Musculus rectus lateralis
The lateral rectus originates from the common tendinous ring around the optic foramen and inserts on the lateral sclera of the eyeball. Its action is to abduct the eyeball (rotate it temporally). It is innervated solely by the abducens nerve (CN VI). The abducens nerve also supplies the retractor bulbi.
Origin: Common tendinous ring around the optic foramen
Insertion: Lateral sclera of the eyeball
Action: Abducts the eyeball (rotates temporally)
Innervation: Abducens nerve (CN VI)
Isolated dysfunction is uncommon. Damage to the abducens nerve can cause inability to abduct the eye. More often evaluated as part of a full neurologic or ophthalmic examination.
## 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 me
Abnormal eye position or movement after trauma should be checked by a veterinarian.
## 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. Signs include: eye deviated medially; inability to move the eye laterally; head turn to compensate; possible diplopia-related behavior
Isolated dysfunction is uncommon. Damage to the abducens nerve can cause inability to abduct the eye. More often evaluated as part of a full neurologic or ophthalmic examination.
Abnormal eye position or movement after trauma should be checked by a veterinarian.
See the Lateral Rectus on our interactive 3D horse model. Open 3D Model