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Abstract
Previous studies have found the modified Thorington lesi and the Howell phoria card test ro be more repeatable than the von Graefe tesi. Another potentiell way io assess the value of a lest could be to con-elate test results with the level of svinptoms. Near dissociated phorias were measured with the modified Thorington, Howell phoria card, and von Graefe procedures with 50 subjects between the ages of ift and 35. The von Graefe test was performed with two different targets, thus making a total of four different phoria tests. All testing was performed using a phoropter. Test findings were correlated with symptom scores from a questionnaire. The means on the four tests ranged from 2. 7Δexo to 3.7Δ exo. Correlations of phoria findings with symptom scores were not statistically significant for any of the four tesis in subjects with exophoria. In a small number of subjects with esophoria, significant correlations were found between phoria and symptom scores for the modified Thorington fes! and the Howell phoria card tesi bui not with the von Graefe test. The modified Thorington test and the Howell phoria card tesi were more repeatable than the von Graefe test.
Key Words
binocular vision, clinical tests, heterophoria. phoria, repeatability, validity, vergence
INTRODUCTION
Dissociated phoria testing is an important part of the clinical evaluation of binocular vision. Probably the most commonly used subjective dissociated phoria test is the von Graefe test.1,2 Another common lest using a tangent scale and a Maddox rod over one eye is referred to as the modified Thoringion test.3-4 Studies have consistently found the modified Thorington test to be more repeatable than the von Graefe test.5'" An additional test, attributed to Prentice.'' uses prism dissociation of a tangent scale. One study reported the repeatability of that test using a card marketed by Howell to be comparable to that for the modified Thorington."
To be of most value to the practitioner, clinical tests should be both reliable (repeatable) and valid. Comparisons of the repeatability of von Graefe and modified Thorington dissociated phoria lests have been examined in previous publications. but to our knowledge, comparisons of the validity of these tests have not been done. One method whereby the validity of a tesi might be assessed could be...