The KNHANES is an ongoing population-based, cross-sectional epidemiological survey conducted in South Korea. Annually, 4,000 households in 200 enumeration districts were selected by a panel to represent the civilian, non-institutionalized South Korean population using the stratified, multistage clustered sampling method based on the 2005 National Census Data. In KNHANES, sample design and size are estimated so that annual survey results represent the whole population in Korea. Therefore, annual survey results can be used as statistics to represent the overall Korean population. All members of each selected household were asked to participate in the survey, and the rate of participation in the past several cycles ranged from 79% to 84%. From July 2008, ophthalmologic interviews and examinations have been conducted. All examination and health interviews were conducted by trained teams in mobile centers, while nutrition surveys were performed in individual households.
This survey is aimed to determine the prevalence of the following vision status and common eye diseases in a population-based sample of Koreans: visual impairment and blindness, refractive errors, strabismus, blepharoptosis, cataract, pterygium, diabetic retinopathy, age-related macular degeneration (AMD), and glaucoma. The ophthalmologic survey was designed to be conducted over 5 years from 2008 to 2013. The present study includes interim data from a survey conducted from July 2008 to December 2009.