ORBIT + EXTRAOCULAR MUSCLES

Question 1

Describe what may bring about Papilledema.

Answer 1

Increased intracranial CSF pressure can compress the optic nerve (CN II) which is an extension of the brain and lead to blurry peripheral vision.

Question 2

What are the 3 steps (each starting with C) for accommodation of the eye, when looking at a nearby object?

Answer 2

Contraction of the ciliary muscles, constriction of the pupil, Convergence of the eyes through the medial rectus muscle.

Question 3

What are the structures found in the common ring tendon? What of those outside CRT?

Answer 3

Inside CRT: CN III, VI and Nasociliary (V1 branch)

Outside: CN IV, Lacrimal Nerve

Question 4

What are the 4 branches of the Nasociliary nerve?

Answer 4

Long ciliary nerve, ethmoidal nerve, Infratrochlear nerve, branch to ciliary muscle.

Question 5

What muscles does the superior division of the occulomotor nerve (CN III) innervate?

Answer 5

Superior Rectus and Levator Palpebrae Superioris (LPS)

Question 6

What does the inferior occulomotor nerve (CN III) innervate?

Answer 6

Pupillary constriction, ciliary muscles, inferior rectus, inferior oblique and medial rectus

Question 7

If someone’s occulomotor nerve is injured, what signs would present?

Answer 7

Eye movement would move inferior and laterally since only the Lateral rectus and Superior Oblique muscles would work. There would also be a “blown” or large pupil because of the decreased parasympathetic innervation.

Question 8

What nerves innervate the Superior oblique and lateral rectus muscles, respectively?

Answer 8

Trochlear nerve (CN IV) innervates the SO and the Abducens nerve (CN VI) innervates the LR.

Question 9

A 23 year old man comes into the office with eye issues. He finds it difficult to move his eyes inferior and laterally. What nerve or muscle was most likely injured?

Answer 9

The trochlear nerve (CN IV) or superior oblique muscle can be injured.

Question 10

What cranial nerve is suspected to be injured if a person’s eye deviates medially, unprompted (Internal Strabismus)?

Answer 10

Abducens nerve (CN VI)

Question 11

Where is the the blind spot located in the eye? What of the fovea?

Answer 11

Optic disk where the optic axons enter the eye to come into the retina;
Center of the macula where the highest concentration of cones is (sharpest vision)

Question 12

Describe the passage of aqueous humor in the eyeball.

Answer 12

Ciliary processes in the eyeball (behind the posterior chamber) secretes aqueous humor that flows into the anterior chamber. Aqueous humor can be resorted into venous channels in the Canal of Schlemm .

Question 13

What disease can occur if the drainage of aqueous humor is interfered inside the eye?

Answer 13

Glaucoma from increased intraocular pressure.

Question 14

What are the Suspensory ligaments responsible for?

Answer 14

They attach to the ciliary bodies and increase tension to stretch the lens when contracted.

Question 15

What causes Presbyopia?

Answer 15

If the lens loses its natural elastic recoil, presbyopia can occur. This involves a person not being able to see nearby objects and occurs naturally with age.

Question 16

Refraction is ______ and ______ at the cornea, but ______ at the lens.

Answer 16

Constant and greater @ cornea;

Modifiable at the lens

Question 17

What are the 2 aspects of the near reflex?

Answer 17

Convergence and Pupillary Constriction

Question 18

When evaluating extraocular muscles of the orbit, the oblique muscles are tested when the eye is _________. Meanwhile, the rectus muscles are tested when the eye is _________.

Answer 18

Adducted;

Abducted

Question 19

What structures pass through each of the two foramen near the orbit?

Answer 19

Supraorbital foramen - Ophthalmic division (V1) and Supraorbital Nerve, artery and vein;
Infraorbital foramen - Maxillary division (V2) and the infraorbital nerve, artery and vein.

Question 20

What 7 structures pass through the superior orbital fissure?

Answer 20

Superior ophthalmic vein = branch of cavernous sinus;
CN III (occulomotor: superior and inferior divisions);
CN IV (trochlear); Lacrimal nerve (V1 superior); Frontal nerve (V1)
Nasociliary nerve (V1); CN VI (abducens)

Question 21

What structures pass through the inferior orbital fissure?

Answer 21

Infraorbital nerve (V2); Zygomatic nerve (V2); Inferior Ophthalmic vein

Question 22

What extraocular muscles are innervated by the superior division of the occulomotor nerve (CN III)? What of the inferior division?

Answer 22

Superior division of CN III = Levator palpebrae superiosis + Superior Rectus;
Inferior division CN III = inferior oblique, inferior rectus + medial rectus

Question 23

What are the 3 nerve branches of the ophthalmic division (V1) of the trigeminal nerve and what do they innervate?

Answer 23

Nasociliary nerve - innervates ethmoid spaces of nasal sinuses
Frontal nerve - splits into supratrochlear and supraorbital nerves
Lacrimal nerve - sensory innervation to lacrimal gland and skin lateral to orbit “NFL”

Question 24

The medial wall of the eye is the translucent, _______ sinus. The ________ sinus is located below the orbit.

Answer 24

Sphenoid sinus;

Maxillary sinus

Question 25

What muscles elevate the eyeball (provide their innervations)?

Answer 25

Superior rectus (CN III superior division) and the Inferior oblique (CN III inferior division)

Question 26

What muscles depress the eyeball (provide their innervations)?

Answer 26

Inferior rectus (CN III inferior division) and Superior oblique (CN IV, trochlear).

Question 27

To get pure elevation of the eyeball what muscles contract? What of pure depression of the eyeball?

Answer 27

Elevation: Superior rectus + inferior oblique
Depression: Inferior rectus + superior oblique

Question 28

I am testing extra-ocular muscles of the right eye with the “H in Space” assessment. If I move a pencil to my right then upwards the muscle I am testing is the…

Answer 28

Right Superior rectus muscle because my eye is already abducted and IO cannot act on this axis.

Question 29

I am testing extra-ocular muscles of the right eye with the “H in Space” assessment. I move my pencil downward and towards my left in order to test my…

Answer 29

Right Superior oblique muscle (because the inferior rectus cannot work on that axis)

Question 30

The structures that pass through the common ring tendon are…

Answer 30

More medial structures of the superior orbital fissure which include: CN III superior division, CN VI and Nasociliary nerve (V1).

Question 31

What are the nerves of the orbit moving from medial to lateral in the 1st layer?

Answer 31

Layer 1 - Trochlear nerve, Frontal nerve, supratrochlear Nerve + supraorbital nerve, Lacrimal Nerve

Question 32

What are the nerves of the orbit in the 2nd layer?

Answer 32

Nasociliary nerve and CN III superior division

Question 33

What are the nerves of the orbit in the 3rd layer?

Answer 33

Optic nerve, ciliary ganglion and Abducens nerve

Question 34

What nerve of the orbit is in the 4th layer?

Answer 34

CN III inferior division

Question 35

What 2 nerves branch off from the Maxillary division (V2) of the trigeminal nerve and what do they innervate?

Answer 35

Zygomatic nerve - innervates skin over zygomatic arch and temporalis bone;
Infraorbital nerve - innervates lower eyelid and upper lip

Question 36

At what artery is the anastomoses between the internal and external carotid arteries around the orbit? What is the normal and abnormal direction of flow across these arterial systems?

Answer 36

They anastomose along the ophthalmic artery above the orbit.
Normal flow is from inside orbit to out towards the external carotid.
Abnormal flow is from outside to in, which occurs if there is an obstruction that leads to reduced intraorbital BP.

Question 37

Explain how popping a pimple on your cheek can lead to an infection of the cavernous sinus.

Answer 37

Popping a pimple can spread infection towards the pterygoid venous plexus which causes backflow towards the inferior ophthalmic vein. This flows back into the superior ophthalmic vein which can head back to the cavernous sinus in the MCF.

Question 38

What cranial nerves carry pre-ganglionic PSNS fibers along with them?

Answer 38

Cranial nerves 3, 7, 9 and 10

Question 39

How do sensory fibers get from the nasociliary nerve (V1) to the eyeball?

Answer 39

Nasociliary nerve is a branch of the ophthalmic division (V1) that synapses on the ciliary ganglion to pick up sensory innervation from the eyeball via the long and short ciliary nerves.

Question 40

How do post-ganglionic SNS nerves get to the eyeball and what muscles do they innervate?

Answer 40

They move through the sympathetic root to synapse on the otic ganglion and head to eyeball. Once there, they innervate the dilator papillae (for constriction)

Question 41

How do the postganglionic PSNS fibers get to the eyeball and what do they innervate?

Answer 41

The post-ganglionic PSNS fibers receive innervation from the pre-ganglionic PSNS fibers that passed through the motor root to synapse at the ciliary ganglion. The post-ganglionics travel through the short ciliary nerves to get into the eyeball and innervate the sphincter papillae and ciliary muscles.

Question 42

What do the somatic motor fibers that pass through the inferior division of CN III innervate?

Answer 42

Innervate 3 extraocular muscles: Inferior rectus, medial rectus and inferior oblique.