Methods for measuring the proximity-fixation-disparity curve.
The reliability and validity of new tests of fixation disparity were investigated as a function of viewing distance (100, 60, 40, and 30 cm). The 'nonius offset card' presents a set of paired dichoptic nonius (vernier) lines with different offset simultaneously: the subject has to indicate the coinciding lines. The 'computer test' uses a psychophysical procedure that presents one pair of nonius lines sequentially with varying offset; the effect of the number of short-term nonius test trials is investigated. As a reference, the Mallett unit and the Sheedy disparometer were used. Despite different group means, the methods had significant test-retest correlations and inter-correlations, as tested at 40 cm. All methods showed an increase in exo fixation disparity as the viewing distance was shortened; the slope of this proximity-fixation-disparity curve, however, was different between the nonius offset card and the computer test.
Jaschinski
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Institut für Arbeitsphysiologie, Dortmund, Germany. jaschinski@ifado.de
D003196:Computer Graphics; D005403:Fixation, Ocular / Q000502:physiology*; D006801:Humans; D009907:Optometry / Q000379:methods; D011601:Psychophysics; D015203:Reproducibility of Results; D015357:Vision Disparity / Q000502:physiology*