Orbit

Question 1

What is the function of the lacrimal gland and nasolacrimal duct?

Answer 1

• Lacrimal gland- sits superolaterally on eye and has openings to secrete TEARS into conjunctival sac.
• Nasolacrimal duct- tears run from lacrimal gland medially to lacrimal puncta, to lacrimal sinus, to nasolacrimal duct, to nasal cavity through inferior meatus

Question 2

What is function and innervation of superior tarsal muscle?

Answer 2

Superior tarsal muscle is an involuntary muscle that gives tone to the eyelid. Helps keep eyelid up once levator palpebrae superious has lifted it.
-Innervated by sympathetics, post-ganglionic sympathetics from cervical plexus

Question 3

What is Horner’s syndrome? What causes it and how does it present?

Answer 3

Horner’s syndrome results from a lesion in the superior cervical plexus, this affects the post ganglion sympathetics that innervated superior tarsal m., resulting in drooping eyelid or partial ptosis, miosis (constriction of eye), and anhydrosis (no sweating)

Question 4

What is the function of the tarsal gland?

Answer 4

The tarsal glands secrete and oily/fatty substance that keeps the eyelids from sticking together and tears from penetrating eye.

Question 5

What is the common tendinous ring?

Answer 5

A fibrous ring that is attached to the orbital bone around the optic canal, gives rise to the 4 rectus muscles,

Question 6

What structures run in common tendinous ring?

Answer 6

• optic nerve, inferior & superior divisions of oculomotor nerve, nasociliary nerve, abducent nerve, & ophthalmic artery
o oblique muscles DO NOT take origin from common tendinous ring
o “Structures that do not pass through the common tendinous ring are LeFT Out
♣ Lacrimal nerve
♣ Frontal nerve
♣ Trochlear nerve
♣ Ophthalmic vein

Question 7

What is a sty?

Answer 7

Sty- clogged up ciliary glands
• external hordeolum painful red suppurative (puss-producing) swelling caused by an acute bacterial infection of an eyelash follicle/ obstruction of the ducts of the ciliary glands

Question 8

List the innervation of all of the extra ocular muscles

Answer 8

IO, IR, MR- inferior division occulomotor
SR, (levator palpebra superioris)- superior division CN III
LR- CN VI
SO- CN IV

Question 9

How would you test each muscle for integrity?

Answer 9

You must have visual axis in line of pull for each muscle to test the cranial nerve that innervates the muscle. H Test:
• Superior Rectus Muscle: see if the patient can elevate the eye when in the ABducted position
o in the ABducted position, the superior rectus is the only muscle that can ELEVATE the eye
• Inferior Rectus Muscle: see if the patient can depress the eye when in the ABducted position
o in the ABducted position, the inferior rectus is the only muscle that can DEPRESS the eye
• Medial Rectus Muscle: see if the patient can ADduct the eye
• Lateral Rectus Muscle: see if the patient can ABduct the eye
• Superior Oblique Muscle: see if the patient can depress the eye when in the ADducted position
o in the ADducted position, the superior oblique is the only muscle that can DEPRESS the eye
• Inferior Oblique Muscle: see if the patient can elevate the eye when in the ADducted position
o in the ADducted position, the inferior oblique is the only muscle that can ELEVATE the eye

Question 10

How would a lesion of CN VI present?

Answer 10

Lesion of abducens would cut of LR from contracting. Trouble abducting. Would cause the unopposed medial rectus to ADduct the eye towards the nose

Question 11

How would CN IV lesion present?

Answer 11

Lesion of trochlear nerve would prevent SO contracting.

• will present with a head tilt toward the OPPOSITE SHOULDER to compensate for unopposed extorsion of the inferior oblique in primary gaze
o patient will be unable to DEPRESS the eye in the ADducted position

Question 12

Name the three layers of the eyeball

Answer 12

• FIBROUS TUNIC- anterior 1/6 Cornea (transparent dome) & posterior 5/6 Sclera (white of the eyes)
• VASCULAR TUNIC- middle laye
o Iris= colored portion around pupil, anterior to lens
o Ciliary Body= connects the choroid with the circumference of the iris; ciliaris- smooth muscle involved in accommodation & focusing the lens + ciliary processes that secrete aqueous humor to pressurize eye)
o Choroid= layer adherent to retina, dark reddish brown membrane between sclera & retina; largest portion of vascular tunic; lines most of the sclera
• NEURAL TUNIC Retina (photoreceptors + interneurons + retinal ganglion cells + Macula Lutea + Fovea Capitis)

Question 13

Which layer of the eye contains the photoreceptor cells?

Answer 13

• Photoreceptor cells are located in the NEURAL TUNIC

Question 14

How would a lesion of CN III present?

Answer 14

• Lesion of CN III/ Oculomotor Nerve= will present as an eye that is DOWN & OUT with a DILATED PUPIL (unopposed action of superior oblique & lateral rectus- innervated by trochlear & abducens nerves; PARAsympathetics traveling with CN III are compressed therefore the sphincter pupillae is nonfunctional)

Question 15

What is extorsion/intorsion? Which muscle(s) are responsible for extorsion/intorsion? What is the function of these movements?

Answer 15

• EXTORSION= movement of 12 o’clock position of the eye towards the ear to accommodate for changes in head tilt to keep the retina centered
o MUSCLES inferior rectus muscle; inferior oblique muscle
• INTORSION= movement of 12 o’clock position of the eye towards the nose to accommodate for changes in head tilt to keep the retina centered
o MUSCLES superior rectus muscle; superior oblique muscle

Question 16

What is the optic disc?

Answer 16

• OPTIC DISC= the axons of the retinal ganglion cells come together to form the OPTIC DISC & leave the eye as the optic nerve
o distinct circular area where the sensory fibers & vessels conveyed by the optic nerve enter the eyeball
o contains no photoreceptorsINSENSITIVE TO LIGHT; aka the “blind spot”

Question 17

What is the macula lutea?

Answer 17

• MACULA LUTEA= small area of the retina with special photoreceptor CONES; specialized for VISUAL ACUITY, lateral to optic disc
o used for DAY VISION (color vision & fine detail)
o central portion= FOVEA CAPITIS- highest density of photoreceptors (cones only) for detailed vision

Question 18

What is the function and innervation of ciliaris?

Answer 18

Parasympathetic innervation, is a sphincter around the lens that rounds up to close when contracted, relaxed= round out, for long distance

Question 19

What controls purple dilation and contraction?

Answer 19

Pupil contraction- parasympathetic, sphincter pupillae, narrows iris to bring light in

Pupil dilation- sympathetic- dilator pupillae- widen or dilate during fight or flight

Question 20

Why would you stay away from the fovea centralis when using a laser to reattach the retina?

Answer 20

• the fovea capitis is the area of greatest visual acuity so you would want to be sure to preserve it during laser procedures of the retina

Question 21

What are the ciliary processes and their significance to vision?

Answer 21

• CILIARY PROCESSES= secrete aqueous humor that pressurizes the eye
o aqueous humor provides nutrients for the avascular cornea & lens

Question 22

Where does aqueous humor occupy? Describe movement

Answer 22

Aqueous humor is a clear watery fluid in anterior and posterior chambers of the eyeball. It is made by ciliary processes in the posterior chamber and moves anteriorly through pupil. They drain through filtration angles into venous canals (of Schlemm)

Question 23

What is glaucoma? What is the anatomical basis for this disorder?

Answer 23

• GLAUCOMA increased intraocular pressure caused by an increase in aqueous humor production or a decrease in drainage of aqueous humor through the scleral venous sinus into blood circulation
o blindness can result from compression of the inner layer of the retina & retinal arteries

Question 24

Describe the lens and vitreous body

Answer 24

• The lens is a transparent bioconvex structure, surrounded by ciliary process which give rise to suspensory ligaments of lens
• The vitreous body is posterior to the lens and the main inner part of the eyeball. Filled with gel and collagen fibers.

Question 25

What is main blood supply to the orbit?

Answer 25

Opthalamic artery, arise from ICA, runs lateral to medial

Question 26

Describe venous return from the orbit

Answer 26

The superior (from supraorbital) and inferior (from angular) ophthalmic veins originate in the anterior aspect of the orbit, meet and exit via the SOF, enters the cavernous sinus

Question 27

What is a great place for infection to spread in the orbit? What is the consequences?

Answer 27

Cavernous sinous, getting blood from the face and eyes, drains into this moist dark place.

Infection could spread, could push on abducens nerve (can’t abduct eye), then if push on V 1 2 3 lose movement of eye

Question 28

What are the 3 major branches of V1 in the orbit? What is/are the major modalities of all 3 of these branches?

Answer 28

• NASOCILIARY NERVE passes over optic nerve (from lateral to medial); provides roots to ciliary ganglion & gives off long ciliary nerves to back of eyeball
o SENSORY- GSA (general somatic afferent)
o Roots of Ciliary Ganglion suspend ciliary ganglion; continue as short ciliary nerves
o LONG CILIARY NERVES (2) pass directly into back of eyeball; innervate anterior sclera, cornea, iris dilator, bulbar conjunctiva (postganglionic sympathetic fibers hitch a ride)
o SHORT CILIARY NERVES (10-20) leave the ciliary ganglion & penetrate the eye; innervate posterior sclera, ciliary muscles, & iris sphincter (postganglionic parasympathetic fibers hitch a ride)
o ETHMOIDAL NERVES (ANTERIOR & POSTERIOR) pass into ethmoidal air cells through respective ethmoidal foramina
• FRONTAL NERVE runs superior to levator palpebrae superioris muscle; divides into SUPRAORBITAL & SUPRATROCHLEAR NERVES (supply forehead & anterior scalp)
o SENSORY- GSA (general somatic afferent)
• LACRIMAL NERVE innervates lacrimal gland; then becomes cutaneous & innervates lateral canthus
o SENSORY- GSA (general somatic afferent)

Question 29

Describe the 3 branches of V1 in orbit

Answer 29

NFL
Nasociliary- most medial, 3 branches, ethymoidal- painful if ethmoid air cells infected
Long ciliary- sensory info from eye, pain, sym ride along
Short ciliary- travel through the ciliary ganglion without synapsing, back of eye is target, has para and sym with sensory

Frontal- all sensory- 2 branches, supratrochlear (more medial) and suprorbital

Lacrimal- sensory to lateral orbit, para to lacrimal ride on lacrimal nerve

Question 30

Where does the autonomic innervation for the orbit come from (symp/parasymp)?

Answer 30

• PARASYMPATHETIC INNERVATION (GVE-pupillary constriction & accommodation)
o PREganglionic Fibers= CN III
♣ originate in Edinger Westphal Nucleus (midbrain); carried by inferior division of OCULOMOTOR NERVE as its GVE component
♣ synapse in the CILIARY GANGLION (suspended from nasociliary nerve via its sensory roots; located on lateral side of optic nerve)
o POSTganglionic Fibers= travel along SHORT CILIARY NERVES (branches of nasociliary nerve from CN V1-trigeminal nerve ophthalmic divison)
• SYMPATHETIC INNERVATION (GVE-pupillary dilation & tonic innervation of superior tarsal muscle)
o PREganglionic Fibers= originate in lower cervical & upper thoracic spinal cord (C8-T2); ride on sympathetic trunk all the way up to the SUPERIOR CERVICAL GANGLION & synapse
o POSTganglionic Fibers= follow & cling around internal carotid artery to from plexus; jump off ophthalmic plexus within orbit; pass ciliary ganglion without synapsing then take SHORT CILIARY NERVES or LONG CILIARY NERVES to the eyeball
♣ Long Ciliary Nerves innervate dilator pupillae (radially oriented)
♣ other fibers are carried to the superior tarsal muscle by hitching a ride on the superior division of CN III (Oculomotor Nerve)

Question 31

What types of fibers do the long & short ciliary nerves carry?

Answer 31

• Long Ciliary Nerves= POSTganglionic SYMPATHETIC FIBERS

* Short Ciliary Nerves= POSTganglionic PARAsympathetic fibers & some sympathetic fibers

Question 32

What controls pupil dilation? Contraction?

Answer 32

• Pupil DILATION= SYMPATHETIC

* Pupil CONTRACTION= PARASYMPATHETIC

Question 33

How does the lacrimal gland get its vasomotor (secretory) innervation? Where do the sympathetic fibers come from? The parasympathetic fibers?

Answer 33

• LACRIMAL NERVE (CN V1) provides sensory innervation to the lacrimal gland
• PARASYMPATHETIC= SECRETOMOTOR
o PREganglionic PARAsympathetic fibers are conveyed from FACIAL NERVE (CN VII) by the GREATER PETROSAL NERVE to NERVE OF PTERYGOID CANAL to synapse in pterygopalatine ganglion
o POSTganglionic PARAsympathetic fibers then hitch a ride on CN V2 (Maxillary Nerve) ZYGOMATIC NERVE (branch of CN V2) ZYGOMATICOTEMPORAL NERVE (CN V2) LACRIMAL NERVE (CN V1)target
• SYMPATHETIC= VASOCONSTRICTION
o POSTganglionic sympathetic fibers from SCG form the internal carotid plexus leave ICA plexus as the DEEP PETROSAL NERVEjoin preganglionic parasympathetic fibers to form NERVE OF THE PTERYGOID CANALpass through pterygopalatine ganglion without synapsing hitch a ride on the same path as postganglionic parasympathetic fibers to reach their targets in lacrimal gland

Question 34

Which vessel supplies all the structures of the orbit? Describe the origin & course of this artery. Through what opening does this vessel access the orbit? Which vessel supplies the retina?

Answer 34

• OPHTHALMIC ARTERY: supplies all structures of the orbit; branches off the ICA & enters orbit through OPTIC CANAL with the OPTIC NERVE (CN II) crosses over optic nerve from lateral to medial & continues anteriorly in the orbit giving off several branches:
o Central Retinal Artery= enters optic nerve while in optic canal & supplies retina (small but critically important)
o Lacrimal Artery= passes anteriorly in the orbit & sits on top of the lateral rectus; supplies lacrimal gland & becomes cutaneous
o Supraorbital Artery= passes anteriorly through the supraorbital foramen/notch
o Supratrochlear= small branch medial to the supraorbital artery
o Ethmoidal Arteries (Anterior & Posterior)= pass medially into ethmoidal air cells via ethmoidal foramina
o Dorsal Nasal Artery= terminal branch of ophthalmic artery; anastomoses with angular artery

Question 35

Name 2 nerves/vessels that exit the orbit to supply the forehead & anterior scalp

Answer 35

• Supraorbital & Supratrochlear Nerves & Arteries pass through supraorbital foramen

Question 36

• Roof of Orbit:

Answer 36

o FRONTAL BONE Supraorbital Notch/Foramen
o LESSER WING OF SPHENOID BONE S. Optic Foramen (Optic Nerve/ CN II & Ophthalmic Artery)
o Fovea Trochlearis (medial to supraorbital notch)

Question 37

• Lateral Wall of Orbit: strongest wall

Answer 37

o ZYGOMATIC BONE (anteriorly) Lateral Orbital Tubercle
o GREATER WING OF SPHENOID BONE (posteriorly)
o separated from roof posteriorly by superior orbital fissure

Question 38

• Floor of Orbit:

Answer 38

o Orbital plate of MAXILLARY BONE
o Orbital process of PALATINE BONE
o Infraorbital Margin
o Infraorbital Foramen

Question 39

• Medial Wall of Orbit:

Answer 39

o Lamina Papyracea of ETHMOID BONE
o LACRIMAL BONE
o Body of ETHMOID BONE
o ANTERIOR & POSTERIOR ETHMOIDAL FORAMINA (Artery & Nerve; in FRONTAL BONE)

Question 40

• Posterior Orbit:

Answer 40

o Optic Foramen= yellow arrow
o Superior Orbital Fissure= green arrow
♣ branches of CN V1, nerves to eye muscles, superior ophthalmic vein)
o Inferior Orbital Fissure= blue arrow
♣ infraorbital artery & vein, infraorbital & zygomatic branches of maxillary nerve (CN V2), & inferior ophthalmic vein

Question 41

What is a blow out fracture & how does it present clinically?

Answer 41

• A sharp blow to the lower orbital margin can induce a BLOW OUT FRACTURE whereby the orbital floor fractures & momentarily gives way, entrapping the inferior rectus muscle
o patient will be unable to elevate eye on affected side & may also experience hypoesthesia of the lower eyelid & cheek (infraorbital nerve)
Drains into maxillary sinus

Question 42

What is exophthalmos? What can cause this?

Answer 42

• EXOPHTHALMOS bulging eyeball
o congestion of orbital venous system from a carotid-cavernous fistula
o growths- benign or malignant
o Grave’s Disease- excess fat deposits

Question 43

What is ptosis? What can result in this condition?

Answer 43

• PTOSIS= droopy upper eyelid
o can be caused by a lesion of the oculomotor nerve (CN III) or by damage to the sympathetic superior cervical ganglion (Horner’s Syndrome)

Question 44

What is the pupillary light reflex? What cranial nerves does it involve?

Answer 44

• PUPILLARY LIGHT REFLEX= flashing light test will cause bilateral pupillary constriction
o CN II is the AFFERENT pathway; CN III is the EFFERENT pathway
♣ pupillary fibers exit CN II & make bilateral synapses in midbrain structures associated with CN IIIcause bilateral constriction of pupils

Question 45

What is the corneal reflex? What cranial nerves does it involve?

Answer 45

• CORNEAL REFLEX= touching the cornea (innervated by CN V1- ophthalmic division of trigeminal nerve) causes lacrimation (CN VII), pupillary constriction (CN III), & a protective blink (CN VII)
o CN V1 is AFFERENT pathway; CN III is EFFERENT pathway