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Ophthalmology > Anatomy of the Orbit > Flashcards

Anatomy of the Orbit Flashcards

1
Q

How many bones make up the orbit of the eye?

A

7

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2
Q

Which bones make up the orbit of the eye?

A
  1. Frontal
  2. Zygomatic
  3. Maxilla
  4. Nasal
  5. Sphenoid
  6. Ethmoid
  7. Lacrimal
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3
Q

Which aspect of the frontal bone allows passage of the supraorbital nerve?

A

Supraorbital notch

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4
Q

Which bone contains the optic canal?

A

Sphenoid bone

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5
Q

The optic canal is the _____ of the bony orbit

A

The optic canal is the apex of the bony orbit

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6
Q

What is the main function of the optic rim?

A

Protects the eye from direct trauma

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7
Q

Which bones mainly comprise the following regions of the bony orbit?

a) Roof
b) Medial wall
c) Lateral wall
d) Floor

A

a) Roof - Frontal bone
b) Medial wall - Ethmoid bone
c) Lateral wall - Sphenoid bone
d) Floor - Maxilla

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8
Q

Which aspects of the bony orbit are particuarly weak and thin?

A
  1. Medial wall (ethmoid)
  2. Orbital floor (maxilla)
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9
Q

Which type of fractures are the medial wall and floor of the orbit particuarly susceptible to?

A

Blowout fractures

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10
Q

Which main problems arise with an orbital blowout fracture?

A
  1. Trapped orbital contents
  2. Infraorbital NVB damage
  3. Sensory deficit of facial skin
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11
Q

Which areas does the infraorbital nerve innervate?

A
  1. Ala of nose
  2. Skin around maxilla (lower eyelid to upper lip)
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12
Q

Why may a fractured zygoma result in double vision?

A
  1. Fractured zygoma rotates medially
  2. Suspensory ligament attaches to zygoma laterally
  3. Eye lowered to orbital floor as tension reduced
  4. Diplopia occurs
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13
Q

What is the name given to the muscle surrounding the orbit of the eye?

A

Orbicularis oculi

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14
Q

The orbicularis oculi is split into which two parts?

A
  1. Orbital part
  2. Palpebral part
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15
Q

Which type of secretion do the tarsal (eyelid) glands secrete?

A

Lipid secretion

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16
Q

What is the orbital septum and what is its function?

A

Sheet of fascia

Aids in preventing spread of infection

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17
Q

What is the name of the muscle(s) which elevates the upper eyelid?

A
  1. Levator palpebrae superioris
  2. Superior tarsal (Müller’s*) muscle

*Do not confuse with orbitalis muscle (also known as Müller’s muscle)

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18
Q

Which muscle is primarily responsible for:

a) Gently closing eyes
b) Screwing up eyes

A

a) Orbicularis oculi (palpebral aspect) - Gently closing eyes
b) Orbicularis oculi (orbital aspect) - Screwing up eyes

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19
Q

Which cranial nerve innervates the orbicularis oculi?

A

Facial nerve

(CN VII)

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20
Q

Which structure covers the iris?

A

Cornea

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21
Q

What is the limbus?

A

Corneal/scleral junction

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22
Q

Which glands are responsbile for tear production?

A

Lacrimal

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23
Q

Where does lacrimal fluid drain within the eye?

A

Puncta (inferior and superior)

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24
Q

What is the conjunctival fornix?

A

Loose arching folds connecting the conjunctival membrane lining the inside of the eyelid with the conjunctival membrane covering the eyeball

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25
Q

The conjunctiva does not cover which part of the eye?

A

Cornea

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26
Q

What is the pathway of lacrimal fluid drainage?

A
  1. Lacrimal puncta
  2. Canaliculi
  3. Lacrimal sac
  4. Nasolacrimal duct
  5. Nasal cavity
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27
Q

What is the approximate diameter of the eye?

A

25mm

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28
Q

What are the 3 main layers of the eye?

A
  1. Fbrous layer
  2. Vascular layer (uvea)
  3. Inner layer (retina)
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29
Q

The fibrous layer of the eye is comprised of which two main components?

A
  1. Sclera
  2. Cornea
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30
Q

The vascular layer (uvea) of the eye is comprised of which 3 parts?

A
  1. Iris
  2. Ciliary body
  3. Choroid
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31
Q

The inner layer of the eye (retina) is comprised of which 3 main parts?

A
  1. Macula
  2. Optic disc
  3. Retina
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32
Q

What is the anterior segment of the eye?

A

The part of the eye anterior to the lens

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33
Q

The anterior segment of the eye is split into which two chambers?

A
  1. Anterior (between cornea and iris)
  2. Posterior (between iris and suspensory ligaments)
34
Q

Both the anterior chamber and posterior chamber of the anterior segment of the eye contain which type of fluid?

A

Aqueous humour

35
Q

What is the key function of the choroid of the eye?

A

Nutrition and gas exchange

36
Q

What is the posterior segment of the eye?

A

2/3rd of the eye posterior to the lens

37
Q

What does the posterior segment of the eye contain?

A

Vitreous body which contains vitreous humour

38
Q

What is the iridocorneal angle?

A

Angle formed by the iris and cornea to allow drainage of aqueous humour from the eye

39
Q

Why is the posterior segment of the eye a common location for “floaters”?

A

Vitreous humour is composed of a gel-like substance which may include areas of liquefaction and clumps of collagen fibres which are the “floaters”

N.b. This is pathological and not normal

40
Q

A cataract is a _________ of the lens

A

A cataract is a clouding of the lens

41
Q

Where is aqueous humour produced?

A

Ciliary processes of ciliary body

42
Q

Which type of muscle is the ciliary body composed of?

A

Smooth

43
Q

Describe the circulation of aqueous humour

A
  1. Secreted from ciliary body
  2. Nourishes lens in posterior chamber
  3. Passes through pupil to anterior chamber
  4. Nourishes cornea
  5. Reabsorbed into scleral venous sinus (Canal of Schlemm) at iridocorneal angle
44
Q

What may be the outcomes of raised intra-ocular pressure?

A
  1. Ischaemia of retina
  2. Glaucoma
45
Q

Which artery gives off artieries which supply the eye?

A

Internal carotid artery

46
Q

Which artery supplies the contents of the orbit?

A

Opthalmic artery

47
Q

Which branches does the opthalmic artery give off?

A
  1. Ciliary arteries
  2. Central artery of retina
  3. Nasal cavity branches
  4. Forehead/scalp branches
48
Q

Which vesses travel within the optic nerve?

A
  1. Central artery of the retina
  2. Central vein of the retina
49
Q

Why is it a major problem if the central artery of the retina became occluded?

A

It is an end artery so is the only blood supply to the retina

50
Q

Describe the venous drainage of the orbit

A

Superior and inferior opthalmic veins drain anteriorly via the facial vein and posteriorly via the caverous sinus

51
Q

What is the “Danger triangle”?

A

A triangular area on the face covering the nose and upper lip

Infection (e.g. from squeezing acne) can enter the facial vein and travel posteriorly via the inferior/superior opthalmic veins to the canverous sinus

Here, meningeal infection can manifest itself

52
Q

What is the fundus?

A

The posterior area of the retina where light is focused

53
Q

Which three parts comprise the fundus?

A
  1. Optic disc
  2. Macula
  3. Fovea
54
Q

The optic disc is the point of formation for what?

A

Optic nerve

55
Q

What is the blind spot?

A

Created due to the postition of the optic nerve and lack of photoreceptive cells in the area

56
Q

What is the macula?

A

The area of the fundus with the greatest density of cones

57
Q

What is the fovea?

A

Depression in the centre of the macula

(Area of most acute vision)

58
Q

List the layers of the retina from posterior to anterior

A
  1. Photoreceptor cells
  2. Ganglion cells
  3. Axons of ganglion cells

(Retinal veins and arteries lie posterior to the retina)

59
Q

Loss of a specific area of a visual field in one eye may be due to ischaemia in which vessel type?

A

Retinal artery/vein

(not central artery/vein)

60
Q

Monocular blindness is due to what?

A

Complete interruption of flow of the central retinal artery or vein

61
Q

Light from objects in the right visual field is processed where?

A

Left primary visual cortex

62
Q

Light from objects in the lower visual field is processed where?

A

Upper part of primary visual cortex

63
Q

What comprises the right visual field?

A
  1. Nasal retina of left eye
  2. Temporal retina of right eye
64
Q

How many extraocular muscles are there?

A

7

65
Q

What are the three types of extraocular muscles?

A
  1. 4 Rectus muscles
  2. 2 Oblique muscles
  3. 1 Levator palpebrae superiorus
66
Q

What are the 4 rectus muscles?

A
  1. Superior rectus
  2. Inferior rectus
  3. Medial rectus
  4. Lateral rectus
67
Q

Where do all the rectus muscles originate?

A

Common tendinous ring

68
Q

Where do all the rectus muscles insert?

A

Sclera

69
Q

What is the innervation of the lateral rectus muscle?

A

Abducens nerve (CN VI)

(Remember LR6 SO4 AO3)

70
Q

What is the innervation of the superior oblique muscle?

A

Trochlear nerve (CN IV)

(Remember LR6 SO4 AO3)

71
Q

Excluding the lateral rectus and superior oblique muscles, what is the innervation of the extraocular muscles?

A

Oculomotor nerve (CN III)

(Remember LR6 SO4 AO3)

72
Q

What are the three axes which the eye can rotate upon?

A
  1. Vertical axis (adduct/abduct)
  2. Transverse axis (elevate/depress)
  3. AP axis (lateral/medial rotation)
73
Q

Which extraocular muscles do not have secondary movements?

A
  1. Medial rectus
  2. Lateral rectus
74
Q

Which eye movement is the lateral rectus responsible for?

A

Abduction

75
Q

How can the functioning of the superior rectus be tested?

A

When the eye is in abduction, the superior rectus can only elevate

76
Q

How can the functioning of the inferior rectus be tested?

A

When in abduction, the inferior rectus can only depress

77
Q

Which movement is the medial rectus responsible for?

A

Adduction

78
Q

How can the functioning of the inferior oblique be tested?

A

When in adduction, the inferior oblique can only elevate

79
Q

How can the functioning of the superior oblique be tested?

A

When in adduction, the superior oblique can only depress

80
Q

What is “pure elevation”?

A

Synergistic action of the superior rectus and inferior oblique resulting in elevation of eyes

(the muscles are antagonists as rotators)

81
Q

What is “pure depression”?

A

Synergistic action of the superior oblique and inferior rectus to depress eyes

(antagonists as adductors/abductors)

Ophthalmology (15 decks)

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