6 - Eye and Orbit

Question 1

Which bones make up the roof, floor and lateral wall of the orbit?

Answer 1

Roof – orbital plate of frontal bone
Floor – orbital plate of maxillary bone
Lateral wall – greater wing of the sphenoid bone + zygomatic bone

Question 2

Which bones make up the medial wall of the orbit? (4)

Answer 2

Lacrimal bone
Orbital plate of ethmoid
Frontal process of maxilla
Lesser wing of sphenoid

Question 3

What foramen lie just superiorly and inferiorly to the orbit on the anterior surface of the skull?

Answer 3

supra-orbital foramen

infra-orbital foramen

Question 4

Which structures pass through the optic canal?

Answer 4

Optic nerve

Ophthalmic artery

Question 5

Which structures pass through the inferior orbital fissure?

Answer 5

(Zygomatic branch of the) maxillary division (V2) of trigeminal nerve
Infraorbital vessels

Question 6

Which structures pass through the superior orbital fissure?

Answer 6

(nerves involved in extrinsic muscle function)
Oculomotor
Trochlear
Ophthalmic division (V1) of trigeminal
Abducens
Ophthalmic veins (superior and inferior)
Sympathetic fibres

Question 7

Name the 4 recti muscles and state their origin and insertion.

Answer 7

Superior Rectus, Inferior Rectus, Lateral Rectus, Medial Rectus
Origin: common tendinous ring at the back of the eye
Insertion: 5 mm behind the corneal margin (onto the sclera)

Question 8

State the innervation of the 6 extrinsic eye muscles?

Answer 8

Lateral Rectus = Abducens (CN 6)
Superior Oblique = Trochlear (CN 4)
Medial Rectus, Superior Rectus, Inferior Rectus, Inferior Oblique = Oculomotor (CN 3)

Question 9

What are the 2 oblique muscle of the eye?

Answer 9

inferior and superior oblique muscles

Question 10

State the origin and insertion of the inferior oblique.

Answer 10

Origin: orbital surface of maxilla
Insertion: postero-lateral inferior quadrant of the globe

Question 11

State the origin and insertion of the superior oblique.

Answer 11

Origin: body of sphenoid
Insertion: via the trochlea to the postero-lateral superior quadrant of the globe

Question 12

Which muscle is responsible for elevating the eyelid?

Answer 12

Levator palpebrae superioris

Question 13

Where is the origin and insertion of the levator palpebrae superioris muscle?

Answer 13

Origin: lesser wing of sphenoid
Insertion: superior tarsal plate and skin of the eyelid

Question 14

Describe the innervation of the levator palpebrae superioris muscle

Answer 14

Oculomotor and sympathetic to smooth muscle

Question 15

Describe the isolated muscle action of the oblique muscles.

Answer 15

Superior oblique = depresses AND abducts

Inferior oblique = elevates AND abducts

Question 16

Describe the isolated muscle action of the superior and inferior recti.

Answer 16

Superior rectus = elevates AND adducts

Inferior rectus = depresses AND adducts

Question 17

Describe how you would test the muscle actions of medial rectus and lateral rectus

Answer 17

medial rectus - adduct
lateral rectus - abduct

NOTE: these are also the isolated muscle actions

Question 18

Describe how you would test the muscle actions of superior rectus and inferior rectus.

Answer 18

Superior rectus = make the patient abduct their eye and then elevate it
Inferior rectus = make the patient abduct their eye and then depress it

Question 19

Describe how you would test the muscle actions of superior oblique and inferior oblique.

Answer 19

Superior oblique = make the patient adduct their eye and then depress it
Inferior oblique = make the patient adduct their eye and then elevate it

Question 20

Which nerve axons make up the optic nerve?

Answer 20

Retinal ganglion cell axons

Question 21

What types of fibres are found within the oculomotor nerve?

Answer 21

Motor fibres to MR, SR, IR, IO and LPS
Parasympathetic fibres
The oculomotor nerve has two rami

Question 22

What types of fibres from the eye are found within the trochlear nerve?

Answer 22

motor fibres to SO

Question 23

What types of fibres from the eye are found within the abducens nerve?

Answer 23

motor fibres to LR

Question 24

What structure do the cranial nerves pass through before reaching the superior orbital fissure?
What is the clinical significance of this?

Answer 24

Cavernous sinus

Question 25

Where is the cavernous sinus?

Answer 25

either side of the sphenoid bone with folds dura on either side

Question 26

When passing through the cavernous sinus, the major of the nerve pass next to the wall. Which of the nerves passes through the middle?

Answer 26

Abducens (CN VI)

Question 27

What are the branches of the ophthalmic division of the trigeminal nerve? Which branch is biggest?

Answer 27

Nasociliary Lacrimal Frontal – this is the largest

Question 28

What are the branches of the branches of the ophthalmic division of the trigeminal nerve?

Answer 28

``` Lacrimal – no branches Nasociliary • Branch to ciliary ganglion • Ethmoidal • Infratrochlear Frontal • Supratrochlear • Supraorbital ```

Question 29

What limb of the autonomic nervous system is the ciliary ganglion involved in?

Answer 29

PARASYMPATHETIC

Question 30

Which fibres enter the ciliary ganglion and which fibres leave the ciliary ganglion?

Answer 30

Fibres entering the ciliary ganglion: preganglionic fibres in the inferior ramus of the oculomotor nerve Fibres leaving the ciliary ganglion: postganglionic fibres in the short ciliary nerves

Question 31

What do the fibres leaving the ciliary ganglion innervate?

Answer 31

Sphincter pupillae | Ciliary muscle

Question 32

What are the SIX branches of the ophthalmic artery?

Answer 32

``` Supratrochlear Supraorbital Lacrimal Ciliary Muscular branches Central artery of the retina ```

Question 33

Name the two ophthalmic veins and state where they drain.

Answer 33

Superior ophthalmic vein = cavernous sinus | Inferior ophthalmic vein = pterygoid plexus

Question 34

Describe the location of the lacrimal glands.

Answer 34

Anterolateral superior orbit

Question 35

Describe the innervation of the lacrimal glands

Answer 35

Parasympathetic secretomotor fibres of Facial Nerve (CN 7) from the pterygopalatine ganglion via the zygomaticotemporal and, finally, lacrimal nerves

Question 36

Where do the tears initially drain?

Answer 36

Lacrimal Sac

Question 37

Via which duct do the tears drain from the lacrimal sac and where does this duct empty?

Answer 37

Nasolacrimal duct – empties into the inferior nasal meatus

Question 38

What is Horner’s syndrome and how does it manifest itself in patients?

Answer 38

It is caused by a disorder of the sympathetic nerves in the brainstem or cervical region Presents as: • Ptosis • Miosis • Anhydrosis (lack of sweating around the eye)