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The Comparison of Stereopsis with TNO and Titmus Tests in Symptomatic and Asymptomatic University Students

1 January 2011


Introduction: One factor in the evaluation of binocular vision is the measurement of stereopsis. Several methods are available for this purpose. The most common procedures are anaglyphic (with use of red-green filters) and vectographic (with use of polarized filters) procedures. The purpose of this study is determination of stereopsis with local (Titmus) and global (TNO) tests in symptomatic and asymptomatic subjects with respect to type of disparity (crossed and/or uncrossed) in exophoric and esophoric subjects.

Methods: In this cross-sectional study, 174 randomly selected students of Zahedan University of Medical Sciences that met inclusion criteria served as subjects. Subjects were divided into symptomatic and asymptomatic groups according to the presence or absence of binocular vision symptoms. Dissociated heterophoria was determined with use of the alternate prism cover test and stereopsis with TNO and Titmus tests. After data collection, data were analyzed in SPSS.17 software using the Mann-Withney U, Wilcoxon and receiver operating characteristic (ROC) curve.

Results: The results of this study showed that the mean stereopsis with TNO test in symptomatic and asymptomatic subjects was 133.1 ± 68.6 and 76.7 ± 81.9 sec arc, respectively, in subjects with crossed disparity, and 135.0 ± 66.0 and 83.2 ± 49.3 sec arc, respectively, with uncrossed disparity. With Titmus test, mean stereopsis with crossed disparity in symptomatic and asymptomatic subjects was 44.3 ± 7.1 and 40.7 ± 3.3 sec arc, respectively, and with uncrossed disparity 50.0 ± 11.8 and 40.0 ± 0.0 sec arc, respectively. The Mann- Whitney U test showed a statistically significant difference in stereopsis (with crossed and uncrossed disparity) between the two groups (p0.05). The best cut-off points for distinguishing between symptomatic and asymptomatic subjects with the TNO and Titmus stereo tests were determined to be 90 and 45 seconds of arc, respectively.

Conclusion: Stereopsis is a useful factor in distinguishing between symptomatic and asymptomatic individuals. For that purpose, a global test was more useful than a local test. Also, there was no any difference between crossed and uncrossed disparity stereopsis in symptomatic and asymptomatic subjects.


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