in age- and gender-stratified groups. Chi-square tests were used for analysis of differences in prevalence between genders. Logistic regression was used for analysis of differ- ences in prevalence among age groups. Results During the period from July 2008 to December 2009, a to- tal of 14,606 participants from 5,986 households were re- cruited and underwent an eye examination. Ages of the study participants ranged from 3 to 95 years of age: 6,580 were men and 8,026 were women. Table 1 shows the age and gen- der distributions of the study population. Visual impairment and blindness The overall prevalence of visual impairment was 0.4 ± 0.1% (0.3 ± 0.1% in males, 0.5 ± 0.1% in females) (Table 2), while that in participants over 40 years of age was 0.9 ± 0.1% (0.6 ± 0.1% in males, 1.1 ± 0.2% in females) and was higher in females than males (p = 0.04). The prevalence of visual impairment in participants over 70 years of age was 3.8 ± 0.7% (2.9 ± 0.8% in males, 4.4 ± 0.9% in females) and showed a significant increase with age (p < 0.01). The preva- lence of blindness in either eye of participants over 65 years of age was 0.2 ± 0.1% (0.3 ± 0.2% in males, 0.1 ± 0.1% in fe- Table 1. Number of participants according to age and gender Total 377 3,066 1,561 2,159 2,219 1,866 1,807 1,551 14,606 No 6,171 1,571 679 88 936 790 746 562 Age group (yr) 3-4 5-18 19-29 30-39 40-49 50-59 60-69 ≥70 Total Male 203 1,608 692 905 954 804 784 630 6,580 Female 174 1,458 869 1,254 1,265 1,062 1,023 921 8,026 Age group (yr) Total 5-18 19-29 30-39 40-49 50-59 60-69 ≥70 No 13,702 2,993 1,530 2,117 2,178 1,824 1,717 1,343 Total Prev (%) 0.4 0.0 0.0 0.2 0.1 0.3 1.2 3.8 SE (0.1) (-) (-) (0.1) (0.1) (0.2) (0.3) (0.7) Table 2. Prevalence of visual impairment according to age and gender Visual impairment was defined as a best-corrected distance visual acuity of 0.32 or worse in the best eye. No = number of participants; Prev = prevalence; SE = standard error. KC Yoon, et al. Prevalence of Eye Disease in South Korea males), and there were no statistically significant differences in relation to gender (p > 0.05). Refractive errors The overall prevalence of myopia was 53.7 ± 0.6% (54.3 ± 0.8% in males, 53.1 ± 0.7% in females) (Table 3). The preva- lence of myopia in the group of participants ranging in age from 12 to 18 was 78.8 ± 1.3% (77.9 ± 1.7% in males, 79.9 ± 1.7% in females) and was highest among the age groups (p < 0.01). The prevalence of myopia was higher in females than in males in the 19 to 29 and over 70 years age groups (p < 0.05 for both). The overall prevalence of hyperopia was 10.7 ± 0.4% (9.4 ± 0.4% in males, 12.0 ± 0.5% in females) (Table 3). In the group of participants ranging in age from 5 to 11, the preva- lence of hyperopia was 5.3 ± 0.6% and then decreased with age. From the group of participants ranging in age from 40 to 49, the prevalence of hyperopia again increased with age. The prevalence of hyperopia in the group of participants ranging in age from 60 to 69 and in the age group over 70 years was 43.8 ± 1.4% and 47.1 ± 1.5%, respectively. In all age groups, there was no statistically significant difference in relation to gender (p > 0.05). The overall prevalence of astigmatism was 58.0 ± 0.6% (57.6 ± 0.8% in males, 58.4 ± 0.7% in females) (Table 3), while that in the 70 years or older age group was 92.0 ± 0.8% (92.9 ± 1.2% in males, 91.5 ± 1.1% in females), illustrating a significant increase with age (p < 0.01). In the group of par- ticipants ranging in age from 30 to 39, the prevalence of as- tigmatism was higher in males than in females (p < 0.01). Strabismus The overall prevalence of strabismus was 1.5 ± 0.1% (1.5 ± 0.2% in males, 1.5 ± 0.2% in females) (Table 4). The preva- lence of strabismus in participants over 40 years of age was 1.4 ± 0.2% (1.5 ± 0.2% in males, 1.2 ± 0.2% in females). In the group of participants ranging in age from 3 to 5 years, the prevalence of strabismus was 1.8 ± 0.7% (0.5 ± 0.4% in Male Prev (%) 0.3 0.0 0.0 0.3 0.2 0.3 0.9 2.9 SE (0.1) (-) (-) (0.2) (0.1) (0.2) (0.3) (0.8) No 7,531 1,422 851 1,230 1,242 1,034 971 781 Female Prev (%) 0.5 0.0 0.0 0.1 0.0 0.4 1.5 4.4 SE (0.1) (-) (0.1) (0.1) (-) (0.2) (0.4) (0.9) p-value 0.08 0.82 0.18 0.17 425