A reconsideration of amblyopia screening and stereopsis

Traditional screening measures for amblyopia, including visual acuity, the cover test (to detect the frequently associated strabismus), and the 4 diopter prism test have shortcomings when used with 3 to 4 yr old children who are the most important candidates for visual screening. In the present study, a widely used set of stereotests (Titmus Stereo Fly, Circle, and Animal Tests) were administered to 70 patients with known visual dysfunctions to determine if stereopsis testing, in the form of these tests, constituted a feasible alternative as a screening measure. The results indicated that, with the exception of the relatively fine thresholds of the No. 5 (100 arc sec) to No. 9 (40 arc sec) Circle tests these stereotests are not only unreliable in discriminating patients with amblyopia from normals, but may indicate an artifactual stereoscopic capability. Since a previous screening study reported that children in the 3 to 4 yr old range were unable to pass the No. 5 and above Circles targets, it appears that while stereopsis itself may be a pertinent amblyopia screening measure, this particular set of tests is not.