210 AM J OPTOM & PHYSIOL OPTICS Vol. 57, No. 4

A third intermittent exotropic patient, PM, could only demonstrate 5pd fusions] convergence ranges prior to RDS training. Though his progress during RDS training was relatively slow, improvement in both RDS and vectogram convergence ability was achieved. Patient PM, like the other two intermittent exotropes, also demonstrated an improvement in controlling his deviation during subsequent cover testing (as reported by the referring clinician).

The fourth subject, patient AP, was an accommodative esotrope who demonstrated zero vectogram fusional ranges (wearing his correction) prior to RDS training. He also exhibited an inability to maintain attention after working for only a few minutes on vectogram tasks. Following RDS convergence training, improved motivation and task attention were noted, as well as increased fusional abilities during

subsequent vectogram sessions. As a matter of fact, all four patients reported enjoying vision training and looking forward to subsequent sessions.

EXPERIMENT 2

The second experimental investigation was done to test whether the improved convergence ranges attained with the four patients in the first study were a result of stimulating convergence rather than just exposure to RDS using an operant conditioning procedure. The second study used normal adult subjects matched on initial convergence ability. One group was given the same type of RDS convergence training as patients in experiment 1. The other group received no increase in convergence demand during operant RDS training. Thus, the RDS stimuli remained at a zero convergence demand.