Pupil examination Flashcards
What are 7 aspects of pupil examination?
- check lids, iris colour
- ask pt to look at distant target
- measure pupil diameters in ambient bright light
- measure pupil diametesr in ambient dim light
- check direct and consensual pupillary response for each side
- check for RAPD
- ask pt to look at near target
What are 7 stages to the light reflex?
- CN II
- pretectal nucleus
- Edinger-Westphal nuclei (bilateral)
- CN III (inferior)
- Ciliary ganglion
- Short ciliary nerve
- Constriction
What are 6 stages to the near response reflex?
- Visual area 19
- Frontal eye field
- CNIII / Edinger Westphal nuclei
- ciliary ganglion –> short ciliary n –> constrict + accommodate
- (simultaneously) medial rectus –> convergence
What is light-near dissociation?
dorsal midbrain pathology selectively reduces the response to light whilst preserving the response to near
Why is light-near dissociation thought to occur?
fact that near pathway is placed ventral to the more dorsal pretectal nucleus serving the light pathway
What are 8 stages to the sympathetic pathway controlling the pupils?
- Posterior hypothalamus
- T1 (cilispinal centre of budge)
- White rami communicates
- Superior cervical ganglion
- Internal carotid artery
- CNVa (nasociliary branch)
- Long ciliary n.
- Dilation
What is an example of pathology causing an abnormally large pupil?
Adie’s pupil
What is a pharmacological test for abnormally large pupil?
Pilocarpine
How does testing an abnormally large upil with pilocarpine work?
it is a direct muscarinic agonist; normal pupil will constrict in response to 1% pilocarpine. a response to 0.125% indicates denervation hypersensitivity which occurs in an Adie’s pupil
What are 3 steps to the method of the pilocarpine test in Adie’s pupil?
- Administer drop of 0.125% pilocarpine to both eyes
- at 0 and 30 min measure the pupil size when fixing on a distant target in identical dim lighting conditions
- in Adie’s, the affected eye shows a significantly greater response
What is an example of an abnormally small pupil?
Horner’s syndrome
What are 3 pharmacological tests for Horner’s pupil?
- Apraclonidine
- Cocaine
- Hydroxyamfetamine
How does apraclonidine work to test an abnormally small pupil?
has weak alpha-1-agonist activity with little effect on the normal pupil
in Horner’s syndrome the abnormal pupil will dilate in response to apraclonidine, there may be reversal of associated ptosis
How can cocaine be used to test an abnormally small pupil e.g. Horner’s?
inhibits noradrenaline (NorA) reuptake at the neuromuscular junction of the dilator pupillae, so increasing sympathetic tone
in normal sympathetic pathway, cocaine results in idilation; will not dilate in Horner’s
How does hydroxyamfetamine help localise the lesion in Horner’s syndrome?
- stimulates release of preformed noradrenaline
- in first or second order Horner’s, post-ganglionic neurone is intact so pupil will dilate in response to hydroxyamfetamine
- in third order Horner’s, the pupil will not dilate
