Orbit

Question 1

how many bones in the orbit

Answer 1

7

Question 2

2 bones forming roof of orbit

Answer 2

frontal bone

lesser wing of sphenoid

Question 3

2 bones forming lateral wall of orbit

Answer 3

zygomatic bone

greater wing of sphenoid

Question 4

3 bones forming floor of orbit

Answer 4

zygomatic bone
maxillary bone
palatine bone

Question 5

4 bones forming medial wall of orbit

Answer 5

maxillary
lacrimal
sphenoid
ethmoid

Question 6

what is the lamina papyracea

Answer 6

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

Question 7

3 orbital openings

Answer 7

optic foramen
superior orbital fissure (SOF)
inferior orbital fissure

Question 8

where is the optic foramen and what does it transmit

Answer 8

within lesser wing of sphenoid

transmits optic nerve and ophthalmic artery into middle cranial fossa

Question 9

where is the SOF and what are the 2 parts

Answer 9

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

Question 10

what does the superior part of the SOF contain

Answer 10

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

Question 11

what does the inferior part of the SOF contain

Answer 11

CNIII
nasociliary nerve (CNV1)
CNVI

Question 12

where is the inferior orbital fissure and 3 things it contains

Answer 12

between maxilla and greater wing of sphenoid bone

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

Question 13

what is the annulus of Zinn

Answer 13

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

Question 14

what 4 things run through the annulus of Zinn

Answer 14

CNII
CNIII
CNVI
nasociliary nerve

Question 15

what does retrobulbar anaesthetic block do

Answer 15

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

Question 16

where is the orbital septum located

Answer 16

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

Question 17

what is the orbital septum

Answer 17

membranous sheet that forms the fibrous part of the eyelids

Question 18

most common cause of unilateral and bilateral axial proptosis in adults

Answer 18

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

Question 19

2 phases of TED

Answer 19

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

inactive fibrotic phase - involves extraocular muscles and connective tissues

Question 20

3 risk factors for TED

Answer 20

smoking
female
HLA-DR3 and HLA-B8

Question 21

pathophysiology of TED

Answer 21

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

Question 22

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

Answer 22

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

Question 23

what is Dalrymple sign in TED

Answer 23

lid retraction

Question 24

what is von Graefe sign in TED

Answer 24

lid lag on downgaze

Question 25

what is Kocher sign in TED

Answer 25

'staring' appearance

Question 26

usual order of EOMs affected in TED (restrictive myopathy)

Answer 26

``` inferior rectus (IR) medial rectus (MR) superior rectus (SR) levator palpebrae lateral rectus (LR) ```

Question 27

1 rare clinical feature in TED

Answer 27

choroidal folds

Question 28

3 investigations for TED

Answer 28

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

Question 29

what does CT/MRI usually show in TED

Answer 29

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

Question 30

3 classifications of TED

Answer 30

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

Question 31

2 general measures for managing TED

Answer 31

smoking cessation | achieve euthyroid status

Question 32

5 ways to manage TED mild disease

Answer 32

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

Question 33

3 ways to manage TED moderate-severe

Answer 33

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

Question 34

5 times surgery is indicated in TED moderate-severe

Answer 34

``` after inflammatory phase subsides cases of optic neuropathy significant proptosis persistent diplopia severe lid retraction ```

Question 35

3 complications and associations with TED

Answer 35

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

Question 36

when to suspect dysthyroid optic neuropathy

Answer 36

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

Question 37

treatment of dysthyroid optic neuropathy

Answer 37

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

Question 38

3 ways to manage exposure keratopathy

Answer 38

lubricants surgery e.g. tarsorrhaphy botox injections

Question 39

what is preseptal cellulitis

Answer 39

infection of soft tissues anterior to orbital septum

Question 40

what is orbital cellulitis

Answer 40

infection of soft tissues posterior to orbital septum