Investigation of Maximum Disparity and Stereopsis
Helen Davis, DBO(T); David Buckley, PhD
University of Sheffield
Introduction: Previous research has been carried out into relating minimum disparity stereoacuity to the control of an intermittent deviation. This study measured maximum disparity and compared this to the fusion range which is also used to asses control.
Methods: Random-dot stereograms were viewed using crystal shutter goggles and the participants viewed a central circle stimulus. This circle either advanced or receded and either moved gradually or in static increments. When fusion was lost, the maximum stereoacuity was recorded in seconds of arc. The Prism Fusion Range was measured both base in and base out. A TNO stereotest was also performed to threshold.
Results: 21 participants were recruited all with good visual acuity and normal binocular single vision. The mean value for the advancing target was 206.7 seconds of arc for static disparity and 259.98 for gradually increasing disparity. For the receding target the mean was 128.52 for static and 157.38 for gradual. The ANOVA demonstrated a significant difference between advancing and receding stimuli p<0.05 as was the difference between static and gradual presentation p<0.05
There was no correlation between maximum disparity achieved and the TNO or Prism Fusion Range results.
Discussion: These results provide normative data for maximum disparity achieved. The reasons for the differences found will be discussed
Conclusion: This method of assessment warrants further exploration in relation to heterophoria and intermittent deviations