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Duke Elder exam > Orbit > Flashcards

Orbit Flashcards

1
Q

how many bones in the orbit

A

7

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2
Q

2 bones forming roof of orbit

A

frontal bone

lesser wing of sphenoid

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3
Q

2 bones forming lateral wall of orbit

A

zygomatic bone

greater wing of sphenoid

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4
Q

3 bones forming floor of orbit

A

zygomatic bone
maxillary bone
palatine bone

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5
Q

4 bones forming medial wall of orbit

A

maxillary
lacrimal
sphenoid
ethmoid

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6
Q

what is the lamina papyracea

A

paper-thin plate which covers the ethmoidal cells and forms a part of the medial wall - can act as a route of entry for infection from the ethmoid sinus

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7
Q

3 orbital openings

A

optic foramen
superior orbital fissure (SOF)
inferior orbital fissure

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8
Q

where is the optic foramen and what does it transmit

A

within lesser wing of sphenoid

transmits optic nerve and ophthalmic artery into middle cranial fossa

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9
Q

where is the SOF and what are the 2 parts

A

between greater and lesser wings of sphenoid - superior and inferior part

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10
Q

what does the superior part of the SOF contain

A

superior ophthalmic vein
lacrimal nerve (CNV1)
frontal nerve (CNV1)
CNIV

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11
Q

what does the inferior part of the SOF contain

A

CNIII
nasociliary nerve (CNV1)
CNVI

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12
Q

where is the inferior orbital fissure and 3 things it contains

A

between maxilla and greater wing of sphenoid bone

infraorbital nerve (CNV2) 
zygomatic nerve (CNV2) 
inferior ophthalmic vein
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13
Q

what is the annulus of Zinn

A

common tendinous ring surrounding the optic canal and inferior part of the SOF - marks the origin of the 4 recti muslces

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14
Q

what 4 things run through the annulus of Zinn

A

CNII
CNIII
CNVI
nasociliary nerve

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15
Q

what does retrobulbar anaesthetic block do

A

affects the nerves inside the common tendinous ring / annulus of Zinn

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16
Q

where is the orbital septum located

A

anterior to the orbit and extends from the orbit rims to the eyelid - marks the border between the periorbital (preseptal) and orbital (postseptal) regions

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17
Q

what is the orbital septum

A

membranous sheet that forms the fibrous part of the eyelids

18
Q

most common cause of unilateral and bilateral axial proptosis in adults

A

thyroid eye disease (TED) - usually associated with hyperthyroidism but can also involve hypo or euthyroid

19
Q

2 phases of TED

A

active inflammatory phase (months-years) - eyes red and painful

inactive fibrotic phase - involves extraocular muscles and connective tissues

20
Q

3 risk factors for TED

A

smoking
female
HLA-DR3 and HLA-B8

21
Q

pathophysiology of TED

A

sympathetic overstimulation of Müller muscle due to high levels of thyroid hormones causing eyelid retraction

fibroplastic deposition of glycosaminoglycans into the EOM producing oedema and eventual fibrosis of EOM

22
Q

3 things occurring in TED as a result of fibrosis of EOM

A

impaired movement of EOM (restrictive myopathy)

exophthalmos - which exposes the cornea causing dryness, irritation and exposure keratitis

lid retraction due to fibrosis of levator palpebrae

increased pressure on the optic nerve = optic neuropathy

impaired venous drainage = conjunctival and periorbital oedema and conjunctival injection

23
Q

what is Dalrymple sign in TED

A

lid retraction

24
Q

what is von Graefe sign in TED

A

lid lag on downgaze

25
Q

what is Kocher sign in TED

A

‘staring’ appearance

26
Q

usual order of EOMs affected in TED (restrictive myopathy)

A 
inferior rectus (IR) 
medial rectus (MR)
superior rectus (SR)
levator palpebrae 
lateral rectus (LR)
27
Q

1 rare clinical feature in TED

A

choroidal folds

28
Q

3 investigations for TED

A

thyroid function tests
imaging (CT/MRI if orbital decompression is planned)
visual field testing, especially if ON suspected

29
Q

what does CT/MRI usually show in TED

A

thickening of EOM bellies (most commonly IR and MR) with characteristic tendon sparing

30
Q

3 classifications of TED

A

severe sight threatening (optic neuropathy)
moderate-severe (exophthalmos >3mm, lid retraction >2mm and/or diplopia)
mild disease

31
Q

2 general measures for managing TED

A

smoking cessation

achieve euthyroid status

32
Q

5 ways to manage TED mild disease

A

watchful waiting
ocular lubricants
topical ciclosporin (reduce ocular irritation)
overnight lid taping (for mild exposure keratopathy)
selenium supplements

33
Q

3 ways to manage TED moderate-severe

A

IV methylprednisolone +/- oral prednisolone
orbital radiotherapy (can be used in combination with steroids)
surgery

34
Q

5 times surgery is indicated in TED moderate-severe

A 
after inflammatory phase subsides
cases of optic neuropathy 
significant proptosis 
persistent diplopia 
severe lid retraction
35
Q

3 complications and associations with TED

A

dysthyroid optic neuropathy - causes severe sight-threatening TED
exposure keratopathy
superior limbic keratoconjunctivitis (common)

36
Q

when to suspect dysthyroid optic neuropathy

A

changes in colour vision or VA with presence of optic disc swelling and RAPD

37
Q

treatment of dysthyroid optic neuropathy

A

IV steroids and orbital decompression (if unresponsive to IV steroids)

38
Q

3 ways to manage exposure keratopathy

A

lubricants
surgery e.g. tarsorrhaphy
botox injections

39
Q

what is preseptal cellulitis

A

infection of soft tissues anterior to orbital septum

40
Q

what is orbital cellulitis

A

infection of soft tissues posterior to orbital septum

Duke Elder exam (5 decks)

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