County-Level Correlation Observed Between Poverty and Visual Acuity Loss in US

A recent study observed a positive county-level correlation between poverty and visual acuity loss or blindness prevalence, confirming previous findings on the same topic.

Data from the county-level analysis in the United States report that nonmetropolitan counties had a lower density of ophthalmologists (2.19 per 100 000 persons) compared with metropolitan counties (6.29 per 100 000 persons).

“Data identifying geographic variation in the prevalence of visual acuity loss can be used to guide interventions to improve eye care services, as counties with a higher prevalence of visual acuity loss may have less access to and use of eye care services,” wrote study author Elizabeth A. Lundeen, PhD, MPH, Division of Diabetes Translation, Vision Health Initiative, US Centers for Disease Control and Prevention.

In order to better understand the distribution of vision loss in the US and enact effective interventions and policies, there may need to be a collection of data on local geographic variations. At the moment, the current information on severe vision loss prevalence below state level is based on single-source data.

Thus, the current analysis provided estimates for US counties. Lundeen and colleagues used bayesian metaregression to combine multiple data sets to produce county-level prevalence estimates for visual acuity loss or blindness.

They used data from 5 population-based studies to calculate the combined prevalence of visual acuity loss (best-corrected visual acuity, 0.3 logMAR or greater [20/40 or worse Snellen score]) or blindness (1.0 logMAR or greater [20/200 or worse Snellen score]) by age, sex, race, and ethnicity.

Investigators performed identical calculations on data from the National Health and Nutrition examination Survey (1999 to 2008) for persons in whom autorefraction was used to correct presenting VA. Then, the self-reported vision impairment and blindness data from the 2016 National Survey of Children’s Health and 2017 American Community Survey were incorporated to provide data on children ≤12 years old and residents of institutional group quarters.

The investigation revealed significant geographic variation in county-level prevalence of visual acuity loss or blindness. Data show the crude prevalence ranged from 0.75% (95% uncertainty interval [UI], 0.47 - 1.09) in Douglas County, Colorado to 13.16% (95% UI, 7.18 - 18.41) in Kalawao County, Hawaii.

Further, the reported data show the standardized prevalence ranged from 0.99% (95% UI,  0.53 - 1.50) in Cumberland County, Maine to 10.88% (95% UI, 5.18 - 16.72) in Clay County, Kentucky.

The findings suggest county-level standardized visual acuity loss or blindness prevalence was positively correlated with the percentage of the county’s population living below the poverty level (r, 0.40).

From a county-level analysis on availability of eye professionals, 71.1% of counties in the South were in 1 of the lower 2 quartiles of ophthalmologist and optometrist availability. Investigators noted the South had the lowest number of providers per capita.

Data show the proportion of counties with no ophthalmologists is higher in nonmetropolitan counties (67.0%) in comparison to metropolitan counties (35.3%).

“In addition to the previously discussed limitations of this analytic approach, our results are limited by the lack of county-level measurement of the relative prevalence of visual acuity loss vs blindness,” Lundeen concluded.

The study, “County-Level Variation in the Prevalence of Visual Acuity Loss or Blindness in the US,” was published in JAMA Ophthalmology.