Comparison between associated (cross test) and dissociated heterophoria (white and red Maddox cylinder, dark-red glass test)
M. Ball, C. Schmitt, G. Kommerell
Background: Associated heterophoria is a deviation from orthovergence position that results from prism correction of fixation disparity. Since both eyes are presented with fusional contours, the viewing conditions are quite natural. Dissociated heterophoria is defined as a deviation that occurs when no fusional contours are provided, i.e. under unnatural viewing conditions. Neither associated nor dissociated heterophoria are necessarily pathological, but both have been used as clues for prismatic correction in the case of asthenopia. It is unclear whether the methods to determine associated and dissociated heterophoria, mentioned in the title, lead to comparable results.
Methods: Subjects were recruited by examining 100 normally sighted persons, in alternate succession with either the cross test (H.-J. Haase) or the dark-red glass test. All persons with an associated or dissociated heterophoria of more than 0.5 degrees were selected. 48 subjects complied with this criterion. Each of them was subjected to 4 tests, the cross test for associated heterophoria, the white and the red Maddox cylinder tests and the dark-red glass test for dissociated heterophoria. Using Herschel prisms, subjects were asked to continually correct any deviation. Only in the dark-red glass test, subjects were instructed to orally report the uncorrected separation of the images of both eyes. In all 4 tests the measurement was taken after 1 minute.
Results: A preliminary statistical evaluation demonstrated a high correlation between the results obtained with the cross tests on the one hand and the 3 other tests on the other.
Conclusion: In normally sighted persons, there is a high correlation between associated and dissociated heterophoria.
Abteilung Neuroophthalmologie und Schielbehandlung, Universitäts-Augenklinik, Killianstr. 5, D-79106 Freiburg