The Orbit, Orbital Contents and Cranial Nerves III, IV and VI

Lecture Objectives Describe the location of the orbit. Make a list of structures making the orbit starting from orbital margin. Define each component. Describe openings into orbital cavity. Define the orbital fascia. Describe muscles of the orbit, their cone arrangement, origin, insertion, nerve supply and their function. Describe the nerves of the orbit, their courses, important relations and their targets Describe blood supply and lymph drainage of the orbit.

The Orbit: Orbital Margin

The Orbit: Orbital Cavity Shape .. Orientation .. Walls ..

Openings into Orbital Cavity Supraorbital notch (foramen) Infraorbital groove, canal, & foramen Nasolacrimal canal Inferior & superior orbital fissures Anterior & posterior ethmoidal foramina

Orbit: Content Eyelid Lacrimal apparatus Eyeball Fascia Extraocular muscles Nerves Blood vessels Fatty tissue

Eye: Fascia Covers the eye Separate the eye from surrounding orbital fat Facilitates movement of eye Pierced by orbital muscles Tubular sheath Attaches to orbital walls Medial & lateral check ligaments Suspensory ligament of the eye

Eye: Muscles Extrinsic muscles Intrinsic muscles Superior rectus Inferior rectus Medial rectus Lateral rectus Superior oblique trochlea Inferior oblique Intrinsic muscles Ciliary m. ‐ parasympathetic Constrictor pupillae of the iris ‐ parasympathetic – Dilator pupillae of the iris ‐ sympathetic

Axes of Eyeball movements

Movements around transverse axis

Movements around vertical and A-P axes

Movements of Eyeball

Nerves of the Orbit

Nerves that Moves the Eyeball Oculomotor (III) Trochlear (IV) Abducens (VI)

Oculomotor Nerve (III) Mixed nerve; principally motor (GSE, GVE) (with proprioseptive) Midbrain (anteriorly) Cavernous sinus Superior and inferior branches Superior orbital fissure

Oculomotor Nerve Nuclei Main motor nucleus (GSE) Location Relations PAG, superior colliculus Connections Cortex, superior colliculus Fibers course Accessory parasympathetic nucleus (Edinger‐Westphal nucleus)(GVE) Main motor nucleus Pretectal nucleus

Pupillary Light Reflex

Oculomotor Nerve (III) The superior branch Superior rectus and levator palpebrae superioris mm. The inferior branch Medial rectus, inferior rectus, and inferior oblique mm. Parasympathetic innervation via the ciliary ganglion to the intrinsic eye muscles Major functions Regulating movements of upper eyelid and eyeball Adjustment of lens for near vision, and constriction of pupil

Oculomotor Nerve (III): Lesion Ptosis (denervation of levator palpebrae) External ophthalmoplegia: Eye look down & out (denervation of extraocular muscles) Diplopia Internal ophthalmoplegia: Dilated, fixed pupil & Paralysis of accommodation Test Asked to move the eye Unable to move up, down, or medial At rest looks down & lateral

Trochlear Nerve (IV) Mixed nerve; primarily motor (GSE) (with proprioceptive) Smallest of the cranial nerves Midbrain* Cavernous sinus Superior orbital fissure Innervate the superior oblique muscle *Only one to arise from the posterior aspect of the brain stem ‐ Decussate and rotate around the brainstem

Trochlear Nerve (IV): Lesion Difficulty to turn eye downward & laterally Diplopia in looking downward

Trochlear Nerve Nucleus Trochlear nerve nucleus (GSE) Location Relations PAG, inferior colliculus, main oculomotor nerve nucleus Connections Cortex, superior colliculus Fibers course

Abducens Nerve (VI) Mixed nerve; primarily motor (GSE) (with proprioceptive) Pons (anteriorly) Cavernous sinus Superior orbital fissure Called abducens because it causes abduction of the eyeball (lateral rotation) Innervates the lateral rectus muscle

Abducens Nerve (VI): Lesion Nerve lesion causes internal strabismus & diplopia Unable to turn eyeball laterally

Abducens Nerve Nucleus Abducent nerve nucleus (GSE) Location Relations 4th ventricle Colliculus facialis Connections Cortex, superior colliculus Fibers course

Nerves of the Orbit Branches of ophthalmic nerve (V1) Frontal nerve Superior orbital fissure Frontal nerve Scalp Branches: Supraorbital & Supratochlear nn. Lacrimal nerve Lateral part of upper eyelid – Carry parasympathetic fibers to lacrimal gland via zygomaticotemporal nerve

Nerves of the Orbit Branches of ophthalmic nerve (V1) Nasociliary nerve‐ Branches: Comunicating branch to ciliary ganglion‐ sensory fibers from short ciliary nn. Long ciliary nn.‐ carry sympathetic fibers (dilator pupillae m.) Posterior ethmoidal n. (ethmoid & sphenoid sinuses) Anterior ethmoidal n. External nasal branch (tip of nose) Infratrochlear n. (medial part of upper eyelid & part of nose)

Nerves of the Orbit

Orbit: Ophthalmic Artery Optic canal Branches of ophthalmic artery Supraorbital a. Supratrochlear a. Central retinal a. Ciliary aa. (short & long) Ethmoidal aa. (anterior & posterior) Lacrimal a. Dorsal nasal a.

Orbit: Ophthalmic Veins ** No lymphatic vessels or nodes in orbit