Vertical fixation disparity curve and the effects of vergence training in a normal young adult population

The effects of vertical vergence training on the slope of the vergence fixation disparity (VFD) curve in a normal, young adult population were studied. Forty-five subjects with normal vision and binocular function underwent vertical vergence training for a week. Training was done using a vertical prism bar, and the vertical fixation disparity was measured using the Disparometer. In general, vertical prism bar training provided a long-term effect, both increasing the vertical fusional amplitude and flattening the slope of the VFD curve.