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ESA3 - Head and Neck > The Eye > Flashcards

The Eye Flashcards

1
Q

What forms the roof of the bony orbit?

A

Frontal bone and lesser wing of the sphenoid

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2
Q

What separates the orbit from the anterior cranial fossa?

A

Frontal bone

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3
Q

What forms the floor of the bony orbit?

A

Maxilla, palatine and zygomatic bones

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4
Q

What forms the medial wall of the bony orbit?

A

Ethmoid, maxilla, lacrimal and sphenoid bones

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5
Q

What are the three main pathways by which structures can enter and leave the orbit?

A

1) Optic canal
2) Superior orbital fissure
3) Inferior orbital fissure

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6
Q

What does the optic canal convey?

A

Optic nerve and opthalmic artery

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7
Q

What does the superior orbital fissure convey?

A

CN III, CN IV, CN VI and the superior opthalmic vein

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8
Q

What does the inferior orbital fissure convey?

A

Maxillary nerve (branch of CN V), inferior opthalmic vein and sympathetic nerves

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9
Q

In a blowout fracture, where do orbital contents commonly herniate?

A

Ethmoid and maxillary sinuses as the medial and inferior walls of the orbit are the weakest

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10
Q

What are the three layers of the eyeball?

A

Fibrous, vascular and inner layers

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11
Q

What does the fibrous layer of the eyeball consist of?

A

Sclera and cornea

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12
Q

What does the vascular layer of the eyeball consist of?

A

1) Choroid (a layer of connective tissue and blood vessels that provides nourishment to the outer layers of the retina)
2) Ciliary body (attached to lens of the eye to control its shape)
3) Iris (has the pupil in the middle - between lens and cornea)

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13
Q

What does the inner layer of the eyeball consist of?

A

Retina

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14
Q

What does the retina consist of?

A

Neural layer - consists of photoreceptors

Pigmented layer - supports the neural layer

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15
Q

What marks the centre of the retina?

A

Macula

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16
Q

What does the macula contain?

A

Fovea - high concentration of light detecting cells

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17
Q

What is the fovea responsible for?

A

High acuity vision

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18
Q

What is the area that the optic nerve enters the retina known as?

A

Optic dic

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19
Q

What are the two fluid filled areas in the eye known as?

A

Anterior and posterior chambers

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20
Q

Where is the anterior chamber located?

A

Between cornea and iris

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21
Q

Where is the posterior chamber located?

A

Between iris and ciliary processes

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22
Q

What are the anterior and posterior chambers filled with?

A

Aqueous humor

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23
Q

What drains aqueous humor?

A

Trabecular meshwork - an area of tissue at the base of the cornea

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24
Q

What condition can result if the drainage of aqueous humor is obstructed?

A

Glaucoma

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25
Q

What is open angle glaucoma?

A

When the outflow of aqueous humor through the trabecular meshwork is reduced - causing a gradual reduction of the peripheral vision

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26
Q

What is closed angle glaucoma?

A

Where the iris is forced against the trabecular meshwork, preventing any drainage of aqueous humor (opthalmic emergency - can rapidly cause blindness)

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27
Q

How does the eyeball receive arterial blood?

A

Opthalmic artery - a branch of the ICA

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28
Q

Occlusion of which artery will quickly result in blindness?

A

Central artery of the retina (branch of opthalmic artery that supplies the internal surface of the retina)

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29
Q

What do the superior and inferior opthalmic veins drain into?

A

Cavernous sinus

30
Q

What is papilloedema?

A

Swelling of the optic disc - usually occurs secondary to raised ICP

31
Q

What do important anatomical relations of the orbit include?

A

Paranasal air sinuses, nasal cavity and anterior cranial fossa

32
Q

What are some complications of periorbital cellulitis?

A

Abscess formation and spread of infection intracranially -> cavernous sinus thrombosis

33
Q

How can periorbital cellulitis spread intracranially?

A

Opthalmic veins drain into cavernous sinus

34
Q

What causes a meibomian cyst?

A

Blockage of meibomian gland

35
Q

What is a stye?

A

Blockage of hair follicle glands

36
Q

What is the conjuctiva?

A

Transparent mucous membrane that produces mucus and tears - covers sclera and lines inside of eyelides (does not cover cornea)

37
Q

What nerve is responsible for general sensory from the eye?

A

Opthalmic division of CN V

38
Q

What nerve is responsible for special sensory vision from the retina?

A

Optic nerve (CN II)

39
Q

What nerves the motor nerves to muscles of the eye?

A

Oculomotor, trochlea, abducens

CN III, IV, VI

40
Q

What secretes aqueous humor?

A

Ciliary processes within ciliar body - flows from posterior chamber through pupil to anterior chamber to nourish lens and cornea

41
Q

What is the name of the angle that aqueous humor drains through?

A

Iridocorneal angle (between iris and cornea)

42
Q

Aqueous humor drains via trabecular meshwork into what?

A

Canal of Schlemm (venous channel draining into venous circulation)

43
Q

How many extraocular muscles are there?

A

Seven

44
Q

What are the extraocular muscles?

A

Superior rectus, inferior rectus, medial rectus, lateral rectus

Superior oblique, inferior oblique

Levator palpebrae superioris

45
Q

How many rectus muscles are there in the eye?

A

4 - superior, inferior, medial, lateral

46
Q

How many oblique muscles are there in the eye?

A

2 - superior and inferior

47
Q

What is the only muscle involved in raising the superior eyelid?

A

Levator palpebrae superioris (LPS)

48
Q

What is the name of the portion of levator palpebrae superioris that is smooth muscle and responds to the sympathetic nervous system?

A

Superior tarsal muscle

49
Q

What is the action of levator palpebrae superioris?

A

Raises the upper eyelid

50
Q

What innervates levator palpebrae superioris?

A

Oculomotor nerve (CN III)

Note - superior tarsal muscle which is within LPS is innervated by the SNS

51
Q

Horner’s syndrome refers to a triad of symptoms produced by damage to the sympathetic trunk in the neck. What are these 3 symptoms?

A

1) Partial ptosis (due to denervation of the superior tarsal muscle)
2) Miosis (due to denervation of dilator pupillae)
3) Anhydrosis on ipsilateral side of face (due to denervation of the sweat glands)

52
Q

What could Horner’s syndrome suggest?

A

Apical lung tumour, aortic aneurysm, thyroid carcinoma

53
Q

How many muscles control eyeball movements?

A

6 - rectus muscles and oblique muscles

54
Q

Where do the rectus muscles originate?

A

Common tendinous ring - surrounds the optic canal - and attach to the sclera

55
Q

What are the actions of superior rectus?

A

Mainly elevation

Also contributes to adduction and medial rotation

56
Q

What are the actions of inferior rectus?

A

Mainly depression

Also contributes to adduction and lateral rotation

57
Q

What are the actions of medial rectus?

A

Adduction of the eyeball

58
Q

What are the actions of lateral rectus?

A

Abduction of the eyeball

59
Q

What are the actions of superior oblique?

A

Depression, abduction and medial rotation of the eyeball

60
Q

What is the only muscle that acts on the eyeball to be innervated by the trochlear nerve?

A

Superior oblique

61
Q

What innervates superior oblique?

A

Trochlear nerve

62
Q

What is the only muscle that acts on the eyeball to be innervated by the abducens nerve?

A

Lateral rectus

63
Q

What innervates lateral rectus?

A

Abducens nerve

64
Q

What innervates the extraocular muscles?

A 
Oculomotor nerve (CN III) - mainly
Trochlear nerve (CN IV) - superior oblique
Abducens nerve (CN VI) - lateral rectus
65
Q

What position does the eyeball take if a patient has a CN III lesion?

A

Down and out - pulled laterally by lateral rectus and inferiorly by superior oblique (as they are innervated by other cranial nerves)

66
Q

What would a CN IV lesion do?

A

Paralyses superior oblique - diplopia and a head tilt away from the site of lesion

67
Q

What would a CN VI lesion do?

A

Paralyses lateral rectus - affected eye will be adducted by the resting tone of the medial rectus

68
Q

What the mnemonic to remember the innervation of the extraocular muscles?

A

LR6-SO4

Lateral rectus - CN VI
Superior oblique - CN IV

69
Q

What muscles are responsible for moving the eyes directly upwards?

A

Superior rectus and inferior oblique

70
Q

What muscles are responsible for moving the eyes directly downwards?

A

Inferior rectus and superior oblique

ESA3 - Head and Neck (17 decks)

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