Pupil disorders

Question 1

Define Mydriasis and its physiology.

Answer 1

• Dilated pupil
• Circular muscles in iris – cause pupil constriction. Stimulated by parasymp NS along oculomotor nerve using Ach.

Question 2

Causes of mydriasis.

Answer 2

• Third nerve palsy
• Holmes-Adie syndrome
• Raised intracranial pressure
• Congenital
• Trauma
• Stimulants such as cocaine
• Anticholinergics

Question 3

Define miosis and its physiology.

Answer 3

Constricted pupil.

• Dilation muscles extend radially (outwards from center) through iris. Stimulated by symp NS using adrenaline.

Question 4

Causes of miosis.

Answer 4

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

Question 5

Define 3rd nerve palsy.

Answer 5

• Lack of function (palsy) of CN III = Oculomotor nerve.

Question 6

Causes of 3rd nerve palsy.

Answer 6

• 3rd N palsy which spares pupil (parasymp fibres are spared) caused:
  o Diabetes
  o HTN
  o Ischemia
• Full 3rd nerve palsy = compression of nerve (aka surgical third) causes:
  o Tumor
  o Trauma
  o Raised ICP
  o Oculomotor nerve travels through cavernous sinus and close to post comm A – so cavernous sinus thrombosis or PSA aneurysm can compress nerve and cause palsy.
  o Idiopathic

Question 7

How does 3rd nerve palsy present? Explain why these symp occur.

Answer 7

ptosis, dilated non reactive pupil and divergent strabismus (down and out position).

• Oculomotor nerve supplies all extraocular muscles except lateral rectus and sup oblique.
• Therefore when extraocular muscles are not receiving signals from oculomotor N – eyes move outwards and downwards due to effect of lateral rectus and sup oblique working without resistance.
• Oculomotor nerve also supplies levator palpebrae superioris – lifts up upper eyelid – therefore in third nerve palsy – ptosis.
• Oculomotor nerve also has parasymp fibers that innervate sphincter muscles of iris – therefore get dilated fixed pupil.
• Double vision

Question 8

How is third nerve palsy diagnosed?

Answer 8

• neuro exam.
• CT/ MRI brian to find cause.

Question 9

How is 3rd nerve palsy Mx?

Answer 9

Mx cause.

Question 10

Define Horner’ syndrome

Answer 10

• Damage to symp NS supplying face (one side).

Question 11

Pathophysiology of horner’s syndrome?

Answer 11

damage to oculosympathetic pathway

o Damage to 1st order neuron = lesion above T1 – stroke, tumors, syringomyelia (cyst/ cavity in spinal cord).
o Damage to 2nd order neuron – Pancoast tumor
o 3rd order neuron – dissection of int carotid A

Question 12

How can we locate where damage in Horner’s is given the symp?

Answer 12

determined by anhydrosis.
- Central lesion = 1st order lesions = cause anhidrosis of arm, trunk and face,
o Pre ganglionic lesions = 2nd order lesions – anhidrosis of face
o Post ganglionic lesions = 3rd order lesions – DON’T cause anhidrosis.

Question 13

RF for Horner’s syn?

Answer 13

• Birth trauma (neck trauma at birth).
• Congenital Horner syn – associated w. heterochromia

Question 14

define heterochromia.

Answer 14

diff colour eyes.

Question 15

How does Horner syn present

Answer 15

ipsilateral side as damage.

SPAM (symp NS, ptosis, anhydrosis and miosis).

enophthalmos

Question 16

How are light and accommodation reflexes affected in horner’s?

Answer 16

not affected - stay normal.

Question 17

how is Horner’s syn diagnosed?

Answer 17

• Eye drop test that contains cocaine or apraclonidine.
• CT/ MRI for underlying cause – dissection, malignancies etc.

Question 18

Why is cocaine and apraclonidine used to diagnose horners?

Answer 18

o Cocaine blocks reuptake of NA (symp neurotransmitter) – therefore NA will build up and cause pupil to dilate.
o If there is a block to symp innervation – there will be no NA – therefore no pupil dilation.
o Apraclonidine is a weak form of NA. normally apraclonidine is too weak to cause dilation, but when there is a block of symp innervation the pupil dilatory muscles becomes so starved of innervation that it causes eye to dilate.

Question 19

Mx of horners syndrome?

Answer 19

• Mx cause.
• Surgery for syringomyelia, tumors, carotid A dissection.

Question 20

Define holme Adie.

Answer 20

• Unilateral dilated pupil (benign and dilation starts at early stages – pupil gets smaller over time).
• Pupil reacts slowly to light BUT quickly to accommodation = light-near dissociation.

Question 21

Pathophysiology of holme Adie.

Answer 21

• Damage to post ganglionic parasymp fibres by viral or bacterial infection, e.g HZV.

Question 22

RF for holme adie?

Answer 22

• Young women (3-40 yrs)

Question 23

Presentation of holme adie?

Answer 23

• Small pupil – will get smaller over months to yrs.
• Light-near dissociation.

Question 24

What is holme adie syn?

Answer 24

• Holmes Adie Syndrome = Holmes Adie pupil w/ absent ankle and knee reflexes.

Question 25

Mx of holme adie

Answer 25

• Refer children < 1 yrs.
• Corrective glasses.