Stereo Butterfly test appears reliable as adjunct to preschool vision screening

J Pediatr Ophthalmol Strabismus. 2009;13(4):354-356.

The Stereo Butterfly test offered detection of strabismus in a group of children, a study showed. However, the test should be used in conjunction with other preschool screening protocols.

"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," the authors said. "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."

The authors set out to determine the cost-effectiveness and reliability of the Stereo Butterfly test as a component of preschool vision screening.

The study included 281 children ages 3 to 6 years with no history of ocular problems who took the Stereo Butterfly test. They wore polarized glasses at a 16-inch viewing distance. A child who saw a butterfly was scored as a pass; a child's failure to see a butterfly was scored as a refer.

The children also underwent a full eye examination with cycloplegic refraction, vision measurement and motility measurement.

Of the 221 children who passed the test, seven children (3.2%) were identified with intermittent strabismus. One child had small-angle constant strabismus.

Sixty children failed screening for constant strabismus; 24 of those children (40%) had constant strabismus. Six had false-negative results.

The Stereo Butterfly test had a sensitivity of 96% and specificity of 86%, the authors said.