The first area of investigation is of the development f adaptive processes for accommodation and vergence and their influence on cross-coupling interactions between accommodation and vergence in pre-school children. The main question is whether the postnatal onset of accommodative esotropia is associated with a delay in the development of accommodative adaptation behind the development of vergence adaptation. The second area of investigation is of differential adaptation of the two eyes to uniform disparity (prism) and gradient disparity (afocal magnification) such as that encountered in aniseikonia, muscle paresis and growth factors of the eyes. Studies will determine if separate processes underlie adaptation to uniform and gradient disparity. They will also examine the relation between vergence adaptation to gradient disparity and the apparent changes in Hearing's law for yoked versional eye movements. Experiments will determine if there is a common adaptive process that interacts with all versional eye movements to produce an apparent modification of Hearing's law or if the yoking of each versional system undergoes independent differential adaptation to gradient disparity. The third area of investigation will quantify baseline variability of the phoria and the versional yoking ratio, ocular dominance effects on differential adaptation, as well as temporal and spatial characteristics of differential adaptation to gradient disparity. Experiments will also distinguish between orbit and retinotopic maps for spatially localized vergence aftereffects as well as depth or distance specific vergence aftereffects. Experiments will test for an association between horizontal saccadic vergence with vertical magnification of one ocular image such as that encountered in aniseikonia and asymmetric vergence, and they will also compare the effectiveness of differential image size and differential retinal image feedback as stimuli for differential binocular adaptation. The final section quantifies sensory components and the associated spatial distortions that accompany differential binocular adaptation to non- uniform disparity. The results will identify motor and sensory processes which underlie the spread of concomitance in ocular paresis and the maintenance of yoked versional eye movements during postnatal development.
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