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Binocular Vision > mechanical limitations - MEH > Flashcards

mechanical limitations - MEH Flashcards

1
Q

define a mechanical limitation

A

Restriction of ocular motility casued by elements within the orbit which interfere with muscle contraction and relaxation preventing movement

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2
Q

when you have a mechanical limitation what is duction equal to?

A

version

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3
Q

what does duction = version mean?

A

eye does not move when the other eye is occluded (i.e not an underaction)

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4
Q

what is a leash?

A

restraint interfering with muscle function

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5
Q

what are the 2 types of leash?

A

direct or indirect

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6
Q

what is a leash also known as ?

A

tether

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7
Q

what is a direct leash?

A

tight or shortened muscle/tendon

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8
Q

OM is limited when gaze is directed … from the leash (direct leash)

A

away

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9
Q

OM is limited when gaze is directed … the leash (indirect leash)

A

towards

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10
Q

what is an indirect leash?

A

blocking movement

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11
Q

examples of an indirect leash?

A

retinal explant or adhesions between the conjunctiva and orbit following trauma

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12
Q

characteristics of mechanical restrictions

A

1.+ve forced duction test
2.restriction of the globe
3.reversal of deviation in opposite gazes
4.limited muscle sequalae (steps 1&2)

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13
Q

what is thyroid eye disease also known as?

A

graves ophthalmopathy

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14
Q

there is an increased prevalence of co-existing autoimmune disorders in those with TED. what other condition should you consider?

A

myasthenia gravis

TED : autoimmune disease in which the eye muscles and fatty tissue behind the eye become inflamed

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15
Q

what is the pathology of TED?

A
  • inflammatory process causes EOM belly to become enlarged
  • this causes fibrosis leading to limited eye movement
  • increased amount of soft tissue leads of proptosis
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16
Q

what does NO SPECS stand for?

A

1.No signs or symptoms
2.Only signs, no symptoms
3.Soft tissue involvement (signs & symptoms)
5.Proptosis
6.Extraocular muscle involvement
7.Corneal involvement
8.Sight loss (optic nerve involvement)

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17
Q

what is NO SPECS?

A

grades for clinical severity

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18
Q

how long does the active period of TED last for?

A

2 years

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19
Q

when is treatment given for TED?

A

within the active phase

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20
Q

what is important to remember about NO SPECS?

A

does not provide a means of distinguishing inflammatory progressive from non-inflammatory stationary

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21
Q

name the clinical characteristics of TED?

A
  • inflamamtory signs of the eye and orbit
  • conjunctival injection sometimes over the site of rectus muscle insertion
  • chemosis
  • lid oedema
  • exophthalmos
    OVER TIME:
  • EOM become restricted and fibrotic
  • diplopia due ot asymmetrical limitations of OM
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22
Q

name some examination signs of TED?

A
  • upper lid retraction
  • reduced blinking freq
  • lid lag on downgaze
  • staring appearance
  • exophthalmos
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23
Q

what increased the risk of TED by 7x?

A

smoking

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24
Q

what is the HES investigation of TED?

A

thyroid function tests (TSH, T3 , T4 levels)
CT scans and MRI scans useful in active disease (esp in unilateral proptosis to exclude orbital tumour)

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25
Q

why is VA affected in TED?

A

optic nerve gets compressed by grossly enlarged EOM
corneal involvement due to exposure

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26
Q

what are important tests to do in someone with TED?

A

VAs, cover test and colour vision testing

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27
Q

what is revealed on cover test? TED

A

hypotropia (due to IR fibrosis)
excyclotorsion (tight IR) esp on attempted elevation
eso devation (due to limited abduction caused by MR fibrosis)
potential AHP

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28
Q

what is a commonly found deviation on cover test?

A

eso + hypo

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29
Q

key points of ophthalmic management?

A
  1. presevation of sight = priority therefore monitor vision
    watch for stabilisation of OM
  2. centralise and enlarge field of BSV therefore give prisms where appropriate and bangerter foil on glasses/patch
30
Q

4 types of medical management of TED?

A

topical therapy
high dose steroids
radiotherapy treatment
immunosuppressants

31
Q

what is ‘topical therapy’ for TED?

A

artificial tears and decongestants
taping eyes closed at night
tinted glasses
selenium supplement

32
Q

how would topical therapy help inTED?

A

useful for conjunctival injection and chemosis

33
Q

how do high dose steroids help in TED?

A

reduce inflammation —> reduce pressure on ON

34
Q

what treatment can you give alongside steroids?

A

radiotherapy

35
Q

when do you give radiotherapy treatment for TED?

A

early stages of the disease - to help with peristant inflammation in active stage

36
Q

how does immunosuppressive therapy help?

A

improves congestive changes

37
Q

what are the 3 types of surgical management available for TED?

A

decompression surgery
strabismus surgery
lid surgery

38
Q

when is decompression surgery considered?

A

cosmesis or px’s who have failed to respond to steroids and radiotherapy

39
Q

how does strabismus surgery help in TED?

A

recession MR / IR to imporve OM and correct cosmetic defect

40
Q

what causes orbital blow out fracture?

A

blunt trauma to orbits by an object >5cm

41
Q

what are the 2 effects of trauma?

A

soft tissue injury and bony injury

42
Q

what does ‘soft tissue injury’ mean?

A

no involvement of oribital bones

43
Q

what does soft tissue injury cause?

A

oedema and haemorrhage

44
Q

what is the hydraulic theory of bony injuries?

A

increased hydraulic pressure —> fractures of orbital plates at weak points
+ prolapse of orbital soft tissue into the maxillary sinus

45
Q

are there external signs of injury in paediatric groups with orbital floor fracture?

A

very little

46
Q

what is a blow out fracture called in paeds?

A

white eyed blow out fracture

47
Q

signs/symptoms pf white-eyes blow out fracture?

A

limited eye movement and dip

48
Q

if you have a blow out fracture before 18 years old, have the bones cracked or shattered?

A

cracked

49
Q

what is the most common type of fracture?

A

orbital floor fractue

50
Q

what may happen alongside an orbital floor fracture>?

A

harmorrhage or peripheral nerve damage - weak IR

51
Q

symptoms of orbital floor fracture?

A

diplopia (vertical)
pain (on attempted eye movement AWAY from the fracture - trapped tissue)
reduced VA (occasionally)

52
Q

signs of orbital floor fracture?

A

limitation of OM
infraorbital anaesthesia
enophthalmos
oedema and ecchymosis of the periorbital tissues - black eye
epistaxis (nose bleed)
subcutaneous air
dramatic eye closure

53
Q

what causes a limitation of OM in an orbital floor fracture?

A

oedema
entrapment of tissue
herniation of tissue
displacement of globe

54
Q

why would you have infraorbital anaesthesia in orbital floor fracture?

A

direct trauma to maxillary branch of trigeminal nerve
(loss of sensation to the ipsilateral cheek + upper teeth)

55
Q

what is subcutaneous air?

A

acummulation of air in connective tissue spaces
may make noise when you push on the orbit due to the prescence of air bubbles

56
Q

what radiological investigations woyld you want to carry out?

A

CT scan and Xray

57
Q

what clinical investigations would you want to do in someoen with orbital floor fracture?

A

OM
CT
Hess and field of BSV

58
Q

what is MAXFAX management?

A

if there are signs of recovery leave without surgery (spontaneous resolution of dip is common)
swelling may reduce within a few weeks

59
Q

after a white-eye blow out fracture, when do you do surgery?

A

2/3 days post injury

60
Q

when would you operate on an orbital floor fracture within 2 weeks??

A

IF THERE IS :
- tissue entrapment (shown on CT or +ve FDT)
- enopthalmos of >3mm
- orbital floor defect >50%

61
Q

when would you consider strabismus surgery after orbital floor fracture?

A

if dip does not resolve

62
Q

which eye do you operate on when carrying out strabismus surgery?

A

unaffected eye

63
Q

when is surgery more effective?

A

before fibrosis and scarring of tissue into the fracture site

64
Q

are there long-term affects following orbital floor fracture?

A

yes

65
Q

what are the common signs of TED?
1. upper lid retraction
2. reduced blink rate
3. lid lag on downgaze
4. exophthalmos
5. all of the above

A
  1. all of the above
66
Q

TED is not exacerbated by:
1. radio-iodine treatment of hyperthyroidism
2. development of hypothyroidism after treatment of hyperthyroidism
3. smoking
4. males

A
  1. males
67
Q

which of the following statements are incorrect about TED?
1. can cause ophthalmoplegia
2. more common in males than females
3. autoimmune disorder
4. smoking can exasperate the symptoms

A
  1. more common in males than females
68
Q

an 18 year old boy presents folloiwng an injury whereby a friends knee went into his eye whilst playing football. He is diagnosed with a Right blow out fracture. Which of the following statements are correct with regards to this diagnosis?

  1. he has diplopia worse on upgaze
  2. evident enopthalmos
  3. he has oedema and ecchymosis of the periorbital tissues
  4. nose bleed
  5. all of the above
A
  1. all of the above
69
Q

surgery for a blow out fractureis advised on the following in less than 2 weeks. Which of the following statements is incorrect?
1. +ve FDT
2. CT evidence of tissue entrapment
3. enophthalmos of <3mm
4. orbital floor defects of greater than 50%

A
  1. enophthalmos of <3mm ( meant to be enophthalmos >3mm)
70
Q

who is TED more common in?

A

females>males
hyperthyroid px’s
can occur in hypothyroidism/euthyroid px’s

71
Q

which muscles are most commonly affected in TED?

A

IR first
then MR
then SR

Binocular Vision (30 decks)

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