Normal and abnormal space perception

The mononuclear spatial judgments made by normal adults are quite accurate and precise. Although relatively little is known about how the spatial sense develops, it is likely that it can be compromised by abnormal visual experience as provided, for example, by strabismus. Previously, we reported that the spatial sense of strabismic amblyopic eyes is distorted, having quantified these distortions as marked inaccuracies in equating spatial extents in the nasal and temporal field and specifying when one target is vertically aligned with another. Distortions--localized "expansions" and "compressions" of spatial values and "bending" of direction lines--characterize the amblyopic eyes of strabismics but not non-squinting anisometropes. Thus, according to our previously published hypothesis, spatial distortions can account for the reduced acuity and abnormal oculomotor behavior of strabismic (but not anisometropic) amblyopic eyes. In the present paper, we provide quantification of another spatial measures--spatial precision--and show that extensive imprecision characterizes the space sense of the strabismic amblyopic eye. We now add spatial imprecision to our original hypothesis as a significant element in accounting for the abnormal sensory and motor behaviors of strabismic amblyopic eyes.