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sions, both RDS and vectogram convergence ranges improved dramatically. However, during sessions in which RDS were presented without any convergence demand, the control subjects demonstrated little or no improvement in convergence ability as measured during vectogram testing. The second baseline assessment also supports the finding that the RDS and vectogram convergence ranges of the control subjects were about the same as during the initial baseline and significantly lower than that of the experimental subjects. However, when the control subjects received subsequent RDS convergence training, changes in RDS and/or vectogram convergence performances occurred.

DISCUSSION

All four young patients in the first experiment demonstrated similar results. Prior to RDS convergence training, little or no improvement in convergence ranges occurred with vectogram training during regular vision training sessions. Subsequent RDS convergence training resulted in a gradual increase in convergence ranges during each training session. Moreover, there was a concomitant transfer of convergence ability evidenced during vectogram testing. These findings occurred for all children within 5 to 10 RDS convergence training sessions.

The success of operant RDS convergence training was most likely related to the combined effects of a number of factors provided during training. For example, the use of RDS as training stimuli did not allow the use of monocular contour cues to aid responding as in vectogram training. Discrimination training presumably facilitated patients’ attention to relevant cues differentiating stereograms with disparity from those not containing disparity, a feature not present in traditional vectogram training. Patient motivation and attention were directly manipulated and encouraged by the use of response-contingent positive reinforcement and immediate response feedback. The automated procedure used to present stimuli and record responses did not allow clinician bias in interpreting patient responses or unintentional prompting

of patient answers. Furthermore, the whole procedure placed less emphasis on verbal communication skills of our young uncooperative patients. Finally, the precise and automatic manner in which preprogrammed changes in convergence demand took place was most likely a primary factor in generating large increases in convergence ranges. It is unlikely that such gradual and small incremental and decremental changes in convergence demand could have been accomplished during the course of standard vectogram training. Further controlled studies are planned in order to evaluate the relative contribution of each of the factors contained in the present procedure.

The second experiment demonstrated that improvement in convergence ranges was due to programmed increases in convergence demand rather than exposure to stereograms containing no convergence demand. Experimental subjects receiving RDS convergence training demonstrated increased convergence ranges, whereas control subjects did not. This finding, although not unexpected, supports the notion that strict attention should be paid to the manner in which changes in convergence demand are programmed in convergence training.

The findings from experiment 1 not only demonstrated a relatively direct transfer of convergence skills acquired during RDS training to standard vectograms, but also indicated that such training can affect more general binocular dysfunctions. For example, one of our young patients, originally exhibiting an intermittent exotropia prior to training, was found to have an exophoria following training. Thus, the operant RDS convergence training procedure might be helpful in reducing the amount of deviation in intermittent strabismics.

In summary, although the present operant RDS convergence training technique was performed with fairly sophisticated equipment, we feel that the general characteristics of the procedure might easily be translated into an effective and efficient clinical tool. The training of convergence skills, especially with young, poorly motivated, inattentive, and communicatively inexperienced patients, should always involve a procedure demanded by these patient