PURPOSE. According to the progression hypothesis, small angle strabismus (SAS) can lead to large angle squints. The prevalence of SAS is not well established. However, strabismus is a prevalent and significant vision disorder and the identification of SAS is important. Therefore, the purpose of this study is to determine the effectiveness for each of 9 clinically used tests to correctly categorize abnormal visual performance in SAS. Tests were chosen from four categories: (1) corneal reflex, (2) fusion, (3) stereopsis, (4) suppression on the basis of common usage in detecting strabismus. METHOD. Thirty small angle strabismics (ocular deviations of 10 prism diopters or less) ranging in age from 10 to 68 years were tested on each of the 9 tests according to a standardized protocol. The tests used were corneal reflexes by Hirschberg test and photorefraction, fusion by Bagolini procedure and anaglyphic Worth 4 dot test, stereoacuity by BVAT, Lang, Randot, RDE, and Titmus stereotests, and suppression by the 4 BO prism test. Tests were completed in a variable balanced order. Sensitivity (SENS), Specificity (SPEC), Positive Predictive Value (PPV), and Negative Predictive Value (NPV) were determined by comparing each strabismic''s performance on each of the 9 tests to those obtained with the cover/uncover test.
RESULTS. For each of the four test categories, SENS, SPEC, PPV and NPV values are reported respectively: corneal reflex (0.0%, 100%, 0.0%, 100%); fusion (64.0-65.4%, 66.6%-100%, 94.4%-100%, 15.4%-18.2%), stereopsis (3.7%-95.8%, 50.0%-100%, 87%-100%, 13.3%-60.0%), suppression (85.2%, 50.0%, 95.8%, 20.0%).
CONCLUSIONS. Use of selected stereotests increases the effectiveness of identifying SAS related anomalies.