8) Anatomy of Orbit and Eyeball

Question 1

What is contained in the orbit?

Answer 1

Eyeball, its muscles, nerves, vessels and lacrimal apparatus

Question 2

What bones form the superior orbit?

Answer 2

Frontal and sphenoid

Question 3

What bones form the lateral orbit?

Answer 3

Zygomatic and sphenoid

Question 4

What bones form the medial orbit?

Answer 4

Ethmoid, maxillary, lacrimal and sphenoid

Question 5

What bones form the inferior orbit?

Answer 5

Maxillary and zygomatic

Question 6

What are the entrances to the orbit and through which bone?

Answer 6

Optic canal, superior orbital fissure and inferior orbital fissure
Sphenoid bone

Question 7

What are the vulnerable points of the orbit?

Answer 7

Inferior and medial walls are thin

Question 8

What are the 3 layers of the eyeball?

Answer 8

Outer fibrous
Middle vascular
Inner

Question 9

What does the outer fibrous layer consist of?

Answer 9

Sclera and cornea

Question 10

What does the middle vascular layer consist of?

Answer 10

Choroid, ciliary body and iris

Question 11

What forms the inner layer of the eyeball?

Answer 11

Retina

Question 12

What features can be seen in fundoscopy?

Answer 12

Optic disc - where optic nerve enters eye

Vessels, macula with fovea at centre

Question 13

How can you tell which eye is being examined by the fundus?

Answer 13

Optic disc is on nasal side

Question 14

What are the consequences of retinal detachment?

Answer 14

If left too long, cells of retina will die leading to partial blindness

Question 15

How can meningitis affect the eye and why?

Answer 15

Optic nerve is surrounded by meninges so inflammation can cause photophobia - discomfort or pain of light exposure

Question 16

What are the three chambers of the eye?

Answer 16

Anterior: cornea to iris
Posterior: iris to lens
Vitreous: filled with vitreous humour

Question 17

How does the aqueous humour drain?

Answer 17

Irido-corneal angle into canal of Schlemm via trabecular meshwork then into venous circulation

Question 18

What is glaucoma?

Answer 18

Obstruction in drainage of aqueous humour so intra-ocular pressure increases

Question 19

What are the consequences of untreated glaucoma?

Answer 19

Damage to optic nerve = vision impairment and blindness

Question 20

What is the cause of open angle glaucoma?

Answer 20

Blockage in trabecular meshwork, causing rise in intra-ocular pressure, cupping of optic disc and/or visual field loss

Question 21

What is the treatment for open angle glaucoma?

Answer 21

Reduction in production of aq. humour or surgery

Question 22

What is the cause of closed angle glaucoma?

Answer 22

Irido-corneal angle narrowed as access to trabecular meshwork is blocked off. Rapid rise in intra-ocular pressure

Question 23

How does closed angle glaucoma present?

Answer 23

Painful red eye, blurred vision, oval shaped pupil, hard eye

Question 24

What is the treatment for closed angle glaucoma?

Answer 24

Muscarinic eye drops, analgesia and drugs to reduce intra-ocular pressure

Question 25

Describe the iris:

Answer 25

Coloured and have sphincter and dilator pupillae muscles

Question 26

What structure are involved in changing lens shape?

Answer 26

Ciliary muscle fibres, suspensory ligaments and autonomic nerves

Question 27

What causes cataracts?

Answer 27

Degradation of proteins in lens

Question 28

What is the accommodation reflex?

Answer 28

Automatic contraction of pupil and convergence of eyes when suddenly focusing on a near object after a distant object

Question 29

What is presbyopia?

Answer 29

Impaired ability to accommodate

Question 30

What is the mechanism of the accommodation reflex?

Answer 30

Contraction of ciliary muscles causes loosening of suspensory ligament and lens becomes rounder

Question 31

What are the functions of the eyelids and lacrimal glands?

Answer 31

Preventing injury, foreign bodies, excessive light and dryness

Question 32

What gives eyelids their shape?

Answer 32

Tarsal plates (dense bands of CT)

Question 33

What is the difference between a Meibomian cyst and a stye?

Answer 33

Cyst - tarsal gland inflamm | Stye - pus in ciliary glands

Question 34

What muscles cause opening of eyelid?

Answer 34

``` Levator palpabrae superioris (CN III) Superior tarsal (sympathetic) (minor) ```

Question 35

How would an oculomotor lesion and Horner's syndrome differ in presentation (eyelid)?

Answer 35

Complete ptosis in CN III lesion | Partial in Horner's

Question 36

Describe the drainage of tears:

Answer 36

Lacrimal lake at medial angle of eye, then in lacrimal sac via lacrimal canal. Into nasal cavity by nasolacrimal duct

Question 37

What is the conjunctiva and its clinical relevance?

Answer 37

Film on top of cornea | Inflamed in conjunctivitis causing redness

Question 38

Describe the arterial supply to the eye:

Answer 38

ICA -> ophthalmic artery -> central retina artery

Question 39

Describe the venous drainage of the eye:

Answer 39

Central retinal vein -> superior ophthalmic vein -> cavernous sinus

Question 40

What is the innervation of the extra-ocular muscles?

Answer 40

LR6 SO4 R3

Question 41

Where do the recti muscles originate?

Answer 41

Common tendinous ring around optic canal

Question 42

Where do the oblique muscles arise?

Answer 42

Bony walls of orbit

Question 43

What does superior oblique travel through?

Answer 43

Trochlea (ligament sling)

Question 44

What is the movement of superior oblique?

Answer 44

Down and in

Question 45

What is the movement of inferior oblique?

Answer 45

Up and in

Question 46

What is the movement of superior rectus?

Answer 46

Up and out

Question 47

How would you test the eye muscles in isolation?

Answer 47

Line up gaze with line of attachment of muscle e.g. SR - look out then ask to move eye up

Question 48

How does a blow out fracture of the orbit present?

Answer 48

Blood in maxillary sinus Inferior rectus moves down so eye can't move upwards (tethered) Loss of sensation under eye, damage to infra-orbital nerve