Casual Fixation Disparity Testing: Direct Comparison Of The Saladin Near Point Card With And Without Fusion Contours.

Background: The purpose ofthis study was to investigate whether the multiple fusion
contours found on the Saladin Near Point Balance Card (SNPC) have an effect on the
patients horizontal fixation disparity curve. Methods: Readings were taken from 32 young adults with best corrected near visual acuity in place resulting in 20/20 vision. A modified Thorington was used to rule out any dissociated phoria. Casual fixation disparity (FD) measurements were taken through forced vergence demands of 0, 4BI, and 4BO prism diopters simultaneously from an original SNPC and one designed to hide all distractions. Results: Eso fixation disparity was more evident without the multiple fusion contours when measured with 4BI prism than compared to the original SNPC. 0 and 4BO measurements revealed similar exo FD reading with both cards. Conclusion: The data suggests that the vergence system is less able to withstand eso prismatic stress when the multiple fusion contours are absent. Due to the flat spot in the fixation disparity curve measurements with > 4BO prism may be needed to put the system under stress to determine if the vergence system will be able to handle the stress in the exo direction.