Screening tests for abnormal alignment. (A through D) The cover test. (A) On simple observation, one eye (the tested eye, which is the patient’s left eye in this illustration) appears to deviate. (B) The uncovered (tested) eye is observed for movement into alignment as the other eye is covered (in this illustration, an exotropia is exposed). This movement into alignment can come from any direction and is generally reproducible on repeat examinations. (C) When the opposite eye is uncovered, the tested eye is observed to return to its original location. (D) When the test eye is the normal eye (which is the patient’s right eye in this illustration), it does not move when the opposite eye is covered or uncovered. (E through G) The cover-uncover test. (E) The tested eye (which is the patient’s left eye in this illustration) is covered. On simple observation, before it is covered, the eye appears to be in alignment. (F) The tested eye is covered for a few seconds. (G) As the cover is rapidly removed, the tested eye is observed for movement back into alignment (in this illustration, an exophoria is exposed).
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