Musculus rectus ventralis
The ventral rectus (inferior rectus) is one of the four rectus extraocular muscles. It originates from the common tendinous ring around the optic foramen and inserts on the ventral sclera of the eyeball. Its action is to rotate the eyeball ventrally (looks down). It is innervated by the oculomotor nerve (cranial nerve III).
Origin: Common tendinous ring around the optic foramen
Insertion: Ventral sclera of the eyeball
Action: Rotates the eyeball ventrally (looks down)
Innervation: Oculomotor nerve (CN III)
Isolated injury is uncommon. Relevant in evaluations of extraocular muscle function and after orbital trauma.
## Overview Paralysis of cranial nerve III (oculomotor nerve) produces a combination of signs because the nerve supplies multiple extraocular muscles plus the pupil constrictor and eyelid elevator. T
Persistent abnormal eye position or movement after trauma should be evaluated.
## Overview Paralysis of cranial nerve III (oculomotor nerve) produces a combination of signs because the nerve supplies multiple extraocular muscles plus the pupil constrictor and eyelid elevator. Typical findings include ventrolateral strabismus (eye positioned down and out), ptosis (drooping upper eyelid), and a dilated pupil that responds poorly to light. Causes include trauma, brainstem disease, and space-occupying lesions. ## Causes Trauma, equine protozoal myeloencephalitis, brainstem masses, or polyneuritis. The evidence for frequency of each cause in horses is limited. ## Diagnosis Neurologic and ophthalmic examination demonstrating the characteristic triad of strabismus, ptosis, and mydriasis. Further diagnostics (cerebrospinal fluid analysis, imaging) seek the underlying lesion. ## Treatment Directed at the primary disease when identified. Supportive care protects the cornea if eyelid function is impaired. Specific nerve recovery is often incomplete. ## Recovery and Prognosis Guarded. Some traumatic or inflammatory cases improve partially; permanent deficits are common. ## Prevention None specific. Signs include: eye positioned down and out; drooping upper eyelid; dilated pupil with poor light response; possible vision impairment
Isolated injury is uncommon. Relevant in evaluations of extraocular muscle function and after orbital trauma.
Persistent abnormal eye position or movement after trauma should be evaluated.
See the Ventral Rectus (Inferior Rectus) on our interactive 3D horse model. Open 3D Model