Pupil and Eyelid Disorders Flashcards
What causes pupil constriction?
The parasympathetic fibres which travel with the Oculomotor nerve and innervate the circular muscles/sphincter pupillae
What causes pupil dilation?
Muscles in the eye that are innervated by adrenaline.
What causes abnormal pupil shape?
Trauma to the iris
Cataract surgery, other eye operations
Anterior uveitis
Acute angle closure glaucoma (due to ischaemic damage to the muscles)
Rubeosis iridis - neovascularisation of the iris.
Coloboma - genetic malformation of the eye
Tadpole pupil - spasm in the dilator muscles causing misshapen pupil associated with migraines.
Causes of mydriasis?
mydriasis - dilated pupil
3rd nerve palsy Raised intracranial pressure Trauma Congenital Stimulants Anticholinergic medications
Causes of miosis?
Pupil constriction
Horners Cluster headache Neurosyphillis Opiates Nicotine Pilocarpine eye drops
How does a third nerve palsy present?
Ptosis - drooping eyelid
Mydriasis
Divergent strabismus - down and out position
Why do you get ptosis in a third nerve palsy?
Due to defective innervation of the elevator palpebrae superioris
What is the course of the 3rd nerve through the skull to the eye?
Travels in a straight line through the cavernous sinus
Travels close to the posterior communicating artery
What are the causes of a third nerve palsy?
Can be idiopathic
sparing of the pupil? Microvascular cause as the parasympathetic fibres are spared.
Without sparing of pupil? Compression with a tumour, trauma, cavernous sinus thrombosis, posterior communicating artery aneurysm, raised ICP
What is Horners syndrome?
Triad of ptosis, miosis and anhydrosis.
Enophthalmos is common.
Light and accommodation reflexes are not affected.
What causes Horners syndrome?
Damage to the sympathetic nerves to the eye.
What is the course of the sympathetic trunk?
Starts in the spinal cord at a thoracic level and ascends up the spinal cord (preganglionic nerves) and enter the sympathetic ganglion at the base of the neck.
Exit sympathetic ganglion as postganglionic nerves. Travel to the head alongside the internal carotid artery.
How do you locate the lesion of Horners syndrome?
This can be deducted depending on the location of the anhydrosis.
Central lesions - arm, trunk and face
Preganglionic lesions - face only
Postganglionic lesions - no anhydrosis
What are the causes of Horners syndrome?
The 4 S’s, the 4 T’s and the 4 C’s
Central (S) Stroke multiple Sclerosis Swelling (tumours) Sringomyelia
Torso Tumour (pan coast) Trauma Thyroidectomy Top rib (cervical rib)
Cervical Carotid aneurysm Carotid artery dissection Cavernous sinus thrombosis Cluster headaches
What condition is associated with Horner’s syndrome?
Heterochromia - these patients can be born with Horners syndrome
How do you test for Horner’s syndrome?
Cocaine eyedrops
In patients with no pathology, this will cause dilation of the pupil.
In Horner’s syndrome there will be no pupillary changes
Adrenaline drops will dilate a pupil with Horner’s syndrome but not with a healthy pupil.