The course and effect of visual training on the vergence system.
The effect of a variety of vergence training procedures on the visual system of 35 asymptomatic young adults with normal binocularity was evaluated. The visual training took place on the weekdays of three consecutive weeks. Vergence ranges were measured before the study began and at the end of the 3-week period. Subpopulations were evaluated at one week and at 6 months to document further the course of the effects. Positive fusional vergence training significantly increased the vergence ranges after 1 week of training; a greater effect was measured after 3 weeks. The vergence capability was found to have decreased 6 months later, but the effects of the training were still apparent. Negative fusional vergence training was less effective; however, significant increases were demonstrable after 3 weeks of training. The phorias the accommodative amplitude were not affected by the orthoptics. We conclude that relatively short periods of training can provide long-lasting increases in the vergence ability of a group of binocular normals. The implications of such findings relative to possible neural control mechanisms and clinical visual training situations are discussed.