mechanical limitations - MEH Flashcards
define a mechanical limitation
Restriction of ocular motility casued by elements within the orbit which interfere with muscle contraction and relaxation preventing movement
when you have a mechanical limitation what is duction equal to?
version
what does duction = version mean?
eye does not move when the other eye is occluded (i.e not an underaction)
what is a leash?
restraint interfering with muscle function
what are the 2 types of leash?
direct or indirect
what is a leash also known as ?
tether
what is a direct leash?
tight or shortened muscle/tendon
OM is limited when gaze is directed … from the leash (direct leash)
away
OM is limited when gaze is directed … the leash (indirect leash)
towards
what is an indirect leash?
blocking movement
examples of an indirect leash?
retinal explant or adhesions between the conjunctiva and orbit following trauma
characteristics of mechanical restrictions
1.+ve forced duction test
2.restriction of the globe
3.reversal of deviation in opposite gazes
4.limited muscle sequalae (steps 1&2)
what is thyroid eye disease also known as?
graves ophthalmopathy
there is an increased prevalence of co-existing autoimmune disorders in those with TED. what other condition should you consider?
myasthenia gravis
TED : autoimmune disease in which the eye muscles and fatty tissue behind the eye become inflamed
what is the pathology of TED?
- inflammatory process causes EOM belly to become enlarged
- this causes fibrosis leading to limited eye movement
- increased amount of soft tissue leads of proptosis
what does NO SPECS stand for?
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)
what is NO SPECS?
grades for clinical severity
how long does the active period of TED last for?
2 years
when is treatment given for TED?
within the active phase
what is important to remember about NO SPECS?
does not provide a means of distinguishing inflammatory progressive from non-inflammatory stationary
name the clinical characteristics of TED?
- 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
name some examination signs of TED?
- upper lid retraction
- reduced blinking freq
- lid lag on downgaze
- staring appearance
- exophthalmos
what increased the risk of TED by 7x?
smoking
what is the HES investigation of TED?
thyroid function tests (TSH, T3 , T4 levels)
CT scans and MRI scans useful in active disease (esp in unilateral proptosis to exclude orbital tumour)
why is VA affected in TED?
optic nerve gets compressed by grossly enlarged EOM
corneal involvement due to exposure
what are important tests to do in someone with TED?
VAs, cover test and colour vision testing
what is revealed on cover test? TED
hypotropia (due to IR fibrosis)
excyclotorsion (tight IR) esp on attempted elevation
eso devation (due to limited abduction caused by MR fibrosis)
potential AHP
what is a commonly found deviation on cover test?
eso + hypo
key points of ophthalmic management?
- presevation of sight = priority therefore monitor vision
watch for stabilisation of OM - centralise and enlarge field of BSV therefore give prisms where appropriate and bangerter foil on glasses/patch
4 types of medical management of TED?
topical therapy
high dose steroids
radiotherapy treatment
immunosuppressants
what is ‘topical therapy’ for TED?
artificial tears and decongestants
taping eyes closed at night
tinted glasses
selenium supplement
how would topical therapy help inTED?
useful for conjunctival injection and chemosis
how do high dose steroids help in TED?
reduce inflammation —> reduce pressure on ON
what treatment can you give alongside steroids?
radiotherapy
when do you give radiotherapy treatment for TED?
early stages of the disease - to help with peristant inflammation in active stage
how does immunosuppressive therapy help?
improves congestive changes
what are the 3 types of surgical management available for TED?
decompression surgery
strabismus surgery
lid surgery
when is decompression surgery considered?
cosmesis or px’s who have failed to respond to steroids and radiotherapy
how does strabismus surgery help in TED?
recession MR / IR to imporve OM and correct cosmetic defect
what causes orbital blow out fracture?
blunt trauma to orbits by an object >5cm
what are the 2 effects of trauma?
soft tissue injury and bony injury
what does ‘soft tissue injury’ mean?
no involvement of oribital bones
what does soft tissue injury cause?
oedema and haemorrhage
what is the hydraulic theory of bony injuries?
increased hydraulic pressure —> fractures of orbital plates at weak points
+ prolapse of orbital soft tissue into the maxillary sinus
are there external signs of injury in paediatric groups with orbital floor fracture?
very little
what is a blow out fracture called in paeds?
white eyed blow out fracture
signs/symptoms pf white-eyes blow out fracture?
limited eye movement and dip
if you have a blow out fracture before 18 years old, have the bones cracked or shattered?
cracked
what is the most common type of fracture?
orbital floor fractue
what may happen alongside an orbital floor fracture>?
harmorrhage or peripheral nerve damage - weak IR
symptoms of orbital floor fracture?
diplopia (vertical)
pain (on attempted eye movement AWAY from the fracture - trapped tissue)
reduced VA (occasionally)
signs of orbital floor fracture?
limitation of OM
infraorbital anaesthesia
enophthalmos
oedema and ecchymosis of the periorbital tissues - black eye
epistaxis (nose bleed)
subcutaneous air
dramatic eye closure
what causes a limitation of OM in an orbital floor fracture?
oedema
entrapment of tissue
herniation of tissue
displacement of globe
why would you have infraorbital anaesthesia in orbital floor fracture?
direct trauma to maxillary branch of trigeminal nerve
(loss of sensation to the ipsilateral cheek + upper teeth)
what is subcutaneous air?
acummulation of air in connective tissue spaces
may make noise when you push on the orbit due to the prescence of air bubbles
what radiological investigations woyld you want to carry out?
CT scan and Xray
what clinical investigations would you want to do in someoen with orbital floor fracture?
OM
CT
Hess and field of BSV
what is MAXFAX management?
if there are signs of recovery leave without surgery (spontaneous resolution of dip is common)
swelling may reduce within a few weeks
after a white-eye blow out fracture, when do you do surgery?
2/3 days post injury
when would you operate on an orbital floor fracture within 2 weeks??
IF THERE IS :
- tissue entrapment (shown on CT or +ve FDT)
- enopthalmos of >3mm
- orbital floor defect >50%
when would you consider strabismus surgery after orbital floor fracture?
if dip does not resolve
which eye do you operate on when carrying out strabismus surgery?
unaffected eye
when is surgery more effective?
before fibrosis and scarring of tissue into the fracture site
are there long-term affects following orbital floor fracture?
yes
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
- all of the above
TED is not exacerbated by:
1. radio-iodine treatment of hyperthyroidism
2. development of hypothyroidism after treatment of hyperthyroidism
3. smoking
4. males
- males
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
- more common in males than females
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?
- he has diplopia worse on upgaze
- evident enopthalmos
- he has oedema and ecchymosis of the periorbital tissues
- nose bleed
- all of the above
- all of the above
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%
- enophthalmos of <3mm ( meant to be enophthalmos >3mm)
who is TED more common in?
females>males
hyperthyroid px’s
can occur in hypothyroidism/euthyroid px’s
which muscles are most commonly affected in TED?
IR first
then MR
then SR
