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14. Head and Neck > 5. The Orbit and the Eye > Flashcards

5. The Orbit and the Eye Flashcards

1
Q

What are the borders of the orbit?

A

Roof - frontal and sphenoid
Floor - maxilla, zygomatic, and palatine
Medial - ethmoid, maxilla, and lacrimal
Lateral - zygomatic and sphenoid

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2
Q

Which bones are involved in medial and inferior wall fractures of the orbit?

A

Medial wall fractures - ethmoidal and sphenoidal sinus

Inferior wall fractures - maxillary sinus

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3
Q

What is a blow out fracture of the orbit?

A

The orbit walls and contents are displaced. There is muscle entrapment, diplopia, and infection.

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4
Q

What is enopthalmos?

A

Depression of the eye, opposite of exophthalmos.

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5
Q

What can cause the eyeball to be pushed out of the orbit?

A

Infraorbital bleeding, pulsatile.

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6
Q

What goes through the optic canal?

A

The optic nerve.

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7
Q

What goes through the superior fissure, lateral to medial?

A

Large french teenagers sit numb in anticipation of sweets.
Lacrimal nerve, frontal nerve, trochlear nerve (CN IV), superior branch of oculomotor nerve (CN III), nasociliary nerve, inferior branch of oculomotor nerve (CN III), abducens nerve (CN VI), opthalmic veins, sympathetic nerves.

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8
Q

What is the covering of the optic nerve (CN II)?

A

Pia, arachoid, and dura maters of meninges so continuous with the brain.

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9
Q

What is a danger with infection of the orbit?

A

It can spread, tracking backwards along the meninges to the brain -> meningitis.

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10
Q

What are the extraocular muscles?

A

Superior recti, inferior recti, medial recti, lateral recti, superior oblique, inferior oblique, levator palpebrae superioris.

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11
Q

What are the actions of the four recti extraocular muscles?

A

Superior - look up.
Inferior - look down.
Medial - look medial.
Lateral - look lateral.

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12
Q

What are the actions of the two oblique extraocular muscles?

A

Superior - look down.

Inferior - look up.

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13
Q

What is the action of the levator palpebrae superioris?

A

Lifes upper eyelid.

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14
Q

What are the innervations of the extraocular muscles?

A

LR6SO4R3
Lateral rectus - CN VI abducens
Superior oblique - CN IV trochlear
all the Rest - CN III oculomotor

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15
Q

How does abducens nerve palsy present?

A

Loss of innervation to lateral rectus so unable to move eye laterally (abduct pupil) so pupil is fully adducted due to unopposed pull of medial rectus.

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16
Q

What can cause abducens nerve palsy?

A

Fractures involving orbit or cavernous sinus.

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17
Q

How does trochlear nerve palsy present?

A

Loss of innervation to superior oblique so unable to look eye down when eye is adducted.

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18
Q

What can cause trochlear nerve palsy?

A

Orbital fractures or stretching of the nerve during its course around the brainstem.

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19
Q

How does oculomotor nerve palsy present?

A

Loss of innervation to rest of the extraocular muscles. Superior eyelid droop in ptosis as there is loss of innervation to levator palpebrae superioris and unopposed activity of orbicularis oculi. Pupil is fully dilated and non reactive due to loss of innervation of sphincter pupillae and unopposed action of dilator pupillae. So the eye is down and out due to unopposed action of lateral rectus and superior oblique.

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20
Q

What can cause oculomotor nerve palsy?

A

Fractures involving the cavernous sinus or aneurysms.

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21
Q

What is the blood supply to the eye?

A

Opthalmic artery - branch of internal carotid artery.

Central artery of the retina - branch of opthalmic artery, end artery.

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22
Q

What does obstruction of the central artery of the retina lead to?

A

Instant and total blindness.

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23
Q

What is the venous drainage of the eye?

A

Superior and inferior opthalmic veins (exit via superior orbital fissure and drain into cavernous sinus).
Central vein of the retina drains into cavernous sinus directly or via opthalmic veins.

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24
Q

What does occlusion of the central vein of the retina lead to?

A

Slow, painless loss of vision.

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25
Q

What are the roles of the eyelids?

A

Protect the cornea and eyeball from injury and keep cornea moist by covering it with lacrimal fluid.

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26
Q

What is the conjunctiva?

A

The lining of the inner surface of the eyelid.

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27
Q

What strengthens the eyelids?

A

Tarsal plates - dense bands of connective tissue that contain tarsal glands, which produce secretions that lubricate edges of eyelids and prevent them from sticking when closed.

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28
Q

What does the lacrimal gland secrete?

A

Lacrimal fluid (tears) = watery physiological saline containing bacteriocidal lysozyme enzyme.

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29
Q

What is the purpose of lacrimal fluid?

A

Moistens and lubricates the surfaces of conjunctiva and cornea. It provides nutrients and dissolved oxygen to cornea.

30
Q

Where is the lacrimal gland?

A

In a fossa on superolateral part of the orbit.

31
Q

What do lacrimal ducts do?

A

Conduct lacrimal fluid from gland to conjunctival sac.

32
Q

What do lacrimal canaliculi do?

A

Drain lacrimal fluid from lacrimal lake to lacrimal sac as they’re at medial angle of eye.

33
Q

What does the nasolacrimal duct do?

A

Conveys lacrimal fluid to inferior nasal meatus (inferior to inferio nasal concha).

34
Q

How does the eyelid open?

A

Levator palpebrae superioris (oculomotor nerve CN III) assisted by superior tarsal muscles (sympathetic innervation).

35
Q

How does the eyelid close?

A

Orbicularis oculi (facial nerve CN VII).

36
Q

What are the three layers of the eyeball?

A

Outer protective layer, middle vascular layer, inner retina layer.

37
Q

What is the outer protective layer of the eyeball made of?

A

Sclera - fibrous and provides attachment for extraocular muscles, white and relatively avascular.
Cornea - transparent and avascular, nourishment from lacrimal glands and vascular beds, sensitive CN V1.

38
Q

What is the middle vascular layer of the eyeball made of?

A

Choroid - red of eye.
Ciliary body - anterior muscle thickening which attaches to and focuses lens. Process secretes aqueous humor into anterior chamber.
Iris - thin diaphragm, aperture is pupil, PSNS contract sphincter pupillae, SNS contracts dilator pupillae, rich blood vessels.

39
Q

What is the inner retina layer of the eyeball made of?

A

Optic part - photosensitive, neural and pigmented layer.

Non-visual part - anterior.

40
Q

What are the parts of the retina?

A

Fundus, macula, optic disc.

41
Q

What is the fundus of the retina?

A

Posterior of eye, seen with a fundoscope/opthalmoscope.

42
Q

What is the macula of the retina?

A

Fovea centralis, the dark spot.

43
Q

What is the optic disc?

A

The blind spot, where there is convergence of sensory fibres.

44
Q

What is myopia?

A

Short/near sighted so image is focused in front of the retina.

45
Q

What is hyeropia/hypermetropia?

A

Long/far sighted so image is focused behind the retina.

46
Q

What is presbyopia?

A

Far sight due to age-related changes of lens.

47
Q

What is aqueous humor produced by?

A

Ciliary process.

48
Q

Where does aqueous humor drain?

A

Into scleral venous sinus via trabecular meshwork.

49
Q

What is the purpose of aqueous humor?

A

Controlling intraocular pressure, glaucoma is raised intraocular pressure from blocked outflow of aqueous humor.

50
Q

How does the lens compensate for near vision?

A

Accommodation. PS activity in CN III so sphincter like contraction of ciliary muscle so lens fatter.

51
Q

How does the lens compensate for far vision?

A

No PS activity to ciliary muscles so lens stretches to be flatter. Thickens with age.

52
Q

What is the role of vitreous humor?

A

Holds retina in place.

53
Q

What are the two types of light cells in the retina?

A

Rods - low light, black and white.

Cones - bright light, colour vision.

54
Q

What are the afferent and efferent fibres of the corneal reflex?

A

Afferent: opthalmic branch of trigeminal nerve (CN V1)
Efferent: temporal and zygomatic branches of facial nerve (CN VII), contraction of orbicularis oculi -> blink.

55
Q

What can loss of corneal reflex lead to?

A

Corneal ulceration.

56
Q

What is mydriasis and what can cause it?

A

Dilation of the pupil. From under-activity of PSNS -> lack of innervation to sphincter pupillae. Or over-activity of SNS -> increased innervation of dilator pupillae.

57
Q

What is glaucoma and what can result from it?

A

Outflow of aqeous humor through scleral venous sinus is blocked so pressure builds up in anterior and posterior chambers of the eye. Blindness results if the central artery of the retina is compressed.

58
Q

What is presbyopia?

A

During ageing, the lens becomes harder and more flattened so the focusing power of the lens decreases.

59
Q

What is cataracts?

A

Loss of transparency of the lens from areas of opaqueness.

60
Q

How can cataracts be treated?

A

Cataract extraction and intra-ocular lens implant.

61
Q

What is retinal detachment?

A

Blow to the eye may cause detachment of the retina causing flashes of light or specks floating in front of eye and eventually blindness.

62
Q

What is coloboma?

A

Absence of a section of the iris from a birth defect.

63
Q

What is hyphema?

A

Haemorrhage within the anterior chamber of the eyeball from blunt force trauma to the eyeball.

64
Q

What is Horner’s syndrome?

A

Interruption of cervical sympathetic trunk causing absence of sympathetically stimulated functions on the ipsilateral side of the head: miosis (constriction of pupil), ptosis (drooping superior eyelid), vasodilation (redness and increased temperature), anhydrosis (absence of sweating).

65
Q

What is exopthalmos?

A

Protrusion of eye.

66
Q

What are the causes of exopthalmos?

A

Bilateral in Graves disease.

Unilateral in aneurysm or haematoma.

67
Q

What are the effects of raised intracranial pressure on the eye?

A

Compression of optic nerve so blood vessels to retina also compressed and blindness. Papilloedema from vein occlusion before artery occlusion.

68
Q

What is red eye?

A

Bloodshot eye from trauma, allergy, infection, or increased pressure.

69
Q

What is a meibomian cyst?

A

Blocked tarsal gland lying behind the eyelash within the eyelid.

70
Q

What is a stye?

A

Infection of the sebaceous gland at the base of the eyelash.

14. Head and Neck (11 decks)

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