Session 5 - Eyeball and Orbit

Question 0

What are the main fissures and canals in the orbit canal and what runs through then?

Answer 0

Optic canal - optic nerve
Superior orbital canal - lacrimal, Trochlear, frontal, oculomotor and Abducens nerve and superior opthalmic vein.
Inferior orbital canal - infraorbital nerve
Fossa for lacrimal sac

Question 1

What bones form the roof, floor and medial and lateral walls of the orbit?

Answer 1

Roof - Frontal bone, sphenoid bone
Floor - Zygomatic bone, maxillary bone
Medial - Nasal bone, Lacrimal bone, Maxillary bone
Lateral - Zygomatic bone, Sphenoid

Question 2

Describe the structure of the optic nerve:

Answer 2

Optic nerve surrounded by pia, arachnoid and dura mater. These are continuous with the brain and could be a source of spread of infection.
Contains the central artery and vein.

Question 3

What clinical sign would you see in the eyes if there is raised intracranial pressure?

Answer 3

Papilloedema

Question 4

What areas of the orbit are more likely to be fractured?

Answer 4

Medial and inferior walls

Question 5

What areas can be involved in fractures of the orbit?

Answer 5

Inferior wall fracture - maxillary sinus

Medial wall fracture - ethmoidal and sphenoidal sinus

Question 6

What are the muscles of eye movements?

Answer 6

Superior, medial, lateral and inferior rectus muscles

Superior oblique and inferior oblique

Question 7

Which nerves supplies the muscles of eye movement?

Answer 7

CN III Oculomotor nerve - Inferior oblique, medial, superior and inferior rectus.
CN IV - Trochlear nerve - Superior oblique
CV VI - Abducens nerve - Lateral rectus

Question 8

What are the movements of the inferior oblique muscle?

Answer 8

Move eyes to look up and out

Abduction and extorsion (lateral rotation)

Question 9

What is the action of the superior oblique?

Answer 9

Primary - intorsion - internal rotation
Secondary - depression in adducted position e.g. Reading a book
Tertiary - abduction

Question 10

What is the blood supply to the orbit?

Answer 10

Opthalmic artery (branch of internal carotid)
Central artery branches off to supply the retina
If blocked causes blindness

Question 11

What is the venous drainage of the orbit?

Answer 11

Superior and inferior orbital veins which exit via the supraorbital fissure and drain into the cavernous sinus.
The central vein of the retina either drains directly into the cavernous sinus or into the opthalmic veins.
Blindness occurs gradually and is slow and painless.
Infection can spread to the brain via the veins.

Question 12

What are some of branches of the opthalmic artery?

Answer 12

Central retinal artery
Lacrimal artery
Posterior ciliary artery
Muscular branch of extraoccular arteries

Question 13

What is the danger triangle?

Answer 13

An area where infections can spread from the face to the brain via the facial vein via the superior and inferior opthalmic veins to the cavernous sinus.

Question 14

What are the consequences of spread of infection from the face to the brain?

Answer 14

Cavernous sinus thrombosis
Meningitis
Brain abscess

Question 15

What is the purpose of the eyelids?

Answer 15

Protect the eye from light and injury

Prevent corneal drying, through controlled spread of lacrimal fluid

Question 16

What are the layers of the eyelid?

Answer 16

Skin 
Areolar tissue 
Fibres of orbicularis oculi 
Levator palpebrae superioris  
Superior tarsus - dense connective tissue 
Tarsal glands - secrete oil (dry eye) 
Ciliary glands - sebaceous glands (stye) 
Palpebrae conjuctiva

Question 17

What is the corneal reflex for?

Answer 17

Protects corneal drying out
In expectation of contact
Corneal irritation or contact (perceived as pain)

Question 18

What nerves are involved in the blink reflex?

Answer 18

CN Vi - sensory

CN VII - motor action

Question 19

What muscles are involved in closing the eyelids?

Answer 19

Orbicularis oculi

Question 20

What muscles are involved in opening the eyelids?

Answer 20

Levator palpaebrae superioris

Superior tarsal muscles - smooth muscle of upper eyelid

Question 21

How is the eye affected in Bells Palsy?

Answer 21

Paralysis of orbicularis oculi
Loss of corneal and blink reflex
Dry eyes
Likely lead to infection

Question 22

What signs do you see in the eye if CNIII is paralysed?

Answer 22

Dropping of the upper eyelid ptosis

Only partial ptosis as superior tarsal muscle is still functional

Question 23

What innervates the superior tarsal muscle?

Answer 23

Sympathetic fibres

Question 24

What are the symptoms of Horner’s Syndrome?

Answer 24

Partial ptosis
Miosis - pupillary construction
Hemifacial anhydrosis

Question 25

What causes Horner’s Syndrome?

Answer 25

Damage to the sympathetic trunk

Symptoms occur on the ipsilateral side.

Question 26

What nerve causes tear production?

Answer 26

Parasympathetic division of the facial nerve CNVII

Question 27

Describe lacrimation:

Answer 27

Lacrimal fluid is released from lacrimal gland on the lateral upper eyelid. The eyelid closes from lateral to medial pushing the lacrimal fluid to the medial side where they collect in the lacrimal lake where they move via the lacrimal canal to the lacrimal sac down into the naso lacrimal duct where it can exit via the nasal cavity.