Functional Magnetic Resonance Imaging of Binocular Interactions in Visual Cortex in Strabismus

PURPOSE: To observe changes in primary visual cortical activation associated with perceptual suppression in individuals with strabismus, using functional magnetic resonance imaging (fMRI). METHODS: In Phase 1, pilot data were collected from 1 control and 8 strabismic participants, including 5 with amblyopia. In Phase 2, results were collected from 7 participants with strabismus (2 recalled and 5 new), including 2 with amblyopia. fMRI compared primary visual cortex activation in two conditions: visual stimuli presented to both eyes, to evoke perceptual suppression of one eye in individuals with strabismus, and visual stimulation presented only to one eye. RESULTS: Visual cortical activity modulations positively correlated with perceptual suppression were seen in 3 of 5 non-amblyopic Phase 2 study participants, but not in amblyopic subjects. CONCLUSION: Cortical activity modulations correlated with modulation of strabismic suppression are detectable in non-amblyopic individuals using fMRI, suggesting a neural basis for strabismic suppression in primary visual cortex.