Ophthalmology - Pupil Disorders Flashcards
What are circular muscles and dilator muscles responsible for?
Circular muscles
Pupil constriction - Parasympathetic stimulation - ACh
Fibres travel along CNIII
Dilator muscles
Pupil dilation - Sympathetic stimulation - Adrenaline
What can cause an irregular pupil shape?
CARATS
Coloboma
Anterior uveitis
Rubeosis iridis
Acute angle-closure glaucoma
Tadpole pupil
Sphincter muscle trauma
What causes a tadpole pupil?
Muscle spasm in part of the dilator muscle of iris
Temporary
Associated with migraines and Horner syndrome
List some causes of mydriasis (dilated pupil)
SHIT CAN
Stimulants e.g. cocaine
Holmes adie syndrome
ICP raised
Trauma
Congenital
Acute angle closure glaucoma
Nerve palsy III
Anticholinergics e.g. oxybutynin
List some causes of miosis (constricted pupil)
- Horner syndrome
- Cluster headaches
- Argyll-Robertson pupil (neurosyphilis)
- Opiates
- Nicotine
- Pilocarpine
What are the signs of third nerve palsy?
- Ptosis (drooping upper eyelid)
- Dilated non-reactive pupil
- Divergent strabismus (squint) in the affected eye, down and out position
Why do you get a down and out position of the eye in CNIII palsy?
All extraocular muscles except lateral rectus and superior oblique are controlled by CNIII
Superior oblique pulls the eye downwards and lateral rectus pulls the eye outwards
What causes ptosis in third nerve palsy?
Loss of function of levator palpebrae superioris
Why does CNIII compression cause a dilated, non-reactive pupil?
Parasympathetic fibres innervate circular muscles of the iris, compression causes a loss of constriction
Thefore unopposed dilation
Why does pupil sparing suggest microvascular complication?
Parasympathetic fibres are not compressed therefore due to :
- Diabetes
- Hypertension
- Ischaemia
What can cause compression of the oculomotor nerve?
- Tumour
- Trauma
- Cavernous sinus thrombosis
- Posterior communicating artery aneurysm
- Raised intracranial pressure
What does the oculomotor nerve pass through?
Cavernous sinus
Close to posterior communicating artery
What is Horner syndrome characterised by?
- Ptosis
- Miosis
- Anhidrosis (loss of sweating)
Can also have enopthalmos (sunken eye)
What is the path of sympathetic nerves?
Sympathetic nerves arise from the spinal cord in the chest as pre-ganglionics
Pre-ganglionics enter the sympathetic ganglion at the base of neck and exit as post-ganglionic nerves
Post-ganglionics travel with the ICA
What is the significance of anhidrosis in Horner syndrome?
Central lesions occur before nerves exit the spine,anhidrosis of :
- Arm
- Trunk
- Face
Pre-ganglionic lesions
Face
Post-ganglionic
Does not cause anhidrosis
What are the causes of Horner’s Syndrome?
4Ss 4Ts 4Cs
S-Sentral
Stroke
Multiple Sclerosis
Swelling (tumours)
Syringomyelia
T-Torso (pre-ganglionic)
Tumour (pancoast)
Trauma
Thyroidectomy
Top rib (cervical rib growing above first rib and clavicle)
C-Cervical (post-ganglionic)
Carotid aneurysm
Carotid artery dissection
Cavernous sinus thrombosis
Cluster headache
What is congenital Horner syndrome associated with?
Heterochromia
What can be used to test for Horner syndrome?
Cocaine eye drops
Stops NorAd re-uptake at the NMJ
Normal eye dilates, in Horner syndrome nerves aren’t releasing NorAd, re-uptake makes no difference
Adrenaline eye drops
Dilates pupil in Horner syndrome but not in normal pupil
What is a Holmes-Adie pupil?
Dilated, sluggish to react to light, responsive to accommodation, slow to dilate after constriction
Absent ankle and knee reflexes are present in Holmes-Adie syndrome
What causes Argyll-Robertson pupil?
Specific to neurosyphilis
Damage to post-ganglionic parasympathetic fibres
AKA prostitues pupil
What characterises an Argyll-Robertson pupil?
Constricted pupil that accommodates to a near object but does not react to light
Often irregulalry shaped
