Spatial localization in esotropia: Does extraretinal eye position information change?

PURPOSE. TO investigate the accuracy of spatial localization in children wi th a specific type of convergent strabismus, fully accommodative esotropia. METHODS. Two groups of children, with right and left fully accommodative es otropia, respectively. pointed at targets located centrally and eccentrical ly on a computer touchscreen without being able to see their hands. The siz e and the direction of the horizontal pointing responses were recorded unde r two conditions: when their eyes were aligned (wearing spectacles) and whe n they were squinting (not wearing spectacles). A group of children without strabismus but with hypermetropia mere assessed as controls. RESULTS. For both fully accommodative groups, the pointing responses to the central target shifted in the direction of the nonsquinting eye when devia tions were manifest. No difference was found for the eccentric targets. No difference was found for the hypermetropia group with any target. CONCLUSIONS. These results are consistent with an alteration in the extrare tinal eye position information (efference copy, extraocular muscle proprioc eption, or both) that is used in spatial localization.