Extraocular Muscles & Tenon's Capsule 1

Which cranial nerve innervates the superior oblique?

CN IV (trochlear)

Which cranial nerve innervates the lateral rectus?

CN VI (abducens)

If you suspect that the right lateral rectus has a problem, and you ARE able to move the right eye medially, what is the likely cause?

CN VI palsy

Where does the inferior rectus originate?

CTR

Where does the superior rectus originate?

CTR and dural sheath of optic nerve

Where does the medial rectus originate? Along which wall of the orbit does it pass?

CTR and dural sheath of optic nerve, medial

Where does the lateral rectus originate? Along which wall of the orbit does it pass?

CTR, lateral

Which of the following EOMs inserts closest to the limbus? A. superior oblique B. inferior rectus C. inferior oblique D. medial rectus E. superior rectus F. lateral rectus

D (medial rectus is very important for convergence, so it inserts closest)

What are the FIVE main things that pierce Tenon's capsule?

EOM tendons, LPCN/LPCA, SPCN/SPCA, vortex veins, optic nerve

What is/are the agonist(s) for straight depression? Antagonist(s)?

IR and SO are agonists, SR and IO are antagonists

What is the agonist for straight adduction? Antagonist?

MR is agonist, LR is antagonist

Which 3 muscles would be synergists for adduction of the left eye?

MR, IR, SR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RIO, LSR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RIR, LSO

After the SO passes through the trochlear pulley (its functional origin), it turns poterolaterally and pierces what, then passing under the SR muscle tendon and spreading out in a fan-like manner to insert into the sclera?

Tenon's capsule

When the eye is looking straight ahead in primary gaze, the inferior rectus muscle passes anterolaterally along the orbital floor at what angle to the globe's anterior-posterior axis?

23

When the eye is looking straight ahead in primary gaze, the superior rectus muscle passes anterolaterally at what angle to the globe's anterior-posterior axis?

23

When the eye is looking straight ahead in primary gaze, the inferior oblique tendon forms what angle with the globe's anterior-posterior axis?

51

When the eye is looking straight ahead in primary gaze, the superior oblique tendon forms what angle with the globe's anterior-posterior axis so that the eye is pulled from the functional origin? (its pulley)

54

What is the significance of the extension between the inferior rectus fascia and suspensory ligament of Lockwood? (Hint: it attaches to the inferior tarsal plate)

as eyeball is depressed, lower eyelid is raised too

What is the significance of the expansion that extends between the LPS and SR?

as eyeball is elevated, upper eyelid is raised too

refers to a strabismus in which one of the eyes (or both) is turned AWAY from the nose

exotropia

12 o'clock position of the eye rotates laterally (towards the ear)

extorsion

What happens along the SAGITTAL axis when the IO contracts?

extorsion

What happens along the SAGITTAL axis when the IR contracts?

extorsion

Do the inferior rectus and oblique cause intorsion or extorsion?

extorsion ("inferior" people do "extortion")

What does the inferior oblique do to the eye?

extorsion, elevation, abduction

The small depression on the orbital plate of the maxilla from which the inferior oblique originates lies just lateral to what?

nasolacrimal canal

What may cause the inability to move an extraocular muscle? (3 reasons)

nerve damage, restriction of muscle, restriction of antagonist

inflammatory response directed against the optic nerve's myelin, which leads to demyelination & axon loss, leading to ganglion cell death and decreased visual acuity ALSO affects the meninges that surrounds the optic nerve, so it can cause pain with eye movement, caused by the pulling of the SR and MR on the optic nerve's inflamed dural covering as the affected eyeball moves

optic neuritis

Where does the superior oblique insert into the sclera in relation to the equator and vertical axis?

posterior

Where does the inferior oblique insert into the sclera in relation to the equator and vertical axis?

posterior (just like the SO)

Where do the oblique muscles insert on the eyeball?

posterior portion (posterior to equator, posterior to vertical axis)

After originating from the lesser wing of the sphenoid bone, the superior oblique passes forward between which two walls the orbit on the way to the trochlea?

roof, medial

hammock-like dense CT sheet that extends from the zygomatic bone to the lacrimal bone formed by contributions from Tenon's capsule and the muscle fascias of the inferior rectus and inferior oblique supports the eyeball and maintains its position in the orbit, and acts like a "sling" to prevent the eyeball from falling into the maxillary sinus if the orbital floor is damaged

suspensory ligament (of Lockwood)

What do the fascia of the inferior rectus and inferior oblique form?

suspensory ligament of Lockwood

When we look up, what two synergists are acting to make this happen?

superior rectus, inferior oblique

refers to two or more muscles that move ONE eye in the same direction

synergists

A symptom of optic neuritis may be pain with eye movement caused by the pulling of what two EOMs on the optic nerve's inflamed dura mater?

superior rectus, medial rectus

Each rectus muscle originates from the common tendinous ring. HOWEVER, which two EOMs also originate from the dural sheath surrounding the optic nerve?

superior rectus, medial rectus

Into what quadrant of the eyeball does the superior oblique insert?

upper posterolateral

refers to simultaneous movement of BOTH eyes in the SAME direction to keep the two eyes fixed on an object

version

Fick's axis that allows abduction & adduction

vertical

dense sheet of connective tissue that surrounds the eyeball from near the corneoscleral junction to the optic nerve and separates the eyeball from the orbital fat **like a glove or a sock pulled over the eyeball: forms a socket for the eyeball to sit in!

Tenon's capsule

What forms the suspensory ligament of Lockwood?

Tenon's capsule and muscle fascias of IR and IO

potential space between the episclera of the eyeball and the capsule; potential space in which fluids can accumulate

Tenon's space (episcleral space)

The muscle fascia between which 2 of the following muscles allows coordinated movement of the eyelid and eyeball when looking up? A. SR B. LPS C. IR D. IO E. SO

A, B

Which 2 of the following EOMs inserts on the posterior portion of the globe? A. superior oblique B. inferior rectus C. inferior oblique D. medial rectus E. superior rectus F. lateral rectus

A, C

Which of the following muscles would be located superior to the superior rectus if a cut were made BEHIND the eyeball? A. inferior rectus B. levator palpebrae superioris C. superior oblique D. superior rectus E. inferior oblique

B (cutting behind the eyeball = SO runs along the wall, IO isn't there since it doesn't originate from the apex)

Which 3 of the following structures pierce Tenon's posterior to the equator? A. lateral rectus B. inferior oblique C. short posterior ciliary arteries D. medial rectus E. inferior rectus F. vortex veins

B, C, F

The check ligament that limits adduction attaches to which of the following orbital structures/locations? A. zygomatic orbital margin B. maxillary orbital margin C. lateral orbital tubercle D. anterior lacrimal crest

C

principle stating that both muscles moving the eyes into a particular direction will simultaneously receive equal innervation from the CNS example: RLR and LMR get the same innervation when the patient is looking straight right

Hering's law

Even though the other EOMs besides the MR and LR don't have well developed fascia "expansions", a thinner expansion extends between the fascia of what two muscles?

LPS, superior rectus

What is the agonist for straight abduction? Antagonist?

LR is agonist, MR is antagonist

Which 3 muscles would be synergists for abduction of the left eye?

LR, SO, IO

How do you remember which cranial nerves innervate which EOMs?

LR6, SO4, all others are 3

Consider the image. Which EOM is not functioning properly?

LSR

If a patient is asked to look to the right, and the right eye cannot move laterally, one possible cause may be restriction of the ____ muscle due to fibrosis or fluid accumulating by the muscle or entrapment of the muscle as may result from a lateral orbital wall fracture.

RLR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RLR, LMR

If a patient is asked to look to the right, and the right eye cannot move laterally, one possible cause may be paralysis of the ____ muscle due to damage to the ____ nerve.

RLR, abducens

If a patient is asked to look to the right, and the right eye cannot move laterally, one possible cause may be restriction of the antagonistic ____ muscle due to entrapment of the muscle as may result from a medial orbital wall fracture.

RMR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RMR, LLR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RSO, LIR

Which two muscles are yoked when the patient is looking down and to the left?

RSO, LIR

Consider the image. Which EOM is not functioning properly?

RSR

If the patient is looking in the gaze shown in the image, what are the two yoked muscles being tested here?

RSR, LIO

How can we remember the relative attachment distances of the four rectus muscles to the eyeball, starting with the one FARTHEST away from the limbus?

SLIM (superior, lateral, inferior, medial)

What is/are the agonist(s) for straight elevation? Antagonist(s)?

SR and IO are agonists, IR and SO are antagonists

principle stating that increased innervation to an agonist muscle is accompanied by simultaneous proportional decrease in innervation (aka relaxation) to the antagonist muscle

Sherrington's law

Does the medial check ligament limit abduction or adduction?

abduction

What does the lateral rectus do to the eye?

abduction

What happens along the VERTICAL axis when the IO contracts?

abduction

What happens along the VERTICAL axis when the LR contracts?

abduction

What happens along the VERTICAL axis when the SO contracts?

abduction

rotation of the eye laterally

abduction

Do the superior and inferior oblique cause abduction or adduction?

abduction ("OBlique ABs")

Does the inferior rectus lie above or below the inferior oblique?

above

Does the superior rectus lie above or below the superior oblique's tendon?

above

Do the superior and inferior rectus cause abduction or adduction?

adduction

Does the lateral check ligament limit abduction or adduction?

adduction

What does the medial rectus do to the eye?

adduction

What happens along the VERTICAL axis when the MR contracts?

adduction

What happens along the VERTICAL axis when the SR contracts?

adduction

rotation of the eye medially

adduction

What happens along the VERTICAL axis when the IR contracts?

adduction (just like SR)

muscle that moves ONE eye in a given direction (contracts) vs. muscle in the SAME eye that moves it in the opposite direction (relaxes)

agonist vs. antagonist

What is a forced duction test that can be performed to help determine if muscle restriction of the reason that am muscle is not moving during EOM testing?

attempt to move the eyeball with a Q tip placed on the bulbar conjunctiva in the opposite direction from suspected restriction

Functions of Tenon's capsule: 1. acts as a ____ to prevent the spread of orbital infections into the globe 2. ____ and supports the eyeball in the orbit 3. permits ____ movement of the EOMs to move the eyeball

barrier, positions, smooth

Anteriorly, is Tenon's capsule firmly attached in front of, at, or behind the limbus?

behind

Does the superior rectus muscle lie above or below the levator palpebrae superioris?

below

When passing along the medial wall of the orbit, where is the medial rectus in relation to the superior oblique?

below its belly

Where is Tenon's capsule?

between bulbar conjunctiva and sclera (BC is external)

Does the medial rectus insert closest or farthest from the limbus?

closest

two terms for oval connective tissue ring made of thickened periorbita located at the apex of the orbit; surrounds the optic canal and the central portion of the superior orbital fissure

common tendinous ring

Where do ALL of the rectus muscles originate?

common tendinous ring (annulus of Zinn)

What does the superior oblique do to the eyeball: elevate or depress?

depress

Do the inferior rectus and superior oblique cause elevation or depression?

depression

What happens along the HORIZONTAL axis when the IR contracts?

depression

What happens along the HORIZONTAL axis when the SO contracts?

depression

rotation of the eye downward

depression

What does the inferior rectus do to the eye?

depression, extorsion, adduction

If there is a RIGHT third nerve palsy, how will that eye be turned? Why?

down and out, LR and SO are in control

refers to the movement of ONE eyeball; movement that each eye can do alone

duction

Each rectus muscle originates from the common tendinous ring. HOWEVER, the superior rectus and medial rectus also originate from what other location?

dural sheath surrounding optic nerve

What does the inferior oblique do to the eyeball: elevate or depress?

elevate

Do the superior rectus and inferior oblique cause elevation or depression?

elevation

What happens along the HORIZONTAL axis when the IO contracts?

elevation

What happens along the HORIZONTAL axis when the SR contracts?

elevation

rotation of the eye upward

elevation

What does the superior rectus do to the eye?

elevation, intorsion, adduction

refers to removal of the eyeball from Tenon's capsule and the entire orbit as a whole (serves as a socket for prosthetic eye)

enucleation

refers to a strabismus in which one of the eyes (or both) is turned IN towards the nose

esotropia

refers to the removal of the cornea, uveal layer, and retina, leaving the sclera, optic nerve, and EOMs intact; ocular implant placed into scleral shell

evisceration

refers to the removal of all orbital contents so that only the bone remains

exenteration

Does the superior rectus insert closest or farthest from the limbus?

farthest

As the tendons of the extraocular muscles pierce Tenon's capsule to insert into the sclera, Tenon's capsule forms a tubular sleeve that covers the tendons of the extraocular muscles and reflects back onto the muscles to be continuous with the muscles' what?

fascia

other name for Tenon's capsule

fascia bulbi

If you suspect that the right lateral rectus has a problem, and you ARE NOT able to move the right eye medially, what is the likely cause?

fibrosis or entrapment of the RLR

Fick's axis that allows elevation & depression

horizontal (transverse)

Which oblique muscle attaches to the sclera overlying the macula of the retina: superior or inferior?

inferior

Which cranial nerve innervates the inferior oblique?

inferior division of CN III (oculomotor)

Which cranial nerve innervates the inferior rectus?

inferior division of CN III (oculomotor)

Which cranial nerve innervates the medial rectus?

inferior division of CN III (oculomotor)

Which muscle is being tested in the RIGHT eye when the patient looks UP and to the LEFT?

inferior oblique

What is the only EOM that does NOT originate from the orbital apex?

inferior oblique (it originates from the maxilla on the orbital floor)

Even though the other EOMs besides the MR and LR don't have well developed fascia "expansions", the fascia of which two other EOMs blend together to form the suspensory ligament of Lockwood?

inferior rectus, inferior oblique

When we look down, what two synergists are acting to make this happen?

inferior rectus, superior oblique

An anterior extension between what muscles/structures attaches to the inferior edge of the inferior tarsal plate?

inferior rectus, suspensory ligament

An anterior extension between the inferior rectus fascia and suspensory ligament of Lockwood attaches to what structure? **when a person looks down, the lower eyelids moves down too

inferior tarsal plate

12 o'clock position of the eye rotates medially (towards the nose)

intorsion

Do the superior rectus and oblique cause intorsion or extorsion?

intorsion

What happens along the SAGITTAL axis when the SO contracts?

intorsion

What happens along the SAGITTAL axis when the SR contracts?

intorsion

What does the superior oblique do to the eye?

intorsion, depression, abduction

What does the medial check ligament attach to?

lacrimal bone, behind posterior lacrimal crest

The eye can only move inward medially so far. What limits that?

lateral check ligament

What two things attach to the lateral orbital tubercle?

lateral check ligament, ligament of Lockwood, lateral palpebral ligament, LPS

What does the lateral check ligament attach to?

lateral orbital tubercle (on zygomatic bone)

If the patient looks in extreme RIGHT gaze, you test the right ____ muscle and the left ____ muscle as the patient looks ____ with the right eye and ____ with the left eye.

lateral rectus, medial rectus, right, right

Where does the superior oblique originate? (anatomically)

lesser wing of sphenoid

Where is the superior oblique's anatomical origin?

lesser wing of sphenoid (just outside CTR, superior and medial to optic canal)

Into what quadrant of the eyeball doe the inferior oblique insert?

lower posterolateral

The inferior oblique inserts onto the sclera overlying what retinal structure?

macula

What is the inferior oblique's anatomical origin?

maxilla on orbital floor (just posterior to orbital margin and lateral to nasolacrimal canal opening)

Where does the inferior oblique originate?

maxilla on orbital floor (small depression on the orbital plate of the maxilla that lies just posterior to the orbital margin and just lateral to the nasolacrimal canal)

The suspensory ligament of Lockwood can act like a sling or hammock to support the eyeball and prevent it from falling into where if the orbital floor is damaged?

maxillary sinus

Why are the EOMs clinically important?

may be misaligned, indicators of CN function, affected by diseases (strabismus; CN III, IV, & VI; diabetes, thyroid associated ophthalmopathy, Graves disease, myasthenia gravis)

Which EOM attachment to the eyeball is CLOSEST to the limbus? (only 5.5 mm away)

medial

The eye can only move outward laterally so far. What limits that?

medial check ligament

Which EOM is the shortest and therefore the strongest?

medial rectus (bc it has the most mass and most anterior insertion into the sclera, so has greatest leverage)

The muscle fascia of which two EOMs are expanded to form strong "check ligaments"? these limit how far these muscles pull on the eyeball, and thus keep their movements "in check"

medial rectus, lateral rectus

If the patient looks in extreme LEFT gaze, you test the right ____ muscle and the left ____ muscle as the patient looks ____ with the right eye and ____ with the left eye.

medial rectus, lateral rectus, left, left

Fick's axis that allows intorsion & extorsion **axis passes through pupil and the reference point is the 12 o'clock position of the cornea

sagittal

Posteriorly, what two things does Tenon's capsule fuse with?

sclera around exit of optic nerve, dura mater around optic nerve

inward spiral formed when starting at the attachment of the superior rectus to the eyeball and then going to lateral, then medial, then ending with the attachment of the medial rectus to the eyeball

spiral of Tillaux

manifest misalignment of the eyes so that they point in different directions; the eyes are unable to focus simultaneously on a single point could be due to nerve damage OR mechanical restriction of the muscle, whether due to fibrosis or fluid accumulating by the muscle or entrapment of the muscle (from a fracture)

strabismus

Which EOM attachment to the eyeball is FARTHEST to the limbus? (7.7 mm away)

superior

Where is the attachment for the expansion that extends between the LPS and SR?

superior conjunctival fornix

Which cranial nerve innervates the superior rectus?

superior division of CN III (oculomotor)

Why don't we include straight up and straight down in the pattern of the physiologic H?

those gazes involve the action of two EOMs, not just one (SR/IO and IR/SO)

Where is the superior oblique's functional origin?

trochlear pulley

True or false: At any given time, the position of the eyeball is determined by the state of contraction or relaxation of ALL six EOMs.

true (in primary gaze, keeps the eye center and in the palpebral fissure)

True or false: EOMs are constantly active with a low level of tonic innervation.

true (no muscle acts alone!)

If you suspect that the right lateral rectus has a problem, how would you perform the forced duction test?

try to move the right eye medially

Do the tendons of the EOMs pierce Tenon's capsule?

yes (they have to in order to insert into the sclera)

term for muscles in each eye that work at the same time and in the same direction to accomplish a version movement (muscles in DIFFERENT eyes) example: the right lateral rectus and left medial rectus are ____ muscles **this is what the physiologic H shows!!

yoked

Between which two bones of the orbit does the suspensory ligament of Lockwood extend?

zygomatic, lacrimal