Abstract
Purpose :
We investigated effects of monocularly- and binocularly-simulated astigmatism and aniseikonia on stereopsis thresholds. Our purpose was to determine effects of meridian and whether binocular effects are different from monocular effects.
Methods :
Twelve participants with normal binocular vision viewed random dot stereograms through 3D shutter glasses to determine stereoacuity. The task used a four-alternative forced-choice procedure. Astigmatism was induced by placing trial lenses in front of eyes. Ten conditions were used, consisting of zero (no lens) and +2 D cylinders x180, x45 and x90 in front of the right eye, and of the following binocular combinations using +2D lenses: Rx90/Lx90, Rx45/Lx45, Rx180/Lx180, Rx90/Lx180, Rx45/Lx135 and Rx180/Lx90. Aniseikonia was induced by placing magnifying lenses in front of eyes. Thirteen conditions were used, consisting of zero (no lens), 6 and 12% x180, x45 and x90 in front of the right eye, and of the following binocular combinations using 3 and 6% lenses: Rx90/Lx180, Rx45/Lx135, and Rx180/Lx90.
Results :
Stereopsis losses for binocular simulations with parallel axes were the same as for monocular simulations of the same axes (p=0.36). These were dependent strongly on axis (p<0.001) in the order x90 >x45 >x180 (Fig 1). Orthogonal axes had greater effects than parallel axes (e.g. 2Dx90 had a 2.8-fold effect on threshold while orthogonal 2D cylindrical blur had a 4.6-fold effect), with the axis combination of the former having no effect (e.g. Rx90/Lx180 had the same effect as Rx45/Lx135). For induced aniseikonia, splitting magnification between eyes improved stereopsis slightly (11%, p=0.03) and there was no meridional dependence (Fig 2).
Conclusions :
Binocular astigmatic blur affects stereopsis similarly to monocular blur if axes in the two eyes are parallel. However, the effect is much greater if the axes are orthogonal. In aniseikonia, splitting the magnifications between right and left lenses produce a small improvement in stereopsis that is not affected by axis combination. This suggests differences in the way that blur and interocular shape differences are processed during the production of stereopsis.
This is a 2020 ARVO Annual Meeting abstract.