The ophthalmoscope test of the horizontal vestibulo-ocular reflex is a bedside examination that assesses the rotational vestibulo-ocular reflex (VOR). During this test, the examiner visualizes the retina in one of the patient’s eyes using an ophthalmoscope while the patient uses the other eye to fixate on a target directly ahead. The examiner oscillates the head in yaw (turning it from side to side) with small movements, while continuing to visualize the patient’s retina. In a healthy individual, the retina should remain still. In a patient with vestibular weakness, the retina may oscillate with head movement.