Musculus levator palpebrae superioris
Elevates the upper eyelid, opening the eye. The primary muscle for keeping the eye open during wakefulness.
Origin: Orbital periosteum dorsal to the optic foramen
Insertion: Upper eyelid (tarsal plate and skin)
Action: Elevates the upper eyelid; opens the palpebral fissure
Innervation: Oculomotor nerve (CN III)
Damage to CN III (from head trauma, EPM, or space-occupying lesions) causes the upper eyelid to droop. May be part of Horner syndrome if sympathetic innervation to the smooth muscle component (Müller'
Damage to CN III (from head trauma, EPM, or space-occupying lesions) causes the upper eyelid to droop. May be part of Horner syndrome if sympathetic innervation to the smooth muscle component (Müller's muscle) is affected. Signs include: Drooping upper eyelid on one side; eye appears partially closed; may be accompanied by miosis (constricted pupil) and enophthalmos in Horner syndrome; facial sweating on the affected side (unique to horses with Horner syndrome).
See the Levator Palpebrae Superioris on our interactive 3D horse model. Open 3D Model