Projecting the Prevalence of Vision Loss and Eye Disorders

The Vision Problems database reports the prevalence of vision loss and eye disorders in the United States. We include the following disorders from the Vision Problems database:

  • Visual impairment,
  • Blindness,
  • Glaucoma,
  • Cataract,
  • Age-related macular degeneration, and
  • Diabetic retinopathy

For each condition, the Vision Problems database reports the prevalence rate by sex, race and age category. The Vision Problems analysis also reports the prevalent population with each condition by race, sex, and age category based on the 2010 US Census population estimate.

The race categories include non-Hispanic whites, non-Hispanic blacks, Hispanics (which is treated as race), and all others. The Vision Problems in the US database reports prevalence for ages 40-49, and by 5-year age groups through age 79, and for ages 80+. AMD prevalence is not reported for persons younger than 50. Diabetic retinopathy is reported in 40-49, 50-64, 65-74, and 75+ age groups. VPUS does not include any prevalence estimates for the population younger than age 40 due to data limitations.

We calculated annual projections of the prevalent population by multiplying age, race, and sex-specific prevalence rates for each disorder by annual US Census population projections for each corresponding demographic group from years 2014 through 2050. Our predictions exactly match the Vision Problems estimates in 2010, but our baseline results are higher than the Vision Problems results due to the difference between the 2010 Census estimates and the 2014 Census projections.

We estimated per-capita prevalence by single year of age in order to fit prevalence data to future population projections. For each sex, race, and disorder combination, we created a prevalence curve-a line depicting the single-year prevalence for ages 40 to 100, or 50-100 in the case of AMD. We converted the step-based age bin prevalence rates to annual prevalence rates through the following process:

  1. We adjusted the Vision Problems in the US prevalence estimates, based on the 2010 US Census population estimate, to fit the 2014 US Census population projection.
  2. We calculated the mean population age for each age group for which prevalence was reported.
  3. We used regression to fit a line between each consecutive age group, based on the prevalence of each age group at the mean age of each age group.
  4. We adjusted the slope of the line between each subsequent age group to ensure continuity of the prevalence estimate line.
  5. We adjusted the height of the line to ensure predicted prevalence of each age group exactly matched the 2014 prevalence estimate calculated in step 1.

Figure 6.1 shows the Vision Problems values and the predicted values for the prevalence of visual impairment among Hispanic males. Using this annual prevalence prediction process “evens-out” the prevalence estimates by age, but also serves to approximate high prevalence rates among the oldest Americans, including those aged 90+. This is an important consideration because while the prevalence estimates in the baseline year are identical whether using either approach, in future years the predicted annual values result in slightly higher projected prevalence. This is because the US population is projected to not only grow, but to shift to older ages. While this age shift causes increased prevalence projections, the impact is more pronounced using the annual predictions because of the high projected growth of the population aged 90 and older, at which point the predicted annual prevalence rates become much higher than the pooled 80+ estimates from Vision Problems database.
 

Figure 6.1. Predicted Annualized Prevalence versus Age-bin Prevalence of Visual Impairment

Figure 6.1. Predicted Annualized Prevalence versus Age-bin Prevalence of Visual Impairment
Figure 6.1. Predicted Annualized Prevalence versus Age-bin Prevalence of Visual Impairment

Very limited data exists on the prevalence of eye disorders and vision loss at these ages; most studies including Vision Problems in the US, the original EDPRG studies, and national surveys such as the National Health and Nutrition Examination Survey (NHANES) top-code age at 80 or 85. Many studies, including NHANES, also either under-report or exclude institutionalized individuals, so these studies may not capture prevalent cases among individuals in long-term care, likely excluding a substantial proportion of the population of vision disorders. Nearly all disorders in Vision Problems in the US saw substantial increases in prevalence among the 80+ population compared to younger age groups, and our single-year prevalence predictions continue this trend to age 100. In many cases, this yields very high prevalence predictions at ages approaching 100.

While nationally representative prevalence data at these ages is not available in the US, a UK-based study of vision loss among the elderly by Evans et al supports this trend, and in fact shows even higher increase in prevalence from ages 80-84 to 90+ than we predict.[15] For example, Evans et al finds the prevalence of visual impairment and blindness more than triples from ages 80-84 to ages 90+, while in the same ages our predicted annual prevalence rates increase by about 150% and 180%, respectively. This supports our assumption that prevalence continues to increase after age 80.