The effects of short-term experimental strabismus on the visual system in Macaca mulatta.

Experimental esotropia was produced surgically in infant rhesus monkeys (Macaca mulatta) for brief periods of time. Electrophysiological studies of the visual cortex showed that esotropia of only 2 weeks duration in an infant monkey is sufficient to cause a marked shift of dominance in favor of the fixating eye and to virtually extinguish cortical neuronal responses from the esotropic eye. In the lateral geniculate nucleus cell (LGN), shrinkage of 6% to 8% occurred in the parvocellular layers connected with the esotropic eye, the magnocellular layers showing no changes. After the fixating eye had been sutured for 3 weeks, a complete reversal of the cortical physiology in favor of the esotropic eye occurred, whereas no recovery in cell size was observed in the LGN. Surgical realignment of an esotropic eye caused recovery of cortical neuronal responses from the formerly esotropic eye, but the number of binocularly responsive cells remained reduced.