208 AM J OPTOM & PHYSIOL OPTiCS Vol. 57, No. 4

Trials, or stimulus presentations, are plotted against fusional convergence demand. From this figure, it is apparent that when convergence demand is low, performance is better. When convergence demand approximates the recovery point, response errors occur (decreasing slightly subsequent convergence demand). With continued practice, improved performance reflects an increased ability to fuse the greater convergence demand stimuli. This is represented by an increase in the slope of the convergence line.

Figs. 2-5 depict the final RDS fusional convergence demand obtained by each patient at the end of each training session. The dashed vertical line separates the experimental procedure, operant RDS convergence training, from the vectogram performance levels attained during previous vision training. It is readily seen that all four patients showed dramatic improvements in RDS convergence ability during experimental training. Since vectogram convergence ranges also improved during RDS training, it can be assumed that the effects of RDS training transferred to vectogram testing. This improvement occurred in terms of both vectogram convergence break and recovery points.

Another indication of the effectiveness of RDS convergence training is represented by a general change in each patient’s visual performance during subsequent regular vision training sessions. For patient JH, vectogram break and recovery points did not always correspond well with verbal report of size and distance localization.e Following RDS training, correspondence occurred regularly. In addition, prior to RDS training, cover testing indicated a 15 pd intermittent exotropia at distance occurring approximately 50% of the time. After RDS training, an 8 A exophoria was measured via cover testing.

Patient PL, an intermittent exotrope who deviated both at distance and at near, showed changes similar to patient JH. Before RDS training, vectogram training yielded inconsistent findings in which reports of suppression on a good number of vectogram training trials predominated. After RDS training, fewer reports of suppression occurred along with obtained convergence ranges greater than 30 A.

The vectogram break and recovery point data shown in Fig. 2 represent findings only on those trials in which correspondence occurred with verbal reports of size changes and distance localization.

FIG. 1. Represents increases and decreases in convergence demand for patient P1 during 105 trials during session 6 of operant RDS convergence training. Increases in the slope of the convergence line are a function of correct responses to disparity RDS of increased convergence demand. Plateaus or decreases in the slope of the convergence line represent correct responses to ROS without disparity or incorrect responses to either training stimulus. resoectivelv.