Monocular spatial distortion in strabismic amblyopia.

We examined monocular spatial vision of strabismic amblyopes by measuring errors of relative directionalization (specifying whether or not two targets are in vertical alignment) and partitioning (equating left- and right-field spaces). Abnormally large errors were made when fixation occurred with the amblyopic eye; these errors did not attributable to reduced acuity, unsteady fixation, or eccentric fixation. From the results we infer that monocular space perception of strabismic amblyopic eyes is severely distorted and is characterized by "bending" of vertical lines of direction and by local "compressions" and "expansions" of horizontal spatial values. Such distortions can readily account for many of the oculomotor abnormalities of the amblyopic eye as well as for the strabismic subject's phenomenological description of the difficulties experienced in using this eye--difficulties that are typically much worse than the reduced acuity would predict.