Sanfilippo S, Clahane AC.

The effectiveness of orthoptics alone in selected cases of exodeviations: the immediate results and several years later.

American Orthoptic Journal, 20: 104-117, 1970.

Sanfilippo and Clahane designed a prospective study of the results of orthopic therapy for intermittent exotropia. 64.5% reported cured, 9.7% reported improvement, 9% reported fair. Subsequently after 5 years, 52% remained cured, 32% remained improved.