often provides informative estimates for the global population (for example, see Resnikoff et al., 2004). The best data sources for the U.S. population are individual eye studies, often reported in research journals, and larger research projects which combine data from several studies.
The organization Prevent Blindness America, in partnership with the National Eye Institute, conducted a study called Vision Problems in the U.S. For this study, researchers collected data from a variety of existing eye studies, mathematically combined and adjusted the data based on national population statistics, and then reported on “the prevalence of sight-threatening eye diseases in Americans age 40 and older,” including the prevalence of blindness and visual impairment and significant refractive error. They estimate that there are 2,907,000 Americans over age 40 with visual impairment, or about 2% of the 40+ population. Note that this is significantly smaller than the ACS estimate of 6,134,000 Americans ages 40 and up with vision loss. This difference is due in part to the fact that Prevent Blindness’s data comes from eye studies (derived from data collected in physician’s offices), while the ACS is a national survey in which vision loss can be self-reported. Knowing the characteristics of the Prevent Blindness data is important when interpreting their eye-disease-specific data as well. See the full Vision Problems in the U.S. report, including estimated cases of age-related macular degeneration, cataracts, diabetic retinopathy, and glaucoma.
The Future of Data and Statistics for Americans with Vision Loss
In 2012, as part of a special supplement to the Journal of Ophthalmology following a Center for Disease Control and Prevention panel on vision surveillance, Crews et al. wrote, “The Variability of Vision Loss Assessment in Federally Sponsored Surveys: Seeking Conceptual Clarity and Comparability.” The authors described the range of questions about vision from a dozen large surveys – including the ACS and NHIS. They found over 100 different ways in which vision was measured in the various surveys and concluded that the range of questions and the lack of consistent questions across surveys “resulted in an inability to consistently characterize the population of people experiencing visual impairment” (p. S31). Crews et al. recommended working towards more consistent language for vision questions in surveys.
In the same edition of the Journal of Ophthalmology as Crews et al. (2012), an editorial by West and Lee proposed the usefulness of a national vision surveillance system in the United States. They advocated, “A true surveillance system is an active, dynamic process that feeds data to end users who can effect change in policy and programs” (2012, p. S2). (Download these and other articles from the journal supplement from the CDC). Subsequently, in November of 2014, the CDC released a Funding Opportunity for a $1 million grant to “Establish a Vision and Eye Health Surveillance System for the Nation.” Applications for this opportunity are due February 5, 2015, and once a proposal is selected and funded, work will begin to fulfill this important task.
While the ACS and NHIS will continue to be valuable resources for data on vision loss in the United States, and additional resources like the Vision Problems in the U.S. study will provide insight on specific subpopulations, we look forward to the depth and breadth of information that will come from an ongoing surveillance system focused specifically on vision. AFB encourages stakeholders in the field of visual impairment to follow the funding and development of this system and to provide feedback to the CDC about the language and types of questions used to collect data. Dr. John Crews, Health Scientist with the Vision Health Initiative of the National Center for Chronic Disease Prevention and Health Promotion, (and panel member and lead author in the previously mentioned work on vision surveillance) will be participating in AFB’s Leadership Conference in Phoenix and is eager to hear from the field about the types of data which are most relevant in areas of special education, rehabilitation, and beyond.
Want to Learn More?
In addition to attending AFB’s Leadership Conference, where you can participate in sessions specifically addressing research priorities for the field of blindness and visual impairment, we encourage anyone with an interest in demographics and population characteristics to participate in an upcoming series of webinars being offered collaboratively by AFB and the U.S. Census Bureau. These webinars will cover a range of online researcher tools for accessing data from the ACS and NHIS and will include important information about definitions and comparability of data sets. The first webinar (Measuring America: An Overview on Vision Disability Statistics) will take place at 2:00 pm Eastern time on February 26th, 2015. A recording of the webinar will be posted online at a later date. Please email Rebecca Sheffield, AFB’s Senior Policy Researcher if you have any questions or to be notified when registration for these webinars becomes available.
- Centers for Disease Control - National Center for Health Statistics. (2014). "National health statistics reports." Retrieved from http://www.cdc.gov/nchs/products/nhsr.htm.
- Crews, J. E., Lollar, D. J., Kemper, A. R., Lee, L. M., Owsley, C., Zhang, X., … Saaddine, J. B. (2012).The variability of vision loss assessment in federally sponsored surveys: Seeking conceptual clarity and comparability. American Journal of Ophthalmology, 154(6), S31–S44. doi:10.1016/j.ajo.2011.10.029
- National Center for Health Statistics (2015). National Health Interview Survey, 2013. Public-use data file and documentation. Accessed through Integrated Health Interview Series online data analysis, https://www.ihis.us/ihis/
- Resnikoff, S., Pascolini, D., Etya, D., Kocur, I., Pararajasegaram, R., Pokharel, G. P., & Mariotti, S. P. (2004). Global data on visual impairment in the year 2002. Bulletin of the World Health Organization, 82(11), 844–851. Retrieved from http://www.who.int/bulletin/volumes/82/11/en/844.pdf
- U.S. Census Bureau. (2015). "American Community Survey." Retrieved from
- U.S. Census Bureau. (2015b). Table C18103. 2013 American Community Survey 1-Year Estimates. Retrieved from http://factfinder.census.gov/bkmk/table/1.0/en/ACS/13_1YR/C18103
- Vogt, W. P., & Johnson, R. B. (2011). Dictionary of statistics & methodology: A nontechical guide for the social sciences. (4th ed.). Los Angeles, CA: SAGE Publications.
- West, S. K., & Lee, P. (2012). Vision surveillance in the United States: Has the time come? American Journal of Ophthalmology, 154(6 Suppl), S1–2.e1–2. doi:10.1016/j.ajo.2012.09.004
- Zuckerman, D. M. (2004). Blind adults in America: Their lives and challenges. Washington, DC: National Center for Policy Research for Women and Families. Retrieved from http://www.center4research.org/wp/wp-content/uploads/2010/05/blind02041.pdf