RESUMO
BACKGROUND: A goal of vision screening is the detection of amblyopia risk factors, including strabismus. The random dot Stereo Butterfly test requires no instruction, has a simple pass/fail response with no monocular clues, and is easily administered. The purpose of this study was to determine whether this test could be used as a cost-effective and reliable component of preschool vision screening. METHODS: The Stereo Butterfly was presented to children with no previous history of ocular problems or treatment. The test was presented with the use of polarized glasses at a 16-inch testing distance. A "pass" was recorded if the patient reported seeing a butterfly; a "refer" was denoted otherwise. Vision and motility measurements were recorded, and the patient underwent a complete eye examination with cycloplegic refraction. RESULTS: A total of 281 children 3 to 6 years of age were tested: 221 children passed the test. Of those who passed, 7 (3.2%) had intermittent strabismus, 1 had a small-angle constant strabismus, 60 failed screening for constant strabismus (of whom 24 [40%] had constant strabismus), and 6 were false-negative results. The sensitivity of the Stereo Butterfly for detecting constant strabismus was 96%; the specificity, 86%. CONCLUSIONS: The Stereo Butterfly test may be a valuable adjunctive tool in vision screening programs for the detection of manifest strabismus because it is easy to administer and effectively detects constant strabismus. It has a high specificity for detection of constant strabismus but, if used alone, the low positive predictive value would allow for many false-positive results.
