Validity of TNO cards as a screening test for defects of binocularity in children

Background: Vision screening in children usually comprises of visual acuity assessment for distance alone. Binocularity is not routinely checked. This study evaluates the validity of the TNO cards stereopsis test as a screening tool for defects of binocularity in children. Methods: In this cross-sectional observational study, 200 children, aged 5–15 years, visiting the outpatient department of a tertiary eye care institute, had their near stereoacuity assessed using the TNO cards test. The number of children with amblyopia, strabismus and refractive error were compared among those who passed (120 arc sec or better) or failed (worse than 120 arc sec) the screening test. The sensitivity and specificity of TNO cards as a diagnostic test for the above conditions were calculated. Results: The sensitivity of TNO cards to diagnose amblyopia, strabismus and refractive errors was 100%, 80% and 22.1%, respectively. The specificity for the same was 96.8%, 93.3% and 100%, respectively. The area under the curve by plotting receiver-operating characteristics (ROC) for diagnosis of these conditions was 0.996, 0.871 and 0.610, respectively. Conclusion: The TNO cards test is effective in screening children for amblyopia and strabismus. However, this test needs to be combined with vision assessment for effective screening of refractive errors.