## Overview Paralysis of cranial nerve VI (abducens nerve) denervates the lateral rectus muscle, so the eye cannot abduct. Unopposed action of the medial rectus pulls the globe medially, producing medial strabismus (esotropia). The horse may turn its head to reduce double vision. Causes include trauma, brainstem lesions, and inflammatory disease. ## Causes Trauma, equine protozoal myeloencephalitis, or other brainstem pathology. Isolated abducens paralysis is uncommon. ## Diagnosis Observation of medial deviation of the globe that persists or worsens when the head is turned. Full neurologic examination looks for accompanying signs. ## Treatment Treatment of the underlying cause. The strabismus itself is managed supportively; surgical correction is rarely performed in horses. ## Recovery and Prognosis Variable. Some cases improve if the primary disease resolves; permanent medial strabismus is possible. ## Prevention None specific.
eye deviated medially; inability to move the eye laterally; head turn to compensate; possible diplopia-related behavior
## Overview Paralysis of cranial nerve VI (abducens nerve) denervates the lateral rectus muscle, so the eye cannot abduct. Unopposed action of the medial rectus pulls the globe medially, producing medial strabismus (esotropia). The horse may turn its head to reduce double vision. Causes include trauma, brainstem lesions, and inflammatory disease. ## Causes Trauma, equine protozoal myeloencephalitis, or other brainstem pathology. Isolated abducens paralysis is uncommon. ## Diagnosis Observation of medial deviation of the globe that persists or worsens when the head is turned. Full neurologic examination looks for accompanying signs. ## Treatment Treatment of the underlying cause. The strabismus itself is managed supportively; surgical correction is rarely performed in horses. ## Recovery and Prognosis Variable. Some cases improve if the primary disease resolves; permanent medial strabismus is possible. ## Prevention None specific.
eye deviated medially; inability to move the eye laterally; head turn to compensate; possible diplopia-related behavior