Measurement of paracentral stereopsis using a new method with the binocular open perimeter imovifa® in normal adults

Purpose No method to quantitatively evaluate stereopsis within the 15 degrees visual field has been clinically established. We developed a program to measure paracentral stereopsis and evaluated its feasibility in visually normal participants. Study design Experimental investigation Methods Ten visually normal volunteers with stereopsis of 60 arcseconds or better were included. The Stereo Eccentricity Analysis (SEA) program for stereopsis measurement across the visual field was integrated into the binocular visual field analyzer imovifa (R). Subjects with established binocular stereopsis detected a stereoscopic circular target presented with crossed disparity on random dots at the fovea, 3 degrees, 5 degrees, 10 degrees, and 15 degrees on the 45 degrees, 135 degrees, 225 degrees, and 315 degrees meridians. The subjects performed two tasks for measurement in the periphery: a detection task by pressing the response button when the circular target was perceived and a localization task by tilting a joystick to indicate in which quadrant the circular target was perceived. The duration of the target presentation was 500 ms. Results The stereo thresholds at 0 degrees and 3 degrees did not significantly differ. The thresholds at 10 degrees and 15 degrees were significantly higher than at 0 degrees (P < 0.01). While no inter-individual threshold difference was observed at the fovea, the difference was large at 15 degrees. The stereo thresholds for the detection and localization tasks also did not differ significantly. Conclusion With the SEA program, paracentral stereopsis can be measured and the stereo threshold increases with eccentricity. The SEA program appears to be a feasible clinical method to evaluate paracentral stereopsis.