Roving eye movements (REMs) describe slow, unhurried, and coordinated movements of both eyes. These movements occur without focusing on any particular object or direction. The movements are often described as undirected or random drifts from side to side, or sometimes in a circular pattern.
What Roving Eye Movements Look Like and When They Are Expected
Roving eye movements are characterized by their slow, smooth, and often horizontal trajectory, though some vertical movements can also occur. They involve both eyes moving together (conjugate movement). However, a slight divergence between the eyes, or exophoria, may also be observed. These movements are distinct from rapid, jerking eye movements (saccades) or rhythmic oscillations (nystagmus).
REMs occur when the brain is not actively processing complex visual information. These movements are a normal occurrence during non-waking states. They are commonly seen during light sleep or rapid eye movement (REM) sleep, where the eyes move back and forth under closed eyelids. Roving eye movements can also be observed in individuals experiencing deep relaxation or altered states of consciousness, such as a deep coma.
Medical Conditions Linked to Roving Eye Movements
REMs can be observed in various medical conditions, particularly when they occur outside of normal sleep or deep unconsciousness. They are frequently associated with metabolic encephalopathy, a condition where systemic metabolic disturbances affect brain function. Examples include severe hypoglycemia (low blood sugar) and hepatic coma (severe liver dysfunction).
REMs can also occur with certain brain injuries or bilateral cerebral infarctions (strokes affecting both sides of the brain). Their occurrence suggests a disruption of higher brain centers, such as the cerebral cortex, while brainstem pathways for eye movement remain intact. The presence of REMs generally indicates that oculomotor and brainstem functions are preserved, even if the patient is unresponsive.
What Roving Eye Movements Can Indicate
Observing REMs provides valuable information for assessing a patient’s neurological status, especially in unconscious or comatose states. The presence of these slow, conjugate eye movements suggests that brainstem pathways controlling eye movement are functional. This indicates that the cause of unconsciousness likely originates from higher brain regions, such as the cerebral cortex, rather than a direct brainstem lesion.
In a comatose patient, REMs can help differentiate between a metabolic or toxic encephalopathy and a structural brainstem injury. If the eyes are moving, it indicates that the oculomotor system can still generate movements, supporting a supratentorial (above the brainstem) cause for coma. Medical staff also utilize other reflexes, such as the vestibulo-ocular reflex (“doll’s eye maneuver”), to further assess brainstem integrity, which aligns with the insights provided by REMs. Therefore, these movements, alongside other neurological signs, aid doctors in diagnosing conditions, predicting outcomes, and monitoring a patient’s neurological state.