Accommodative stimulus/response function in human amblyopia.

Three parameters are essential to describe static accommodative behavior in a comprehensive, quantitative manner: the slope of the stimulus/response curve, the depth of focus, and the tonic response. These parameters were obtained in amblyopes, former amblyopes, strabismus without amblyopia, and normals. Results showed that the accommodative response in the amblyopic eye was characterized by a reduction in the slope of the stimulus/response curve and increased depth of focus. Similar abnormalities but of lesser magnitude were found in the non-dominant eye of some former amblyopes and some strabismus without amblyopia. Orthoptic therapy always increased the slope of the stimulus/response curve in the amblyopic eye. We believe that the reduced accommodative responses found in amblyopic eyes reflect a primary sensory loss over the central retinal region that occurs as a result of prolonged, early, abnormal visual experience associated with the presence of strabismus and/or anisometropia.