Misaligned And Wobbly Eyes Flashcards
What is strabismus?
Squint
How is strabismus classified.
Infantile (concomitant)
Acquired (incomitant)
Describe infantile strabismus
Manifest (tropia)
Intermittent
Near
Concomitant - no limitation of movement
Describe acquired strabismus
Latent (phoria)
Constant
Distance
Incomitant - limitation of movement
What are the 2 types of incomitant strabismus?
Paretic - nerve palsy
Restrictive - mechanical restriction to muscle eg. Thyroid, tumour
What is esotropia?
Eye points inwards (convergent)
What muscle is not working in esotropia?
Lateral rectus
What is exotropia?
Eye points outwards (divergent)
What muscle is not working in exotropia?
Medial rectus
What is hypertropia?
Eye points upwards
What is hypotropia?
Eye points downwards
What muscles are not working in hypertropia?
Inferior rectus
Superior oblique
What muscles are not working in hypotropia?
Superior rectus
Inferior oblique
Causes of incomitant strabismus (paretic)
Supranuclear - dorsal midbrain
Inter nuclear - INO
Nuclear/nerve - 3rd, 4th, 6th palsies
Neuromuscular - myasthenia
Myopathies/myositis
Causes of incomitant strabismus (restrictive)
Thyroid eye disease
Orbital mass
Orbital wall fracture
Summarise constant strabismus
Full eye movements
Typically early childhood
Only some have double vision
Thypically bemign
No investigations normally
Often glasses help, may need surgery
Summarise incomitant strabismus
Limitation of eye movements
Acquired later in life
Typically will have diplopia
May be serious
Tend to need investigation
Prisms and surgery
Describe the cover test for strabismus
used to determine if manifest strabismus (heterotropia) is present
- ask patient to focus on an object in the distance
- cover one eye and observe the other
- no shift in fixation of uncovered eye = orthotropic (normal alignment)
- shift in fixation = heterotropia
repeat on other eye
Describe the cover-uncover/alternate cover test
used to differentiate if a misalignment is either a tropia or a phoria
if cover test shows no tropia, this test is to see if there is phoria (latent strabismus)
examiner occludes one eye for approximately 1-2 seconds, then quickly removes the occluder to restore binocular vision
then observe the previously occluded eye for refixation movement
if a phoria is present, this eye will move back to being orthotropic (straight-looking) to re-establish sensory fusion with the other eye
How can you tell if a strabismus is incomitant?
incomitant = limitation of movement
test eye movements in all directions
What is saccadic testing useful for?
(fast eye movements)
useful for:
- supranuclear/internuclear disorders
- spotting subtle paresis
- testing saccadic pathways
How does a 3rd nerve palsy affect the eye? (incomitant)
ptosis
down and out pupil
dilated pupil
abduction intact
How does a 4th nerve palsy affect the eye? (incomitant)
torsion (tilt)
compensatory head tilt
hypertropia
impaired depression (in adduction)
How does a 6th nerve palsy affect the eye? (incomitant)
esotropia
reduced abduction
ipsilateral face turn
