Vergence orthoptics: validity and persistence of the training effect.

The validity and permanence of orthoptic treatment for vergence deficiencies requires investigation due to the subjective nature of determining success in most clinical cases, i.e., the amelioration of symptoms and increases in vergence ranges. The relation between Risley prism vergences, a subjective measure, and vergence tracking rate, an objective index, is investigated. The course of orthoptics progress is compared in cases of clinical vergence dysfunction. Vergence-deficient control subjects showed no significant change in either index. However, trained subjects demonstrated rapid increases in both indices. The persistence of the training effect was monitored for up to 9 months. No regression was observed in subjects who met all release criteria, but one subject who chose to terminate therapy early showed a slow regression in tracking rate and recurrence of symptoms. These data support the validity of vergence training and increase the plausibility of previous clinical reports of orthoptics success.