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Comparison of fixation disparity measurements obtained with the Wesson Fixation Disparity Card and the Sheedy
D Dittemore1, J Crum, D Kirschen
1Southern California College of Optometry, Fullerton.
Insights
Fixation disparity measurements from the Disparometer and Wesson Card showed no significant differences when data were analyzed by phoria type (exophoria/esophoria), contrary to previous pooled-data studies.
Area of Science:
- Ophthalmology
- Vision Science
- Optometry
Background:
- Previous research indicated discrepancies between Disparometer and Wesson Card fixation disparity measurements.
- Pooled data analysis in prior studies may have obscured true instrument agreement.
Purpose of the Study:
- To re-evaluate fixation disparity measurements between the Disparometer and Wesson Card.
- To determine if subgroup analysis by phoria type resolves previous discrepancies.
Main Methods:
- Comparative analysis of fixation disparity measurements.
- Data stratified by subject phoria status (exophoria and esophoria).
Main Results:
- Pooled data analysis replicated previous findings of differences.
- Analysis separating subjects by exophoria and esophoria revealed no statistically significant difference between the two instruments.
Conclusions:
- The Disparometer and Wesson Card provide comparable fixation disparity measurements when accounting for individual phoria.
- Subgroup analysis by phoria is crucial for accurate instrument comparison in vision testing.
Abstract:
We compared the fixation disparity measurements obtained with the Disparometer to those of the Wesson Card. Previous studies suggest that the measurements obtained by these two instruments gave different results. The results of previous studies were based on the analysis of pooled data, which may have led to spurious results. Analysis of our data done in this manner (pooled data) revealed the same findings. However, after analysis of the data based on the separation of subjects according to phoria (exophoria/esophoria), no statistically significant difference was found between the measurements obtained with the Wesson Card and those with the Disparometer.