Comparison of Wesson and modified Sheedy fixation disparity tests. Do fixation disparity measures relate to normal...

A new fixation disparity measuring device, the Wesson Fixation Disparity Card, is compared with the modified Sheedy Disparometer. Twenty-eight subjects were divided into normal and abnormal categories of binocular status determined by classical clinical techniques rather than on patients' subjective symptomatology. Fixation disparity curves were generated on all subjects using both instruments. There were significant differences between the two instruments. Neither instrument was able to distinguish between normal and abnormal subjects but, over a five day period, each instrument produced repeatable results. The validity of fixation disparity measurements using either instrument on naive observers, especially children, is questioned.