Neuroanatomic abnormalities of primary visual cortex in macaque monkeys with infantile esotropia: preliminary results

To explore the structural basis for visuomotor deficits in infantile esotropia, we examined binocular connections and metabolic activity in the primary visual cortex of two strabismic macaque monkeys. The animals were documented to have onset of natural esotropia in early infancy. Behavioral testing showed that the animals had normal visual acuity in both eyes and the ocular motor deficits that characterize strabismus with onset in infancy. The neuronal tracer substance biotinylated-dextran-amine was injected into ocular dominance columns (ODC) in area V-1 (striate cortex), revealing a paucity of binocular connections between right-eye and left-eye ODCs. The metabolic label cytochrome-oxidase was used to stain neighboring right-eye and left-eye ODCs, revealing inequalities in metabolic activity compatible with interocular suppression. These results show that infantile esotropes have abnormalities of visual cortex structure that correlate with abnormalities in binocular behaviors.