Partial sight and blindness in children of the 1970 birth cohort at 10 years of age.

The prevalence and causes of partial sight and blindness (best corrected distant visual acuity of 6/24 or less) have been studied in a nationally representative sample of 15,000 10-year-old children. The prevalence of blindness (acuity less than 6/60) was between 3.4 and 4.0/10,000. All these children had been registered as blind; less than half were in schools for the blind, the remainder were all in other special schools. The prevalence of partial sight (acuity less than or equal to 6/24 greater than or equal to 6/60) was between 5.4 and 8.7/10,000; less than half of these children were in schools for the visually handicapped or partially sighted; most were in ordinary schools; half were neither registered as partially sighted nor ascertained as in need of special education for visual handicap. The most common cause of partial sight or blindness in this cohort was congenital cataract; the second most common was congenital nystagmus. The study identified a number of children whose best acuity on examination was 6/24 or less who had either no ophthalmological diagnosis or who had been diagnosed as suffering from a refractive error. These children have been included in the study because at the time of the survey they had either not been prescribed spectacles or they had spectacles which they were not wearing; the functional visual level of these children was therefore equivalent to that of those defined as partially sighted.