suppression scotoma

The region of one eye's visual field that the brain switches off during binocular viewing to prevent double vision and confusion. It disappears as soon as the other eye is covered, because there is nothing left to suppress^1,4. In strabismus a central scotoma removes the confusing foveal image and a peripheral scotoma at the projection of the fixation point removes the double image, and the shape follows the deviation: nasal retina in esotropia, a larger temporal area in exotropia^1,2,3.

Suppression differs from amblyopia, which is a loss of acuity that persists with the other eye covered; constant suppression of one eye can lead to amblyopia, while suppression that alternates between the eyes usually does not². The Worth four dot test shows whether suppression is present and how large the scotoma is, and the 4 prism diopter base-out test finds the small central scotoma of monofixation syndrome and microtropia⁵.