Abstract
A longitudinal study of stereoacuity levels of 859 children at 7 years, 811 children at 9 years and 796 children at 11 years was conducted using the TNO random dot stereotest. The prevalence of defective stereoscopic vision was found to be between 2.1 and 3.2 per cent. A further 10-16 per cent of children had only moderate stereoacuity levels when compared with their peers. The stereoacuity levels achieved by most of the children improved with age, but the rank order correlations for the stereoacuity levels between ages 7 and 9, and ages 9 and 11, were small. Defective stereopsis and poor stereoacuity levels were clearly associated with manifest strabismus and problems of visual acuity, and if failure to pass the quantitative plates was a cut-off point for screening purposes most of the children with visual problems would have been identified.