covariation

In strabismus, covariation refers to a condition where the objective angle (the actual angle of ocular misalignment) and the angle of anomaly (the angle of abnormal binocular visual direction) change simultaneously, while the subjective angle (the perceived angle of misalignment) remains zero. In other words, the patient’s eyes are misaligned, but they perceive the visual world as being properly aligned due to the brain’s adaptation mechanisms. This phenomenon is often observed in long-standing strabismus cases and can pose challenges in treatment and management.