Squints/Visual Acuity Flashcards
what is strabismus
malalignment of the eyes (squint)
what is ambylopia
lazy eye
what is a tropia
malalignment which is always there
what is a phoria
malalignment which only occurs some of the time
what is esotropia
convergent stabismus
quint where one or both eyes turn inwards
on cover test when the good eye is covered the other eye moves back out to assume a normal position
what is a extropia
divergent strabismus
outward deviation of an eye
on cover test when you cover the normal eye the bad eye will move back inwards
what do eco/esotropias do to vision
cause horizontal double vision
what is a hypertrophia
one eye is deviated up the way
when you cover the good eye the bad eye moves down
what is a hypotropia
one eye is deviated down the way
when you cover good eye the other eye moves up
what do hyper and hypotropias do to vision
cause vertical double vision
what eye movements should you do to check for tropias
get patient to look left, right and up into each corner then down into each corner
mark on diagram
100% - normal movement
0% - no movement
when would you do a cover test
to show small tropias which aren’t visible to the eye
on cover test the eye moves out- what is the deformity
esotropia
must have been in isotropic position before and is now moving out to a normal position bc it has to work harder with the good eye covered
on cover test the eye moves in - what is the deformity
exotropia
must have been exotropic position to start with and is now moved in to a normal position
causes of tropias
3rd nerve palsy
4th nerve palsy
6th nerve palsy
internuclear ophthalmoplegia
how does a 3rd nerve palsy present
eye is in ‘down and out’ position
superior oblique and lateral rectus are still working
eyelid droops due to lack of leaver palpibrae superiors innervation
no/slow pupillary light reflex
common causes of 3rd nerve palsy
microvascular tumour aneurysm MS congenital
what type of aneurysm most commonly causes a third nerve palsy
Posterior communicating artery aneurysm
how does a 4th nerve palsy present
paralysis of superior oblique (trochlear nerve palsy)
eye cannot move inferiomedially
therefore double vision occurs when looking down
head tilt is often seen to correct the double vision
causes of 4th nerve palsy
congenital - most common
microvascular
tumour
trauma
how does a 6th nerve palsy present
esotropia - paralysis of lateral rectus means eye turns inwards
cause of 6th nerve palsy
microvascular causes
raised ICP (compressing CNVI onto petrous tip of temporal bone)
tumour
congenital
what is internuclear opthalmoplegia
lesion in the longtidutinal fascicles (which is responsible to adducting one eye when the other abducts and vis versa)
most commonly caused by MS
how does internuclear ophthalmoplegia present
one eye cannot abduct and the other eye has nystagmus
