Independent variables included age (ages 18-44, 45-64, and ≥65 years), sex, race or ethnicity (white [white non-Hispanic], African American [black non-Hispanic], Hispanic, and others [others non-Hispanic]), marital status, education (<high school, high school, and >high school), income (poverty income ratio <1, 1≤poverty income ratio<2, and poverty income ratio ≥2), health insurance, diabetes, vision or eye problems, and region (Northeast, Midwest, South, and West). Insurance groupings were collapsed from more detailed categorizations used in the NHIS. Respondents who had only public insurance (such as Medicare, Medicaid, Indian Health Service, military insurance, or other public or government insurance) were grouped into the public category, and the private group was for those with private coverage only. Respondents with both public and private coverage were categorized as both, and those who reported no coverage were categorized as none. Additionally, as the insurance status of persons aged 65 years and older may be unique because of Medicare, we further stratified this cohort (those aged ≥65 years) by 3 categories with a method previously used by the National Center for Health Statistics and assessed the influence of Medicare on eye care use.39 These categories were Medicare only, Medicare plus other public coverage, and private (with or without Medicare). For those between the ages of 18 and 64 years, the 3 insurance categories used were public only, private (with or without public), and uninsured.