[Associated heterophoria and the asymmetry of ocular prevalence for stereo images in front of or behind a reference plane].
BACKGROUND
An unequal weighting of the eyes in the directional perception of stereodisparate objects, is referred to as ocular prevalence of the right or left eye, respectively. Between 1962 and 1964 H.-J. Haase developed a valence test for the prismatic correction of heterophoria. He suggested that there would be less prevalence for stereo images presented in front of or behind a reference plane, and that this asymmetry of prevalence may be related to the direction of the associated heterophoria (eso- or exophoria). According to H.-J. Haase, the asymmetry may indicate a fixation disparity with a corresponding shift in retinal correspondence. Hence, the valence test could be an indicator for the prismatic correction of heterophoria.


METHODS
Prevalence was tested in 37 subjects, using three methods: The subjects were asked to describe their perception (1), to make a paper drawing of their perception (2), and to align the position of the stereo images to the central fusion target with a computer-controlled device (3). METHODS 2 and 3 were used to reduce a possible suggestive influence on part of the investigator. The associated heterophoria was determined with the cross test by H.-J. Haase.


RESULTS
Depending on whether the triangular stereo images were presented behind or in front of the reference plane, more or less prevalence was measured (mean values) in the group with exophoria than in the group with esophoria. These results were confirmed with all three methods. The asymmetry of prevalence was correlated with the direction of the associated heterophoria with r = 0.5.


CONCLUSIONS
Statistically, these results confirm Haase's hypothesis of a relation between the asymmetry of ocular prevalence and the direction (eso- or exophoria) of the associated heterophoria. Since this relation holds true only for the group mean value, but not for each individual, the valence test cannot be generally recommended as an adjunct for the prismatic correction of heterophoria.
Opti-school, Studio für Augenglasbestimmung, Freiburg. info@opti-school.de
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Schroth
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Jaschinski
D000328:Adult; D003867:Depth Perception / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted; D005139:Eyeglasses; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012016:Reference Values; D012160:Retina / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013285:Strabismus / Q000503:physiopathology* / Q000628:therapy; D014786:Vision Disorders / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D015357:Vision Disparity / Q000502:physiology*; D014787:Vision Tests; D015348:Vision, Binocular / Q000502:physiology