Evaluation of a New Distance Randot Test in Normal and Strabismic Patients

Abstract

Abstract: : Purpose: A new Distance Randot test was designed as a ‘distance version’ of the Randot near stereoacuity test, specifically to assess binocularity in strabismic patients with differences in distance and near angle of deviation and in patients whose alignment decompensates when dissociated. Here we compare the Distance Randot test to established measures of stereoacuity. Methods: Distance Randot (with vectographic random dot targets subtending 800", 200" and 60"), distance Frisby–Davis 2 (a free space test of real depth; FD2), and near Preschool Randot stereoacuity were assessed in 17 normal children (ages 4–14 y), 8 normal adults (ages 23–36 y) and 127 nonamblyopic patients with a variety of strabismic conditions (ages 4–85 yr). For each test, stereoacuity was defined as the smallest disparity where 2 of 3 targets were correctly identified. Concordance among stereotests was evaluated for nil, 800–400", 200–100" and 80–20" categories. After completing the stereotests, strabismus was measured with the simultaneous prism and cover test and the alternate prism and cover test. Results: All normal children and adults, and 5 of 6 orthophoric patients, passed the Distance Randot test at 60" or 200", similar to their performance on the distance FD2 and near Preschool Randot. In these normal subjects, concordance between the Distance Randot and FD2 was 21/22 (95%) and between the Distance Randot and near Preschool Randot was 26/31 (84%). For strabismic patients, concordance was lower; 65/114 (57%) between Distance Randot test and the distance FD2 and 69/123 (56%) between the Distance Randot test and near Preschool Randot tests. Distance Randot stereoacuity is more sensitive to intermittent strabismus, differences in near vs. distance angle of deviation, dissociation by polarizing filters, and/or differences in peripheral fusion cues. Conclusions: In normal subjects the Distance Randot test yields similar stereothresholds to established methods. In strabismic subjects, the greater discordance between the Distance Randot and other tests may reflect the desired properties of sensitivity to disruptions in binocular vision. The Distance Randot test provides a useful tool in measuring distance stereoacuity in patients with and without strabismus. Clinically, the Distance Randot test may be useful in monitoring the progression of intermittent exotropia to guide the timing of intervention.

Keywords: binocular vision/stereopsis • strabismus • esotropia and exotropia