Pupillary Reflexes Flashcards
What is the pathway for pupil constriction
light hits retina - retinal ganglion cell fires down retinal ganglion axons to the lateral geniculate nucleus (in thalamus) and the pre-tectal area - pretectal area fires to both acessory oculomotor nuclei (1 on either side), these then send axons to preciliary ganglion fibres, that synapse in the ciliary ganglion, sending post ganglionic fibres to the ciliary muscle which synapse and cause contriction
what is the edinger-westphal nucleus
accessory oculomotor nucleus - the parasympathetic nucleus of CN3
What cranial nerves are tested by pupillary reflexes
CN2 + 3
What is the sympathetic pathway for pupil dilation
hypothalamic fibres travel to T1 and enter the sympathetic chain, they then ascend to the superior cervical ganglion and synapse with post-ganglionic sympathetic fibres
post-ganglionic fibers situated along internal carotid and travel with opthalmic artery
in the orbit, fibres pass through the ciliary ganglion synapsing with the long ciliary nerve to reach eyeball
in eyeball fibres innervate dilator pupillae muscle
what does the tectospinal tract regulate
reflexive motor adjustement in response to visual stimuli
What is RAPD
pupil dilation when a bright light is swung from the unaffected eye to the affected eye (in reality it is just constricting less but it looks like its dilating)
what causes RAPD
optic nerve ischaemia optic neuritis compression asymmetric glaucoma central retinal arter/vein ischemia/occlusion large retinal detachment
what is horners syndrome
sympathetic dysfunction due to upper thoracic compression of the sympathetic chain
what is a common cause of horners syndrome
pancoast tumour
what are PRIMARY causes of horners syndrome
CNS disease
cervical comression
diabetic neuropathy
what are secondary causes of horners syndrome
cervical rib pancoast tumour aortic/carotid aneurysm opical TB neck trauma lymphadenopathy
what is the classic triad of symptoms of horners syndrome
unilateral ptosis (eyelid drop), miosis (pupil constriction) and anhydrosis (dry skin)
how do you diagnose horners syndrome
non-dilation using cocaine 4% or dilation on apraclonidine 0.5%
what are the symptoms of 3rd nerve palsy
ptosis
dilated pupil
eyes looking down and out
what are the causes of 3rd nerve palsy
brainstem tumour CVA demyelination skull base haematoma cavernous sinus tumour/fistula/inflammation orbit tumour/trauma/inflammation vascular palsy surgical lesion uncal herniation
what is a feature of a vascular 3rd nerve palsy
pupils are spared
what is adies pupil
pupil dilation
absent light response
slow near response (no light reflex, slow but present near response)
slow tendon reflexes
what causes adies pupil
ciliary ganglion problems
what is the usual demographic for adies pupil
young females
how do you diagnose adies pupil
pilocarpine will constrict the affected pupil
what is argyll robinson pupil
neurosyphillis causing small irregular pupils and light-near dissociation (can accommodate better than light response)
what is traumatic mydriasis
dilated pupils in response to blunt trauma damaging the sphincter iris muscle
what is posterior synechiae
following intraocular inflammation, the iris pigment epithelium adheres to the lens resulting in an irregularly shaped pupil
what do you see in the accomodation reflex
convergence and contriction
what does anisocoria mean
asymmetric pupils
What is defined as asymmetric pupils
when they’re different by >1mm
what is the common inital presentation of CN3 palsy
diplopia when focusing horizontally to the left/right
what are some common causes of diplopia
myasthenia gravis
graves
Cranial nerve palsy
what is a common symptom of myasthenia gravis
symptoms occur at the end of the day
what extracranial nerves exist in the cavernous sinus
lacrimal nerve
CN3
maxillary and opthalmic division of the trigeminal
CN4
where are the nuclei of CN3
medial midbrain
how can you tell a nuclear Cn3 palsy and an infranuclear CN3 palsy
other eye normal = infranuclear
what is adies pupil + decreased tendon reflexes called
homes-adies syndrome
how do you fix mydriasis
contact lens that mimics iris position of normal light in the other eye to minimise ‘glare phenomenon ‘
what are some causes of the inflammation preceding posterior synechiae
corneal ulcer (most common) uveitis/anterior iritis endophalmitis
how do you treat posterior synechiae
dilate pupil and check for choroidal inflammation
give steroids + dilating agents to prevent sticking
why are dilating agents helpful in posterior synechiae
prevent ciliary muscle spasm which causes most of the pain, as well as allowing aqeuous build up behind the iris to drain causing secondary glaucoma
why does RAPD occur
slowed rate of conduction
what should the top differential be for an abnormally enlarged pupil
adies pupil
what is the most likely diagnosis of an abnormally enlarged pupil with near-light dissociation , and what is the next management step
adies, check tendon reflexes
whats the top differential of an abnormally enlarged pupil with no near-light dissociation
CN3 palsy
whats the top differential of an abnormally enlarged pupil with no near-light dissociation and normal eye movements
traumatic myadriasis
whats the top differential of an abnormally enlarged pupil with no near-light dissociation and abnormal movements
CN3 palsy
