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Semester 3-AHNNA > Lecture 12&13-Eye > Flashcards

Lecture 12&13-Eye Flashcards

1
Q

Which bones form the roof of the orbital cavity?

A

Frontal bone and lesser wing of sphenoid

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2
Q

Which bones form the floor of the orbital cavity?

A

Maxilla, palatine and zygomatic bones

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3
Q

Which bones form the medial wall of the orbital cavity?

A

Ethmoid, maxilla, lacrimal and sphenoid bones

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4
Q

Which bones form the lateral wall of the orbital cavity?

A

Zygomatic and greater wing of sphenoid

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5
Q

What are the three openings at the apex of the orbital cavity?

A

Superior orbital fissure
Inferior orbital fissure
Optic canal

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6
Q

Which two walls of the orbital cavity are the weakest?

A

Medial wall and floor

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7
Q

What is an orbital blow out fracture?

A

Partial herniation of orbital contents through one wall due to sudden increase in intra-orbital pressure

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8
Q

Why can’t the eye roll up in a blow out fracture?

A

Orbital contents and blood prolapse into maxillary sinus and the fracture site can trap the inferior oblique muscle which rolls the eye up

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9
Q

What are the signs and symptoms of an blow out fracture?

A
  • periorbital swelling
  • pain
  • diplopia
  • impaired vision
  • anaesthesia over affected cheek
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10
Q

Why does an orbital blow out fracture cause anaesthesia of the affected cheek?

A

Cutaneous branches of CN Vb (infra-orbital branch) runs through the floor of the orbit and innervates the cheek and lower eye so fracture of the floor can damage this branch

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11
Q

What are tarsal plates?

A

Fibrous CT skeleton of the eyelid which gives it shape

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12
Q

What are the contents of the orbital cavity?

A
  • lacrimal apparatus
  • nerves and blood vessels
  • eyeball
  • orbital fat
  • extra-ocular muscles
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13
Q

What is the orbital septum?

A

Thin sheet of fibrous tissue originating from the orbital rim which blends with the tendon of levator palpebrae superioris and tarsal plates

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14
Q

What does the orbital septum separate?

A

Intra-orbital contents from eyelid fat and orbicularis oculi muscle

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15
Q

What is periorbital cellulitis?

A

Cellulitis of orbital structures secondary to infection from bites, periorbital trauma, sinuses

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16
Q

What are the complications of periorbital cellulitis?

A

Abscess

Spread of infection intracranially -> cavernous sinus thrombosis

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17
Q

Which is worse out of pre-septal and post-septal cellulitis and why?

A

Post-septal because infection is beyond the septum and can infect contents of the orbital cavity -> abscess whereas pre-septal is more localised as it can’t spread past the septum

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18
Q

Where do veins of the orbit drain to?

A

Cavernous sinus, pterygoid venous plexus and facial veins

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19
Q

Where are Meibomian glands and what do they do?

A

In the tarsal plates

Secrete an oily substance onto the edges of the eyelid which stops tears from drying

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20
Q

What are the glands of Zeis?

A

Hair follicle glands

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21
Q

What can a blocked gland of Zeis lead to and how can it become blocked?

A

Styes which are red and painful

Caused by infections (usually staph)

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22
Q

What is a Meibomian cyst?

A

Blockage of Meibomian gland - not infected or painful

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23
Q

What is the conjunctivae and what is its function?

A
  • Transparent membrane covering the front of the eye

- Secretory mucosa lubricating the conjunctival and corneal surfaces

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24
Q

What is conjunctivitis?

A

Inflammation of conjunctiva due to infection

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25
Q

What is subconjunctival haemorrhage?

A

Haemorrhage from blood vessels

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26
Q

What is the main arterial supply to the orbit?

A

Ophthalmic artery (branch of ICA) and its branches

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27
Q

Which vein drains the orbit?

A

Ophthalmic vein which drains into cavernous sinus, pterygoid plexus and facial vein

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28
Q

Which nerve provides sensory innervation to the eye?

A

Ophthalmic branch of trigeminal nerve

29
Q

Which nerve provides special sensory innervation to the eye?

A

Optic nerve

30
Q

What are the motor nerves to the muscles of the eye?

A

Oculomotor, trochlear and abducens

31
Q

How is the eyeball maintained in its position?

A

Suspensory ligament, rectus muscles, orbital fat

32
Q

What are the three layers of the eyeball?

A
  • outer protective layer
  • middle vascular layer
  • inner layer (retina)
33
Q

Describe the outer layer of the eyeball

A
  • Tough fibrous sclera, continues anteriorly as transparent cornea and continuous with dural sheath covering optic nerve at back of the eye.
  • Conjunctiva covers sclera, extends up to edge of cornea (limbus) and reflected onto inner surface of eyelids
34
Q

Describe the middle layer of the eyeball

A
  • choroid which continues anteriorly as ciliary body and iris
  • ciliary body consists of ciliary process and muscle and connects choroid with iris
35
Q

Describe the inner layer of the eyeball

A
  • retina has inner photosensitive layer and outer pigmented layer (melanin)
  • melanin absorbs scattered light and reduces reflection
36
Q

Describe the photosensitive area of the retina

A

Has rods and cones - cones for visual acuity and colour and rods for vision in low sensitive light

37
Q

Where in the retina can the most cones be found?

A

Fovea in the macula of the retina

38
Q

How does the anterior chamber communicate with the posterior chamber of the eye?

A

Through the pupil

39
Q

What produces aqueous humour?

A

Ciliary processes within ciliary body in the posterior chamber of the eye

40
Q

What does aqueous humour do?

A

Supports the shape of the eyeball and nourishes the lens and cornea

41
Q

How does the aqueous humour drain?

A

Through the irido-corneal angle into the canal of Schlemm via trabecular meshwork and back into venous circulation

42
Q

How can glaucoma cause blindness?

A

Increased intra-ocular pressure -> damage and death of optic nerve -> vision impairment or blindness

43
Q

What is open-angle glaucoma?

A

Blockage within trabecular meshwork which develops painlessly over time

44
Q

How can open-angle glaucoma be treated?

A

Eye drops to reduce production of aqueous humour or increase drainage eg beta blockers

45
Q

What is close-angle glaucoma?

A
  • Irido-corneal angle is narrowed -> increased intra-ocular pressure
  • Sudden onset painful, red eye, blurred vision, fixed semi-dilated pupil, nausea and vomiting
46
Q

How can close-angle glaucoma be treated?

A

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

47
Q

When is the accommodation reflex of the eye needed?

A

To see near objects because the light rays are more divergent so more refraction is needed to bring near objects into focus

48
Q

Describe the three things that happen in the accommodation reflex

A
  • automatic constriction of the pupil so light passes through the centre of the lens
  • convergence of the eyes so both retinae are focused on the object
  • lens becomes more biconcave as the suspensory ligament loosens
49
Q

What is presbyopia and how does it develop?

A

As we age, lens becomes stiffer and less able to change shape so can’t focus on near objects

50
Q

What is cataracts?

A

Progressive opacity within the lens

51
Q

Which extra-ocular muscles are attached to the fibrous ring around the optic canal?

A

Superior, inferior, medial and lateral rectus muscles

52
Q

Where do the superior and inferior oblique muscles attach?

A

Bony walls of the orbit

53
Q

Which nerve innervates most of the extra-ocular muscles and what are the exceptions?

A
  • Oculomotor nerve

- exceptions: lateral rectus innervated by abducens nerve and superior oblique innervated by trochlear nerve (LR6SO4)

54
Q

What does lateral rectus do?

A

Moves the eye laterally

55
Q

What does medial rectus do?

A

Moves the eye medially

56
Q

Which muscles move the eyes directly upwards?

A
  • superior rectus and inferior oblique

- secondary action of SR is adduction and secondary action of IO is abduction so these cancel out so the eye is central

57
Q

Which muscles move the eye directly downwards?

A
  • inferior rectus and superior oblique
  • secondary action of IR is adduction and secondary action of SO is abduction so these actions cancel out so that the eye is central
58
Q

In which direction does superior oblique roll the eyeball?

A

Out and down, depresses, abducts and intorts the eyeball

59
Q

In which direction does inferior oblique roll the eyeball?

A

Up and out, extorts, elevates and abducts the eyeball

60
Q

From which direction do the rectus muscles approach the eyeball?

A

From the apex of the orbit

61
Q

How can CN III damage occur and what can it lead to?

A
  • aneurysm
  • innervates LPS -> complete ptosis if damaged
  • dilation of pupil (sphincter pupillae damaged)
62
Q

How can CN IV damage occur and what can this lead to?

A
  • congenital trauma

- superior oblique muscle affected -> extortion, up and in direction of eye

63
Q

What can CN VI damage cause?

A

Unopposed pull of medial rectus in affected eye

64
Q

How can you isolate the action of superior oblique?

A

Look medially then down

65
Q

How can you isolate the action of inferior rectus?

A

Look laterally then down

66
Q

How can you isolate the action of inferior oblique?

A

Look medially then up

67
Q

How can you isolate the action of superior rectus?

A

Look laterally then up

68
Q

What is papilloedema?

A

Swelling of the optic disc secondary to raised intra-cranial pressure

69
Q

What is blepharitis?

A

Inflammation of the eyelid

Semester 3-AHNNA (15 decks)

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