Abstract
Purpose::
To evaluate the influence of eye dominance on stereopsis. Because the Wirt/Titmus© circles are used routinely in screening for stereopsis (and indirectly evaluating amblyopia), it is important to characterize factors that may modify this test’s results. To our knowledge, the effect of eye dominance on Titmus© stereopsis testing has never been reported.
Methods::
Stereopsis was evaluated in children, aged 3 to 18 years, using the Wirt© circles, presented in the upright (usual) orientation and the inverted (up-side down) orientation. Ocular dominance, alignment, refraction, pathology, sex, age, and presence of Randot© stereopsis were also determined. In all, sixty-five patients presenting to the Henkind Eye Institute (Bronx, NY) with at least 400 sec/arc of stereopsis were included in the study. Due to non-normal data distribution, non-parametric statistical analysis was performed using SPSS® software.
Results::
The Mann-Whitney test showed a significant association between ocular dominance and altered stereopsis in patients with no ocular pathology: OD dominant patients performed better with the circles in the recommended upright orientation (p=0.001), and OS dominant patients performed better with the inverted orientation (p=0.004). The difference in stereopsis between OD and OS dominant children was smaller when using the inverted Titmus© chart. Coexisting ocular pathology (n=15), such as media opacities (3), large tropias (3), retinal degenerations (2), or other pathology (7) substantially reduced this association (p=0.849). Ocular alignment significantly reduced measured stereopsis only in the upright orientation (p=0.001). There was no significant association between eye dominance and ocular alignment, refractive error, age, or sex.
Conclusions::
When presenting the Wirt/Titmus© circles in the manufacturer-recommended (upright) orientation, ocular dominance significantly alters the results of the test. The upright orientation improves perceived stereopsis in OD dominant children and diminishes it in OS dominant children. Measured stereopsis is also diminished in the upright orientation by ocular misalignment. Presenting the circles in an inverted orientation may be the preferred screening method for stereopsis, because it may be less likely to be altered by modifying factors such as eye dominance and alignment.
Keywords: binocular vision/stereopsis • amblyopia • esotropia and exotropia