Comparison of Distance and Near Heterophoria by Two Clinical Methods

Introduction: In the evaluation of binocular function, the heterophoria is an essential measure. Historically, the relationship of the near phoric measure to the far phoria has been a critical finding in the diagnosis of convergence and divergence anomalies. There are a number of ways that the phorias can be measured. It is noted in the literature that different types of phoria measures are statistically similar while other articles report various methods of measures can be quite different. Methods: Each subject was evaluated for binocularity and visual acuity. The Von Graefe and modified Thorington (Howell Card) techniques were performed in a sample of young adult optometry students. Accommodative response was measured clinically following heterophoria testing by Nott retinoscopy. These results were then compared. Results: The Von Graefe technique data was more variable and significantly more exophoric than the Howell Card findings both at distance and near. Conclusions: These findings suggest that you cannot consider the Von Graefe and Howell Card as interchangeable tools to measure a heterophoria. The Von Graefe phoria will, using published criteria, support the diagnoses of convergence insufficiency and of convergence excess more often than the Howell Card.