Comparison of the Effect of Different Types of Experimental Anisometropia on Stereopsis Measured with Titmus, Randot and TNO Stereotests

Purpose: To assess the effect of experimental anisometropia and monovision on stereopsis using the Titmus, Randot, and TNO stereoacuity tests. Methods: Sixty adult volunteers were enrolled in the present study. Four different types of anisometropia—myopia, hyperopia, and astigmatism (both 90° and 45°)—were induced by placing trial lenses over the dominant eye (from 3 to 1 D). Stereoacuity was measured using the Titmus, Randot, and TNO tests. Results: In all the anisometropia types, stereopsis deteriorated with increase in anisometropia in the three stereoacuity tests performed (P < 0.001). The largest decrease in stereopsis was attributed to 3 D myopic anisometropia—6.51 ± 2.10, 6.59 ± 2.35, and 7.36 ± 1.89 arc seconds in Titmus circles, Randot circles, and TNO, respectively. Minimal change in stereopsis was observed in 1 D astigmatism of 45°. Conclusion: Any type of anisometropia may reduce stereoacuity; this reduction is most noticeable with myopic anisometropia, especially in the TNO test, probably due to the lack of monocular cues.