Pupil Disorders

Question 1

Pupil constriction

Answer 1

• Circular muscles in the iris cause pupil constriction.
• Stimulated by the parasympathetic NS using acetylcholine as a neurotransmitter.
• 3rd cranial nerve.

Question 2

Pupil dilation

Answer 2

• Dilator muscles arranged like spokes from inside to outside of iris.
• Stimulated by sympathetic NS using adrenaline as a neurotransmitter.

Question 3

Abnormnal pupil shape

Answer 3

• Trauma to sphincter muscles (i.e. surgery)
• Anterior uveitis (can cause adhesions)
• AACG (can cause ischaemic damage usually vertical oval shape)
• Rubeosis iridis (neovascularisation of the iris)
• Coloboma (congenital malformation can cause a hole in the iris leading to irregular shape)
• Tadpole pupil (spasm in a segment of the iris, usually temporary and associated with migraines)

Question 4

Causes of mydriasis (dilated pupil)

Answer 4

• 3rd nerve palsy
• Holmes-Adie syndrome
• Raised ICP
• Congenital
• Trauma
• Stimulants (i.e. cocaine)
• Anticholinergics

Question 5

Causes of miosis (constricted pupil)

Answer 5

• Horners syndrome
• Cluster headaches
• Argyll-Robertson pupil (in neurosyphilis)
• Opiates
• Nicotine
• Pilocarpine

Question 6

Third nerve palsy

Answer 6

• Ptosis (drooping upper eyelid)
• Dilated non-reactive pupil
• Divergent strabismus (down and out)
• Causes with sparing of the pupil include:
  
  • DM
  • HTN
  • Ischaemia
• Causes of full third nerve palsy or ‘surgical’ palsy include:
  
  • Idiopathic
  • Tumour
  • Trauma
  • Cavernous sinus thrombosis
  • Posterior communicating artery aneurysm
  • Raised ICP

Question 7

Horner syndrome

Answer 7

• Triad of:
  
  • Ptosis
  • Miosis
  • Anhidrosis (loss of sweating)
• May also have exopthalmos
• Caused by damage to the SNS supplying the face
  
  • Causes remember as the 4Ss, 4Ts and 4Cs:
    
    • S for Sentral lesions:
      
      • Stroke
      • Multiple Sclerosis
      • Swelling (tumours)
      • Syringomyelia (cyst in the spinal cord)
    • T for torso (pre-ganglionic) lesions:
      
      • Tumour (Pancoast tumour)
      • Trauma
      • Thyroidectomy
      • Top rib (cervical rib)
    • C for cervical (post-ganglionic)
      
      • Carotid aneurysm
      • Carotid artery dissection
      • Cavernous sinus thrombosis
      • Cluster headache

Question 8

Holmes Adie Pupil

Answer 8

• Unilateral dilated pupil that is sluggish to react to light with slow dilation of the pupil following constriction.
• Over time the pupil will get smaller as a result of damage to the post-ganglionic parasympathetic fibres.
• In Holmes Aide syndrome patients will also have absent knee and ankle reflexes.

Question 9

Argyll-Robertson Pupil

Answer 9

• Specific finding in neurosyphilis.
• Constricted pupil that accomodates when focusing on a near object but does not react to light.
• Often irregularly shaped.
• Often called ‘prostitutes pupil’ as it ‘accommodates but does not react’