The Relation of Binocular Symptoms with Stereopsis

To determine stereopsis with local (Titmus) and global (TNO) tests in symptomatic and asymptomatic subjects according to induced disparity (crossed or uncrossed).

In this cross sectional study, 80 students of Zahedan University of Medical Sciences who fulfilled the inclusion criteria were randomly selected. At first, refractive error was determined by retinoscopy and then based on the presence of binocular vision symptoms subjects were divided into symptomatic and asymptomatic. The ocular deviation was determined with use of the alternate prism cover test and stereopsiswas determined with TNO and Titmus tests. Data was analyzed in software SPSS.15 using Mann-Withney U, Wilcoxon, Spearman correlation and Fisher’s exact tests.

Mean stereopsis with the TNO test in symptomatic and asymptomatic subjects with crossed disparity was 133.12±70.11 and 76.78±82.57 sec/arc and that with uncrossed disparity was 135.0±67.5 and 83.2±49.7 sec/arc, respectively. Using the Titmus test with crossed disparity the value was 44.3±7.27 and 40.7±3.4 sec/arc and with uncrossed disparity stereopsis was 50.0±12.1 and 40.0±0.0 sec/arc in symptomatic and asymptomatic subjects, respectively. The Mann-Withney U test showed significant difference between stereopsis (with crossed and uncrossed disparity) with symptoms (P<0.05).

Stereopsis is a useful factor in differential diagnosis of individuals with symptomatic and asymptomatic binocular vision that for these purpose the local and global tests can be used, the importance of the global tests is more than local tests. There is no difference between crossed and uncrossed disparity stereopsis in all subjects.