Prevalence Estimates – Vision Loss and Blindness

Methods

The Vision and Eye Health Surveillance System prevalence estimates of vision loss and blindness were estimated using a statistical modeling approach called Bayesian meta-regression, which researchers used to combine information from multiple VEHSS data sources into a single summary estimate. The VEHSS estimates use measured visual acuity data from the National Health and Nutrition Examination Survey (NHANES) as the reference point dataset to create output based on the characteristics and performance of the NHANES vision exam. In addition to NHANES, the estimation model used population-based study data to provide additional evidence, and self-reported survey data to provide information on variation by state, county and among under-represented population groups.

Full details of the methods are available in the publication and online appendix Flaxman et al 2021.

More Visual Function Indicators in the VEHSS Data Explorer

CDC uses the VEHSS composite estimate as the primary estimate to assess the percentage of people with uncorrectable vision impairment and blindness in the United States by state, county, and across different age groups, race/ethnicity categories, and sex. However, VEHSS also contains several other data sources with prevalence or useful information about vision loss and blindness. Readers should consider all sources when deciding which to use to fit their specific information needs.

Self-Report Measures: VEHSS contains estimates of individuals who reported difficulties with their vision during their survey responses to the American Community Survey (ACS), Behavioral Risk Factor Surveillance System (BRFSS), National Health Interview Survey (NHIS), and the National Survey of Children’s Health (NSCH). These estimates represent people with both correctable and uncorrectable vision problems. Estimates from these sources are sensitive to question wording and the data collection mode (Rein et al. Vision Impairment and Blindness Prevalence in the United States: Variability of Vision Health Responses across Multiple National Surveys).  More information comparing different sources of self-report measures is published. The VEHSS vision loss prevalence estimates use two sources of survey self-reported information (ACS and NSCH) to estimate variations in vision loss and blindness geographically (ACS) and among children (NSCH).

Measured Acuity: VEHSS contains national prevalence estimates of measured, correctable and uncorrectable visual acuity deficits from NHANES. The VEHSS vision loss prevalence estimate uses this information and population-based study data to estimate the total number of people with vision loss and blindness in 2017. The original NHANES estimates are available on the VEHSS Data Explorer but are only available at the national level and were last collected in 2008.

The VEHSS Data Explorer also contains information on patients with measured vision impairment or blindness as measured by ophthalmologists and reported to the Intelligent Research in Sight (IRIS) Registry©. The IRIS Registry© data can be used to look at state and population differences but are only applicable to people who visited an ophthalmologist and participated in the IRIS Registry©. Finally, the VEHSS Data Explorer contains a review of selected published vision examination studies. Published results from some of these studies were used to create the VEHSS vision loss prevalence estimate.

Utilization Measures: The VEHSS Data Explorer contains information on using health services related to vision problems as coded in insurance claims information obtained from Medicare, Medicaid, commercial medical insurance (MarketScan), and managed vision care (Vision Service Plan [VSP]) programs, as well as services included in ophthalmology electronic health records summarized by the IRIS Registry©. These estimates measure the proportion of patients who received at least one medical service coded with a diagnosis code for vision impairment or blindness. These measures can be used to assess the proportion of people who received services for diagnosed vision problems.

Summary

Using the VEHSS composite estimates of vision loss is CDC’s best way to estimate the percentage of US residents that have vision loss and blindness and to understand the distribution of vision loss and blindness by demographic and geographic factors. These estimates are based on uncorrectable visual acuity loss, and therefore represent permanent vision loss that cannot be corrected with glasses. These differ from survey self-report estimates, which represent self-assessed visual function, presenting acuity loss included in NHANES, and measures visual acuity based on a person’s current use of glasses or contacts.

Users should consider these differences in measures when deciding if the composite estimates of vision loss, survey self-report, or other data sources are most appropriate to address their research objectives.