pairment of the superior visual field and central vision in se- vere cases. Even though blepharoptosis is generally known to exist below 4 to 5 mm of MRD1 in Western populations, there are no accurate definitions and available data on the prevalence of blepharoptosis, particularly among Asians. Except for Nigeria, the prevalence of blepharoptosis has not been reported. In the Nigeria study, blepharoptosis was de- fined as the amount of the cornea covered by more than 2 mm by the upper eyelid, and the prevalence of blepharoptosis among school children under the age of 16 years was 1.2% [57]. There are no accurate diagnostic criteria about blephar- optosis for Asian or Korean populations. However, depend- ing on race, there are many differences in facial anatomy. Therefore, we defined blepharoptosis as less than 2 mm of MRD1 with consideration for anatomical differences of the eyelids and orbit. In our study, the prevalence of blephar- optosis in the 3 to 5, 6 to 11 and 12 to 18 age groups were 9.9%, 11.1% and 9.1%, respectively, higher than prevalences reported in Nigeria. One of the main objectives of this study is to estimate the prevalence of blepharoptosis in Koreans. In future studies, appropriate diagnostic criteria should be es- tablished for use in Korean people. The prevalence of cataract has been reported as 22.3% in the United States [29], 40.4% in Myanmar [55] and 35.0% in China [28]. In the present study, the prevalence of cataract in adult Korean over 40 years of age was 40.2%. The preva- lence of cataract was similar to those reported in Myanmar and China, where no statistically significant differences in prevalence were observed in relation to gender. However, in the United States and Korea, females showed a significantly higher prevalence of cataract than males. Several population-based studies have examined the prev- alence of pterygium and have indicated a prevalence ranging from 1.2% in a White population in urban Australia [21] to 33.0% in a Chinese population of subjects 50 years or older in Doumen County, Southern China [58]. In our study, the prevalence of pterygium in subjects over 40 years of age was 8.9%. Differences in prevalence of pterygium were observed among these studies. However, dominance in male gender and old age associated with formation of pterygium were similar to those observed in other studies. Large-scale population-based studies have been conducted over the past two decades in order to identify the prevalence and risk factors of AMD [2,6,12,15-19,26,32,60]. Studies have demonstrated variations in the prevalence and risk fac- tors of AMD. In the Blue Mountains Eye Study, the preva- lence of early AMD was 8.7%, and the prevalence of late AMD was 1.1% [19]. In the Beijing Eye Study, the preva- lence of early AMD and late AMD was 5.1% and 0.3%, re- spectively [32]. In addition, the prevalence of early AMD and late AMD was 3.5% and 0.5% in the Funagata Study [26]. In the present study, the prevalence of early AMD and late AMD was 5.1% and 0.5%, respectively. Our study showed a low prevalence of AMD compared to those in White populations. In addition, the prevalence of AMD in KC Yoon, et al. Prevalence of Eye Disease in South Korea our study was similar to those of Chinese and Japanese populations. The prevalence of diabetic retinopathy in the United States was reported as 28.5% to 40.3% [13,14]. There are many population-based data on the prevalence of diabetic retinop- athy in Asia [61-63]. In Taiwan, 35% of 527 diabetic subjects over 40 years of age had diabetic retinopathy based on clinical examination [61]. However, recent studies in India indicate a much lower prevalence of diabetic retinopathy [62,63]. In the present study, the prevalence of diabetic retinopathy (subjects over 40 years of age) was 13.4%, much lower than the prevalence reported in the United States or Taiwan. This relatively low prevalence of diabetic retinopathy may be due to a short duration of diabetes in our study population. Glaucoma is believed to be the leading global cause of sur- gically irremediable blindness [64]. In the Baltimore Eye Survey, the prevalence of POAG was approximately four times higher in black people (4% to 5%) than in white people (1.1%) [65]. In recent years, several studies have been con- ducted on the epidemiology of glaucoma in Asian people [22-24,27,66]. The prevalence ranges of POAG and PACG have been reported as 1.6% to 3.9% and 0.4% to 1.0%, respectively. In this study, the prevalence of POAG and PACG was 2.0% and 0.1%. The prevalence of POAG was similar to those reported in other Asian countries [22-24,27,66]. In con- trast, the prevalence of PACG was lower than those reported in other Asian countries [22-24,27,66]. Results of this study might have been underestimated as only the Van Herick method was used in the diagnosis of PACG. Accurate epidemiological information may contribute to the proper delivery of health care, preventive screenings, and rehabilitative services to individuals with eye diseases. This study provides standardized protocols for examination of oc- ular diseases and improvement of ocular examination ca- pacity through education and quality control. Databases con- taining results from examination of eye diseases and results of quality control can be utilized in future clinical studies. In addition, methodology used in this survey can be utilized as a guideline for use in new population-based studies which will be performed in the nation. In summary, our nation-wide study demonstrated the prev- alence of major eye diseases and potential ocular dis- ease-vulnerable groups in Korea. To the best of our knowl- edge, this is the first nation-wide epidemiologic study con- ducted by both the Ophthalmologic Society and the CDC and is a powerful tool for use in investigation of the national prevalence of disease conditions. Further studies are needed using on-going surveys in order to better understand the etio- logic or risk factors that may be associated with ophthalmo- logic diseases and to evaluate proper interventions aimed at prevention of disease-related disabilities. Conflict of Interest No potential conflict of interest relevant to this article was 431