Pupil abnormalities

Question 0

Pupil constriction is controlled by

Answer 0

Sphincter pupillae - constriction (miosis) is controlled by parasympathetic input from the 3rd nerve after it synapses at the cillary ganglion - neurotransmitter is Ach

Question 1

Anisocoria

Answer 1

Difference in the size of the pupils - determined by the balance of the sphincter and dilator muscles
Up to 0.5mm is considered physiological
Physiological anisocoria is the same at all light levels, pupil size difference which varies with light is sinister

Question 2

Miosis

Answer 2

Constriction of the pupil

Question 3

Pupillary dilation is controlled by

Answer 3

Dilator pupillae - controlled by the sympathetic system to dilate the pupil (mydrasis)

Question 4

Mydrasis

Answer 4

Dilation of the pupil

Question 5

How is mydrasis controlled?

Answer 5

A 3 neurone arc -

(1) hypothalamus–>cillo-spinal centre in ‘budge centre’ (C8-T2)
(2) preganglionic fibre from the cord to the sup. cervical ganglion
(3) postganlionic fibre runs along the int. carotid to the short post. Cillary nerves to the dilator muscle

Question 6

How is miosis controlled?

Answer 6

The pupillary light reflex is a 4 neurone arc -
(1) retina to the pretectal nucleus –> (2) pretectal to the Edinger-Westphal nucleus –> (3) EW to the cillary ganglion via 3rd nerve–> (4) cillary nerve from ganglion to sphincter pupillae muscle

Question 7

Causes of pathological anisocoria

Answer 7

Large pupil (in bright conditions) - tonic Holmes-adie pupil, 3rd nerve palsy, eye drops, trauma, iris rubeosis or physiological

Small pupil (in dark conditions) - Horner’s syndrome, eye drops (pilocarpine), uveitis/posterior synechiae or physiological

Question 8

Tonic pupil

Answer 8

A fixed dilated pupil where there is reduced light response, leading to a dilated pupil which can be overcome by accommodation
- A large pupil when looking at distance, normal when looking close
Can be due to autonomic neuropathy (bilateral) or Holmes-adie

Question 9

Holmes-adie syndrome

Answer 9

A benign idiopathic syndrome caused by damage, possibly due to infection of postganglionic parasympathetic fibres
It presents with abnormally dilated pupil with loss of light response, loss of deep tendon reflexes and abnormalities in sweating -> can also have photophobia and reading difficulties

Question 10

Iris rubeosis

Answer 10

Neovascularisation of the iris
Due to proliferative retinopathy and can cause glaucoma
Visible new blood vessels on the surface of the iris

Question 11

Uveitis or posterior synechiae causing small pupils

Answer 11

Idiopathic intraocular inflammation that can cause adhesions between the pupil margin and the lens
This can cause a pupil which is ‘stuck down’ and so cannot dilate

Question 12

Horner’s syndrome

Answer 12

Disruption of the sympathetic supply to the eye
Triad of -
(1) partial ptosis of the upper eyelid
(2) pupillary constriction
(3) Anhydrosis (lack of sweating) on that side of the face

Question 13

Ptosis

Answer 13

Drooping of the upper eyelid
Weakness or palsy of the levator muscle
Can be bilateral or unilateral, congenital or acquired.
Can cause a visual field defect if covering the eyelids

Question 14

Causes of ptosis

Answer 14

Congenital - levator dystrophy or horner’s
Trauma or mechanical
3rd nerve palsy or myasthenia gravis
Levator disinsertion (aponeurotic ptosis, age or trauma)
Chronic progressive external ophthalmoplegia (CPEO)

Question 15

Myasthenia gravis ptosis

Answer 15

A variable, fatiguible ptosis which is worse with effort or at the end of the day

Question 16

Chronic progressive external ophthalmoplegia (CPEO)

Answer 16

Most commonly a symptom of mitochondrial myopathy
Characterised by a slowly progressive inability to move the eye and the eyebrows
Usually a bilateral ptosis