AN31.1-5 | Orbit — Glossary

Common tendinous ring at the orbital apex from which the four rectus muscles originate; surrounds the optic canal and part of the superior orbital fissure

Fibrocartilaginous pulley at the superomedial angle of the orbit through which the superior oblique tendon passes, changing its direction of pull

The seventh extraocular muscle that elevates the upper eyelid; supplied by CN III (superior division) and contains Muller's muscle (sympathetic)

Smooth muscle fibres within the LPS supplied by the sympathetic nervous system; paralysis causes the partial ptosis of Horner's syndrome

Motor nerve to most extraocular muscles (SR, IR, MR, IO, LPS) and parasympathetic supply to sphincter pupillae and ciliary muscle via the ciliary ganglion

Motor nerve to the superior oblique; the only cranial nerve that exits from the dorsal brainstem and has the longest intracranial course

Motor nerve to the lateral rectus; vulnerable to raised intracranial pressure due to its long course over the petrous apex

Sensory branch of the trigeminal nerve supplying the orbit, upper eyelid, forehead, and nose; divides into lacrimal, frontal, and nasociliary branches

Parasympathetic ganglion in the orbit that relays fibres from CN III inferior division to the sphincter pupillae and ciliary muscle via short ciliary nerves

Branch of the ophthalmic artery that enters the optic nerve to supply the inner retinal layers; an end artery whose occlusion causes sudden visual loss

Principal venous drainage of the orbit, draining posteriorly into the cavernous sinus; valveless, allowing retrograde spread of facial infections

Clinical triad of miosis, partial ptosis, and anhidrosis caused by interruption of the three-neuron sympathetic pathway to the eye at any level

Sympathetic cell body cluster in the lateral horn of the spinal cord at C8-T2 forming the first synapse in the oculosympathetic pathway

Largest sympathetic ganglion at C2-C3 level where 2nd order neurons synapse; postganglionic fibres travel along the internal carotid to the eye

Almond-shaped gland in the superolateral orbit producing tears; secretomotor supply via CN VII parasympathetic fibres relayed through the pterygopalatine ganglion

Duct draining tears from the lacrimal sac to the inferior meatus of the nasal cavity; obstruction causes epiphora (watering eyes)

Misalignment of the eyes (squint); may be paralytic (from cranial nerve palsy) or non-paralytic (concomitant)

Drooping of the upper eyelid; complete in CN III palsy (LPS paralysis), partial in Horner's syndrome (Muller's muscle paralysis)

Region around the nose and upper lip where facial infections can spread via valveless ophthalmic veins to the cavernous sinus

Life-threatening venous thrombosis of the cavernous sinus, potentially caused by facial infections or orbital cellulitis spreading via valveless veins

Berry aneurysm at the junction of ICA and PCA; classically presents with pupil-involved CN III palsy as a neurosurgical emergency

Parasympathetic ganglion in the pterygopalatine fossa that relays secretomotor fibres from CN VII to the lacrimal gland, nasal glands, and palatal glands