13-orbit & Eye

~ ~ ~ ORBIT & EYEBALL ~ ~ ~ Dr. Cunningham

Structure

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

Bone

Transmission

Communication

Supraorbital Foramen

Frontal

Supraorbital BV-N's

forehead

Infraorbital Foramen

Maxilla

Infraorbital BV-N's

under the eye

Optic Canal

Lesser Wing

Optic Nerve (II) Ophthalmic Artery III, IV, V1, VI Opthalmic Vein

Middle Cranial Fossa Middle Cranial Fossa

Superior Orbital Fissure

b/t Greater & Lesser Wings

Inferior Orbital Fissure

b/t Greater Wing & Maxilla

Infraorbital BV-N's

Pterygopalatine Fossa

Anterior & Posterior Ethmoidal Foramina

b/t Frontal & Ethmoid

Ethmoidal BV-N's Nasociliary Nerve

Ethmoidal Air Sinuses

Nasolacrimal Canal

Lacrimal

Nasolacrimal Duct

Nasal Cavity

Zygomatic

Zygomaticofacial BV-N's Zygomaticotemporal BV-N's

Zygomaticofacial Canal Zygomaticotemporal Canal

Zygomatic Canal

MARGINS - superior = frontal - inferior = zygomatic + maxilla - lateral = zygomatic - medial = maxilla

WALLS - roof = frontal - floor = zygomatic + maxilla - lateral = zygomatic - medial = maxilla, lacrimal, ethmoid, a tiny part of the palatine bone - posterior = sphenoid greater & lesser wings

CONTENTS • eyeball • optic nerve - lacrimal gland - extraocular muscles - BV-N’s - protective fat

RELATIONSHIP TO CRANIUM - superior = anterior cranial fossa, brain’s frontal lobe - inferior = maxillary sinus - posterior = middle cranial fossa, brain’s temporal lobe - medial = nasal cavity - lateral = temporal fossa

• periorbita - lining of the orbit, in b/t the bone and fat - continuous w/ periosteal layer of the dura & periosteum outside the skull - extends into upper & lower eyelids - thickens to become the common tenidinous ring

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Muscle

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05 Innervation

Origin

Insertion

Action

Lateral Rectus

lateral tendinous ring

lateral aspect of eyeball behind sclerocorneal jxn

aBduction

Abducens (VI)

Medial Rectus

medial tendinous ring

medial aspect of eyeball behind sclerocorneal jxn

aDduction

Oculomotor (III)

Superior Rectus

superior tendinous ring

superior aspect of eyeball behind sclerocorneal jxn

elevation aDduction

Oculomotor (III)

Inferior Rectus

inferior tendinous ring

inferior ascpect of eyeball behind sclerocorneal jxn

Oculomotor (III)

superomedial tendinous ring

posterior superior lateral aspect of the eyeball sclera

orbital floor near the posterior larimal crest

posterior inferior lateral aspect of the eyeball sclera

depression aDduction depression aBduction intorsion elevation aBduction extorsion

superior tendinous ring orbital roof

most in skin of upper lid some in tarsus of upper lid

opens upper lid voluntarily opens upper lid involuntarily

Superior Oblique

Inferior Oblique

Lev. Palpebrae Superioris

ADDUCTORS - superior rectus - inferior rectus - medial rectus

ABDUCTORS - superior oblique - inferior oblique - lateral rectus

ELEVATORS - superior rectus - inferior oblique

DEPRESSORS - inferior rectus - superior oblique

Trochlear (IV)

Oculomotor (III)

Oculomotor (III) sympathetic fibers

ROTATORS - superior rectus - superior oblique - inferior rectus

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Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

SUPPLEMENTARY NOTES FROM LECTURE • Common Tendinous Ring - the thickened part of the periorbita - surrounds the optic canal and superior orbital fissure - origin of attachment for the 4 rectus muscles - what passes thru it = Oculomotor, Abducens, Nasociliary nerves • Ptosis = drooping of the eyelid (in reference to the Levator Palpebrae Superioris muscle) - damage to just the sympathetic fibers  partial ptosis - damage to the entire Oculomotor Nerve  complete ptosis - The eye can move on 3 different axes - vertical axis = adduction + abduction - horizontal axis = elevation + depression - anterior-posterior axis: • intorsion = corneal 12:00 moves medially • extorsion = conreal 12:00 moves laterally

the anterior-posterior axis of the eyeball differs from that same axis of the orbit by 22°

MOTOR NERVES TO EXTRAOCULAR MUSCLES • Oculomotor Nerve (III) - enters the orbit thru the Superior Orbital Fissure, passes thru the Tendinous Ring  also carries a preganglionic parasympathetic component that - originated in the Edinger-Westphal nucleus in the Midbrain - synapses at the Ciliary Ganglion - postganglionic fibers hitch-hike w/ Short Ciliary Nerve of V1 to go to innervate pupil constriction & accommodation - Superior Branch supplies… ○ Superior Rectus ○ Levator Palpebrae Superioris - Inferior Branch supplies… ○ Inferior Rectus ○ Inferior Oblique ○ Medial Rectus • Trochlear Nerve (IV) - enters orbit thru the Superior Orbital Fissure NOT within the cone of muscles ○ Superior Oblique muscle ONLY • Abducens Nerve (VI) - enters orbit thru the Superior Orbital Fissure within the cone of muscles ○ Lateral Rectus muscle ONLY

SENSORY NERVES not considered a true cranial nerve b/c it is an extension from the brain

• Optic Nerve (II) – special sensory

- leaves the middle cranial fossa thru the Optic Canal

• Ophthalmic Nerve (V1) – general sensory

- leaves the middle cranial fossa thru the Superior Orbital Fissure

 Frontal Nerve (superior wall) ○ Supraorbital = supplies skin of the middle upper eyelid, forehead, scalp ○ Supratrochlear = supplies skin of the medial upper eyelid, forehead, scalp  Lacrimal Nerve (lateral wall) = supplies skin of the lateral upper eyelid  picks up hitchhiking postgang. parasympathetic fibers from the Greater Petrosal Nerve (originated from VII) Production of tears…

as well as postgang. sympathetic fibers from the Deep Petrosal Nerve (originated from Internal Carotid Plexus). Both of them came thru the Pterygoid Canal to become the Vidian Nerve in the Pterygopalatine Ganglion, then traveled w/ the Zygomaticotemporal Nerve (V2) and sent a communicating branch to the Lacrimal Gland

 Nasociliary Nerve (medial wall) ○ Ganglionic branches  Ciliary Ganglion ○ Long Ciliary branches

- supplies general sensation to the eyeball - supplies postganglionic sympathetic innervation  pupil dilation

○ Anterior & Posterior Ethmoidal nerves = supplies the anterior & posterior ethmoidal air cells ○ Infratrochlear nerve = supplies skin of the medial angle of upper eyelid

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CRANIAL GANGLIA - there are 4 parasympathetic “relay stations” in the head, each attached to a branch of the Trigeminal Nerve

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

• sensory fibers = originating from branches of the Trigeminal Nerve  passes thru ganglion w/o synapsing • sympathetic fibers = originates from Superior Cervical Ganglion  Carotid Plexus  passes thru ganglion w/o synapsing • parasympathetic fibers = originate from its own special nucleus within the brainstem  then synapse in the ganglia they travel along w/ cranial nerves III, VII, IX CILIARY GANGLION = located in the orbit - incoming fibers… • sensory fibers = from the Long Ciliary Nerve  Nasociliary  Ophthalmic V1 • postganglionic sympathetic fibers = from the Carotid Plexus  Superior Cervical Ganglion • parasympathetic fibers = traveling w/ the Oculomotor Nerve (III) - outgoing fibers… • Short Ciliary Nerve provides… ○ general sensory to the eyeball ○ sympathetic branches for pupil dilation ○ parasympathetic branches for pupil constriction & accomodation  By the way… what about the Long Ciliary Nerve??? • these are the same sensory & sympathetic fibers as the Short Ciliary Nerve But DO NOT pass thru the Ciliary Ganglion (they take a longer route) ○ general sensory to the eyeball ○ sympathetic branches ○ NO PARASYMPATHETIC FIBERS! • Horner’s Syndrome - caused by a lesion in the cervical sympathetic trunk - permanent constriction of the pupil due to paralysis of the Pupillary Dilator muscle (receiving no sympathetic innervation) - partial ptosis (dropping eyelid) due to paralysis of the Levator Palpebrae Superioris muscle (receiving no sympathetic innervation) - no sweating on the ipsilateral side of the neck and face Dr. Singh’s drawing of Long & Short Ciliary Nerves

OPHTHALMIC ARTERY - originates from the Internal Carotid Artery, travels w/ Optic Nerve to leave the middle cranial fossa, exits thru the Optic Foramen to enter the orbit - gives off branches that parallel the branches of the Ophthalmic Nerve…  Central Artery of the Retina - this is the most important branch that we need to know - it is an “end artery,” meaning there is no anastomosis to any other vessels - occlusion (blockage) will result in blindness because there are no other alternative routes - travels in the middle of the Optic Nerve

OPHTHALMIC VEINS - passes thru the Superior Orbital Fissure  Superior Ophthalmic Vein  Cavernous Sinus • Facial Vein (no valves, one-way direction)  Angular Vein  Inferior Ophthalmic Vein  Pterygoid Plexus

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EYEBALL

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

ANATOMY OF THE EYELIDS / PALPEBRAE (from Vital Book) • superior palpebral margin = covers the superior 1/5 of the iris when the lids are open • inferior palpebral margin = covers the inferior 1/5 of the iris when the lids are open • palpebral commissures = the lateral and medial jxns of the upper and lower lids • palpebral fissure = the opening between the upper and lower lids • eyelashes (cilia) w/ sebaceous ciliary glands (Glands of Zeis) -- “STYE” = infected ciliary glands • palpebral conjunctiva = the skin of the inner lining of the lids that reflects up on to the anterior surface of the eyeball • bulbar conjunctiva = the skin on the eyeball’s sclera, NOT the cornea • conjunctival fornices = where the palebral conjunctiva of the lid reflects onto the bulbar conjunctiva of the eyeball • conjunctival sac = the vestibule where tears accumulate • superior + inferior papillae = small raised bumps at the jxn of the ciliated and hairless margins • punctum = the openings of the papillae that soaks up excess tears  canaliculi  lacrimal sac sitting in the lacrimal fossa • lacus lacrimalis w/ caruncle = the small raised red triangular part of the medial angle • plica semilunaris = the fold at the medial angle of the eye that separates the white sclera from the red lacus lacrimalis • orbicularis oculi muscle = motor innervation by Facial Nerve (VII) to close the eyelids • levator palpebrae superioris = motor innervation by Oculomotor Nerve (III) to open the eyelids ♦ blood supply = arteries that accompany the sensory nerves ♦ sensory nerve supply = from branches of Ophthalmic V1… - Supraorbital - Supratrochlear - Infratrochelar - Lacrimal

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EYELIDS / PALPEBRAE

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

(from lecture) - functions to protect the eyeball & cornea via the conjunctival reflex - functions to spread lacrimal fluid every time you blink - externally covered by skin - internally covered by mucous conjunctiva • eye lashes / cilia = protects eyes from debris • sebaceous glands • orbicularis oculi muscle = closes the eyelids • tarsal plates • tarsal glands - the white striations seen on the conjunctiva - produces hydrophobic lipid - prevent eyes from sticking to e/o - prevent tears from leaking out • superior & inferior conjunctival fornix ----------------------------------------------------------------------------------• tarsal plates - skeleton of the upper & lower lids - provides strength • orbital septum = limits infection into & out of the orbit • lacrimal sac behind the medial palpebral ligament • medial palpebral ligament - attaches tarsal plate to bone - attachment point for orbicularis oculi muscle • lateral palpebral ligament - attaches tarsal plate to bone - no muscles attach here

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THREE CONCENTRIC COATS OF THE EYEBALL

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

(1) Fibrous Coat • Sclera - this is the white part of the eyeball - covers posterior 5/6 of the eyeball - continuous w/ the Optic Nerve’s outer sheath composed of all 3 meninges continuous w/ the brain therefore, increased CSF pressure  bulging of the eyeball - provides attachment for extraocular muscles - pierced by BV-N’s that came from the Choroid layer • Cornea - this is the transparent covering over the iris & pupil - covers anterior 1/6 of the eyeball - sticks out as a small lump b/c it’s more convex than the sclera - allows light to pass thru the pupil to enter the eyeball - provides the primary refractive focusing of light - contains no BV’s… gets nutrients directly from peripheral BV’s and oxygen directly from the air • Corneoscleral Junction = where the sclera overlaps the cornea (2) Vascular Coat - immediately deep to the fibrous coat • Choroid - thin highly-vascular membrane located b/t the sclera & retina - covers posterior 2/3 of the eyeball - firmly attached to retina - loosely attached to sclera • Ciliary Body - continuous w/ the Choroid layer - located b/t the Choroid & Iris, forming a ring around the eyeball - surrounds & suspends the lens around its entire periphery via the Suspensory Ligament ○ Ciliary Muscles - parasympathetic innervation from Oculomotor Nerve (III)  synapses at Ciliary Ganglion - attached to the lens’ zonular fibers / ligaments - contraction  suspensory ligament loosens for accommodation of the lens for near-focusing ○ Ciliary Processes - secretes aqueous humor for nourishment to the avascular lens & cornea - fluid is reabsorbed thru Schlemm’s Canal • Iris - this is the colored art of your eye w/ the pupil in the center to allow light to enter the eye ○ Constrictor Pupillae Muscle = circular fibers contract to decrease pupil size upon parasympathetic stim ○ Dilator Pupillae Muscle = radial fibers contract to increase pupil size upon sympathetic stimulation (3) Retina - this is the inner lining of the eyeball • outer pigmented layer = stops the light from coming thru the retina • inner neural layer = has photoreceptors that are sensitive to light ○ optic portion - rods = 130 million to function in dim light - cones = 7 million to function in color vision & visual acuity • Macula Lutea = the area in the center that has the most acute vision (more cones, less rods) ○ non-optic portion - ciliary portion = lines the inner aspect of the ciliary body - iridial portion = lines the inner aspect of the iris • Optic Disc = where the Optic Nerve leaves the retina  “blind spot” = no photoreceptors ○ Ora Serrata = the junction b/t the optic & non-optic portions

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Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

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EYEBALL COMPARTMENT

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

• Anterior Chamber - posterior to the cornea - anterior to the iris • Posterior Chamber - posterior to the iris - anterior to the lens - pupil connects the anterior & posterior chambers • Postrenal (Vitreous) Chamber - filled w/ Vitreous Humor - transmits light - holds retina in place - supports the lens

REFRACTIVE MEDIA OF THE EYEBALL (1) Aqueous Humor - clear fluid that fills the anterior & posterior chambers - supplies nutrients to the avascular cornea & lens - secreted by the Ciliary Processes into the posterior chamber - drains into Schlemm’s Canal (2) Vitreous Humor - light-refractive, transparent gel that fills the space that is posterior to the lens and encapsulated by the retina - unlike the Aqueous Humor, this fluid cannot be replaced! (3) Lens - separates the aqueous & vitreous humors - composed of laminated clear fibers than can change refractive ability (4) Cornea

LENS ACCOMODATION ○ Focusing on far objects - suspensory ligaments tighten  lens is tightly pulled flat  focal length is increased for distant vision ○ Focusing on near objects - Oculomotor Nerve (III) controls the 3 events of the accommodation reflex… • extraocular muscles adduct the eyeballs medially • circular pupillae muscles constrict the pupil • ciliary muscles contract  suspensory ligaments loosen  lens relaxes  near focusing

PUPILLARY LIGHT REFLEX • direct pupillary reflex = when the pupil dilates in response to light shone directly into it • consensual papillary reflex = when the left eye dilates in response to the light shone on the right eye

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NERVE SUPPLY

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

• Optic Nerve (II) = transmits special sensory stimuli received from the retina’s photoreceptor cells back to the visual cortex for sight • Ophthalmic Nerve (V1) = general touch sensation to the eyeball is supplied by Short & Long Ciliary Nerves • Sympathetic innervation = post-synaptic fibers from the Superior Cervical Ganglion supplies the Dilator Pupillae muscle

• Parasympathetic innervation = Oculomotor (III) synapses in the Ciliary Ganglion supplies the Constrictor Pupillae & Ciliary muscles BLOOD SUPPLY & DRAINAGE • Anterior Ciliary Arteries  Lacrimal Branch  Ophthalmic Artery • Posterior Ciliary Arteries  Ophthalmic Artery • Central Artery of the Retina  Ophthalmic Artery - it is the only arterial supply to the retina - travels in the center of the Optic Nerve, then enters the Optic Disc to supply the retina - no anastomoses means blockage will result in blindness • 4 Choroid Veins  Superior & Inferior Ophthalmic Veins

LACRIMAL GLAND - a serous gland located behind the superior lateral orbital margin, deep to the conjunctival sac - wraps around the Levator Palpebrae Superioris muscle - 10 – 12 tiny ductules open directly into the superior conjunctival sac • Deep Orbital Lobe • Superficial Palpebral Lobe • pre-ganglionic parasympathetic secretory fibers: originate from the Superior Salivatory Nucleus in the Pons and travel w/ Facial Nerve (VII) Facial Nerve (VII)  Greater Petrosal Nerve  Pterygoid Canal  synapses in Pterygopalatine Ganglion • post-ganglionic parasympathetic fibers: follows along with Zygomaticotemporal Nerve of Maxillary V2 enters the orbit thru the Inferior Orbital Fissure  hitchhikes w/ the Lacrimal Nerve of Ophthalmic V1 NASOLACRIMAL SYSTEM - functions to remove excess tears: - lacrimal lake  punctum openings  lacrimal canaliculi  lacrimal sac  nasolacrimal duct  nasal cavity • Punctums = tiny openings located on top of the upper & lower papillae to soak up excess tears • Superior & Inferior Lacrimal Canaliculi = tiny tubes that deliver the tears to medially to the lacrimal sac • Lacrimal Sac = occupies the upper portion of the bony nasolacrimal canal • Nasolacrimal Duct = a membranous tube that drains the inferior aspect of the lacrimal sac opens below the Inferior Nasal Concha into the Inferior Meatus of the Nasal Cavity (this is why your nose runs when you cry a lot)

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CLINICAL NOTES

Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

• Sty = obstructed / infected ciliary gland ducts • Chalazia = obstruction of a sebaceous gland, resulting in a cyst within the gland • Conjunctivitis = common, contagious inflammation / infection of the conjunctiva • Conjunctival hemorrhages = bright red patches (self-healing brusies) resulting from a punch to the eye / blowing the nose • Cataracts = lens becomes opaque  admits less light to retina  decreased vision • Glaucoma = obstructed drainage of aqueous humor  increased ocular pressure  permanent damage to Optic Nerve (II) & BV’s • Myopia

- near-sightedness - caused by elongation in the eyeball’s long axis - the focused image of distant objects doesn’t quite reach the retina

• Hyperopia

- far-sightedness - caused by shortening of the eyeball’s long axis - the focused image of near objects goes pass beyond the retina

• Astigmatism = caused by an uneven curvature of the lens or cornea  light rays focus on different points on the retina • Dacryostenosis = caused by narrowing of the nasolacrimal duct  persistent tearing • Dacryocystitis = infection of the lacrimal sac

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Ann Nguyen -- NYUCD 2008 D1 Anatomy Notes -- Spring '05

VISUAL PATHWAYS Information from the lateral TEMPORAL fields goes to the NASAL half of both retinas Information from the medial NASAL fields goes to the TEMPORAL half of both retinas Information from the RIGHT visual field goes the LEFT half of both retinas - nasal part of the right retina - temporal part of the left retina Information from the LEFT visual field goes the RIGHT half of both retinas - nasal part of the left retina - temporal part of the right retina As the fibers cross the Optic Chiasma… - outer temporal fibers continue ipsilaterally (same saide) - inner nasal fibers cross contralaterally (opposite side) Information from the RIGHT visual field ends up on the LEFT optic tract Information from the LEFT visual field ends up on the RIGHT optic tract INJURIES TO VARIOUS POINTS IN THE PATHWAY Cutting the OPTIC NERVE  total blindness in both TEMPORAL + NASAL fields of the IPSILATERAL EYE Cutting the OPTIC CHIASM  blindness in the TEMPORAL fields of BOTH EYES  loss of peripheral vision = “tunnel vision” Cutting the RIGHT OPTIC TRACT  blindness in the LEFT FIELD of BOTH EYES Cutting the LEFT OPTIC TRACT  blindness in the RIGHT FIELD of BOTH EYES

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