Objective: The purpose of this study is to determine the effect of latent strabismus on stereoacuity.

Methods: Stereoacuities of normal individuals, ranging in age from 18 to 35 years, were measured using the TNO or Titmus tests. The study population was divided into 2 groups regarding the achievement of the accepted excellent stereoacuity threshold of 30 arcseconds (group A) or not (group B). The relationship between latent deviation angles and stereoacuity levels were evaluated.

Results: Latent deviation angles ranged from 0 to 35 prism diopters (PD). Both TNO (r=0.380 p=0.002) and Titmus (r=0.306 p=0.015) stereothresholds tended to increase as the latent deviation angles increased. Group A included 27 participants who had either exophoria (18) or orthophoria (9), and the mean deviation angle of this group was 3.07±3.26 PD. Group B included 36 participants, 28 of whom had exophoria, three had esophoria, and the remaining five had orthophoria. The mean angle of deviation in group B was 6.50±6.92 PD. This value was statistically higher than the mean deviation angle in group A (p=0.012). Though none of the esophoric participants achieved excellent stereoacuity, the distribution of the deviation types did not cause any difference between the groups (p=0.077). The mean age of group A was found to be higher than that of group B (p=0.006).

Conclusion: Latent deviation can mask true stereosensitivity potentials of subjects to some extent during the stereotesting procedure.