New measures of fixation disparity in the diagnosis of binocular oculomotor deficiencies.
Two new measures of fixation disparity have been successfully used to evaluate the occurrence of binocular oculomotor deficiencies under (normal) viewing conditions with no interposed prisms. They are the threshold for the perception of misalignment between briefly presented dichoptic nonius lines and the SD of this threshold. The effectiveness of these new measures of fixation disparity for diagnosing binocular oculomotor deficiencies, which are symptomatically manifested as asthenopia, was found to surpass the diagnostic effectiveness of two measures of fixation disparity in current use: the mean amount of fixation disparity at the point where there are no prisms before the eyes and the slope of the fixation disparity curve near this point. The high diagnostic effectiveness of the new measures of fixation disparity, which are related to the spread of the fixation disparity, suggests that the binocular oculomotor deficiency underlying asthenopia is in essence an inaccurate and unstable alignment of the two eyes.
D001248:Asthenopia / Q000175:diagnosis*; D005403:Fixation, Ocular; D006801:Humans; D009801:Oculomotor Muscles / Q000503:physiopathology*