Background and Purpose: Stereoacuity testing is a sensitive indicator of binocular function and is often abnormal in ocular conditions such as strabismus, amblyopia and suppression. It can be valuable in young children, as cooperation and reliability of monocular vision testing often declines during examination. Historic work identified a correlation between stereoacuity and visual acuity in a small cohort of healthy adults. This work is often referenced clinically, however has not been re-evaluated with current acuity charts using logarithmic standards (log minimal angle of resolution – logMAR), in individuals with ocular pathology, or in pre-verbal children.  This study aims to address the current gaps by evaluation the relationship between stereopsis and visual acuity values in those with no ocular pathology, those with ocular pathology, and pre-verbal children utilizing a large retrospective standardized clinic data base for literate subjects and prospective evaluation of a preferential looking method in pre-verbal children. 

Methods: The prospective stream will recruit 255 children aged five and younger to evaluate the testability, sensitivity, and specificity of a preferential looking stereopsis method (PASS 3) compared to current available option (Frisby), and the relationship between stereopsis thresholds and visual acuity on preferential looking testing (Teller). The retrospective stream will review 8265 charts of unique patients at the IWK and measure the relationship between stereopsis thresholds and visual acuity (logMAR) based on acuity of the worse seeing eye and the interocular difference. Both streams will subdivide subjects into normal (no ocular pathology), pathological (documented ocular pathology), and known nil (barrier preventing true clinical stereopsis).

Results: Preliminary findings of PASS 3 (89 participants) show a high testability (92.1%), sensitivity (94.1%), and specificity (83.0%) compared to Frisby (68.5%, 84.6%, and 93.3% respectively) in children aged 5 and under. The data is currently trending with a positive correlation between finer stereoacuity and lower logMAR acuity thresholds in both the prospective and retrospective study groups of normal subjects. 

Conclusion: Preferential looking stereopsis testing (PASS 3) shows greater testability and sensitivity for measuring clinical stereopsis in children compared to the current alternative, with a positive correlation between finer stereopsis and normal acuity for age. This is essential in a pediatric population when examinations can be unpredictable, and stereopsis may be the only reliable measurement obtained. The retrospective review shows preliminary positive correlations between stereopsis thresholds and acuity, which can be important in the context of suspected non-organic vision loss. Data collection and analyses is ongoing 2025-2026.