Strabismic suppression depends on the amount of dissimilarity between left- and right-eye images

Suppression in strabismus is more likely to occur when the images for the left- and right-eye are similar. In this study the relationship between the depth of strabismic suppression and the amount of dissimilarity between the images was quantified. Six subjects with microstrabismus looked at two identical colorful, cartoon images via mirrors. In the middle of each screen was a circular aperture with an opal glass, which was illuminated from the back by a halogen lamp during 300 ms with a gradual on- and offset in intensity. In the circular aperture images that slightly differed in shape were presented to both eyes. The dominant eye was presented a circle, the squinting eye a circle that, in four steps, changed its shape into a square. Under each of these four conditions, the image for the dominant eye was attenuated progressively by neutral density filters. When the image for the squinting eye was perceived, the depth of the suppression was thereby measured. It was found that suppression decreased with dissimilarity of the images.