2007 年 25 巻 2 号 p. 262-266
Visual acuity tests are implemented to detect functional amblyopia (lazy eye) and other diseases in the national health examination for children of three years of age. Children who can accurately identify symbols corresponding to a visual acuity rate of 0.5 with both their left and right eyes are judged to have passed the test. This standard was adopted with due consideration for the average visual acuity of children aged three years and zero months and adopted as a benchmark in order to check for the presence of abnormalities requiring treatment such as functional amblyopia among this age group. It was found that children who passed the visual acuity test had no signs of ophthalmologic disease requiring early therapeutic intervention. In contrast, children who failed to pass the visual acuity test occasionally suffered ophthalmologic disease requiring immediate treatment. Accordingly, the standard adopted was regarded as reasonable. The test utilizes Landolt ring charts or picture optotypes, the former of which are characterized by remarkable precision. The latter, meanwhile, are characterized by excellent availability as a rating tool. This screening method has contributed to promotion of early detection and treatment of functional amblyopia. As a result, the majority of children diagnosed with amblyopia are able to acquire the normal visual acuity before entering elementary school.