Vision Screening Online Training Program
Module 7 (continued): Stereo Acuity Test - Stereo Butterfly
(C&TC: Usually performed by a nurse or medical assistant)
Testing for stereo acuity is checking the child’s ability to see the depth or distance of an object. In order to have depth perception, both eyes must work together. When both eyes are properly functioning, the brain fuses the two images gained from each eye to form one image. If one eye is not functioning properly, as in the case of strabismus or amblyopia, the child’s brain will be unable or have a difficult time fusing images, affecting their ability to see depth properly. In these cases, the child will not be able to see the image portrayed on the stereo acuity test.
Stereopsis measurement should be performed before the eyes are dissociated by tests such as the cover test.
|Ages:||Age 3 years through 8 years (C&TC) or 3rd grade (Early Childhood and school screenings).|
|Purpose:||To check for problems with stereo acuity or depth perception which tend to be an occurrence for children with strabismus.|
|Description:||By noting if the child is able to see the raised “butterfly” while wearing special glasses, the observer is able to check for stereo acuity problems.|
Stereo butterfly card, and polarized glasses.
|Facilities:||A well-lit, glare free location|
|Pass:||Child is able to point to the butterfly at least 4 times at 20 inches and 40 inches.|
|The child cannot distinguish the butterfly figure in the stereo butterfly card, or can only see it when the card is approximately 20 inches or closer.|
|<-- Previous||Module 7
Page 2 of 2