Purpose:
To compare the estimated prevalence of myopia in the 1971-1972 U.S. population with myopia prevalence estimates from the 1999-2004 U.S. population.
Methods:
The 1971-1972 (71-72) National Health and Nutrition Examination Survey (NHANES) provided the first nationally representative estimates for prevalence of myopia in the U.S. In the 71-72 NHANES, myopia was defined based on lensometry (for those with presenting visual acuity (VA) ≥20/40) and on noncycloplegic retinoscopy (for those with presenting VA ≤20/50). We applied the 71-72 NHANES definition of myopia to vision examination data from the 1999-2004 (99-04) NHANES to compare prevalence estimates of myopia in the U.S. for the two surveys (conducted 30 years apart), for persons aged 12-54 years. For eyes with presenting VA ≥20/40, spherical equivalent (SphEq) was calculated from lensometry measurements of the current distance correction; if SphEq <0, they were classified as myopic, otherwise they were classified as non-myopic. Persons with good presenting VA (≥20/20 for NHANES 71-72; ≥20/25 for NHANES 99-04) who did not wear corrective lenses for distance were classified as non-myopic. Persons with presenting VA ≤20/50 were classified as myopic or non-myopic based on retinoscopy (71-72) or autorefractor (99-04) measurements of refraction. Prevalence estimates were based on data from right eyes of participants and were computed using appropriate weights to account for the NHANES' multistage probability sampling design.
Results:
In NHANES 71-72 and 99-04, 4,436 and 18,732 persons, respectively, had sufficient data to classify their myopia status. The estimated prevalence of myopia was statistically significantly higher in 99-04 than in 71-72 for all age groups for both non-Hispanic black and non-Hispanic white participants (see Table).
Conclusions:
The estimated prevalence of myopia in the U.S. appears to be higher in 1999-2004 than in 1971-72. Changes in the composition of the non-Hispanic white and non-Hispanic black population in the U.S. may account for some of this difference. Another possible explanation is a change in the environmental risk factors for myopia for later birth cohorts.
Keywords: clinical (human) or epidemiologic studies: prevalence/incidence • myopia