Pupil Disorders - Week 4 Flashcards
What type of pupil defect affects the afferent pathway?
RAPD
Does anisocoria result from an afferent or efferent pathway innervational problem?
Efferent
What is the difference between afferent and efferent pathway?
Afferent: eye to CNS
Efferent: CNS to eye via ANS (autonomic nervous system)
Describe the parasympathetic pathway for iris innervation
EW nucleus – cil. ganglion – short cil. nerve – sphincter pupillae constrict
What neurotransmitter is used for the parasympathetic iris innervation pathway? And what receptors are used?
ACh. Muscarinic or nicotinic receptors
Describe the sympathetic pathway for iris innervation
Midbrain – piggyback on long cil. nerve – exit at T1 spino-centre (pre-ganglionic fibres) – sup. cerv. gang. (post-ganglionic fibres) – follow carotid – through carvernous sinus – dilator muscle
What neurotransmitter and receptors does the sympathetic iris innnervation pathway use?
ACh. Adregnergic or nicotinic.
Where does the pathology occur in RAPD/Marcus-Gunn pupil?
Before the chiasm
What type of pathology could occur to cause RAPD?
- large retinal detachment
- CRAO or CRVO (central retinal artery/vein occlusion)
- O.N ischaemia, asymetric glaucoma
- Optic neuritis, optic nerve compression
Do any of the following result in RAPD?
- cataract
- vitreous haemmorhage
- amblyopia
NO. (though amblyopia may cause very mild RAPD)
Is anisocoria a feature of RAPD?
No. (though that doesn’t mean you can’t have both)
During the swinging light test, how do complete RAPD patients react? (in general)
normal side: regular small relaxation after initial constriction
affected side: both pupils dilate
How does flash luminance effect constriction and escape?
Brigher luminance: more constriction, less relative escape
Dimmer: less constriction, more relative escape
Note: when flashing a light on diseased RAPD eyes, it’s as if less light was delivered to them. because they have less constriction and more relative escape
What do you use to record video pupillometry?
infrared video camera
How does the escape and constriction compare for mild vs severe RAPD patients?
Mild: some constriction and early escape
Severe: No constriction
How do you grade RAPD? Name and describe the grades
No RAPD: pupils constrict and show equal physiological escape
Grade 1+: when light shone onto affected eye, escape apparent @ 3 seconds only
Grade 2+: escape apparent at 2 seconds
Grade 3+: escape apparent at 1 second
Grade 4+: Immediate dilation
Does an afferent defect ever give anisocoria?
No. Never
How many interneurones are there?
2 CNS, 1 peripheral
What does anisocoria in the dark vs light indicate?
More anisocoria in dark: sympathetic (because dilator is weak)
More anisocoria in light: parasympathetic problem
Describe the pupil light reflex in Horner’s syndrome
Anisocoria with dilation lag (i.e. greater anisocoria in dark)
How does Horner’s syndrome affect the following: lids, sweat, IOP, conjunctiva, accommodation, iris
- lid ptosis (apparent enophthalmos)
- facial anhydrosis (lack of sweating)
- IOP reduced on affected side (1-2mm Hg)
- conjunctival flash
- increased accommodation (1D)
iris heterochromia (in congenital/ long standing)
Why does congenital horner’s present with iris heterochromia?
Because sympathetic innervation is needed to develop iris pigmentation and horner’s is an efferent sympathetic problem
Name the 2 causes of congenital horner’s
- brachial plexus trauma
- forceps delivery at birth
How can you assess congenital horner’s?
Family album test (to see change from youth)
for parasympathetic dysfunction, how does a mid-brain lesion vs peripheral lesion affect light and near response?
Mid-brain lesion: poor light response, normal near
Peripheral lesion: both responses poor
What type of light and near response might Percy Grainger’s Mum be likely to present with?
Poor/No light, but good (or brisk) near response
Because she has syphilis, which can cause a mid-brain lesion
List 2 examples of mid-brain lesion pupil problems
- Parinaud’s syndrome (large pupil)
- Argyll Robertson pupil (small pupil)
Describe parinaud’s syndrome: pupil size, gaze, what type of lesion
Large pupil, nystagmus on attempted upgaze, posterior brain stem lesion (still midbrain)
What is the effect of the posterior brain stem lesion? Possible cause of lesion?
- reduced pupil input gives dilated state
- pineal tumour
Describe argyll robertson pupil
Pupils: irregular and miotic (small)
- total absence of light reaction
- brisk near response
What type of lesion causes argyll robertson?
supra nuclear (EW) lesion in descending pathways
Can syphillis cause argyll robertson pupil?
yes
What type of issue would no light response but with near response indicate?
Mid-brain problem
Which type of lesion is a greater cause for concern? Mid-brain or Peripheral
Mid-brain lesion
What type of lesion does Adies Tonic Pupil have, and what does this mean for the light and near response?
Peripheral lesion. Therefore affected eye has no light or near response (still get consensual in other eye though)
What proportion of central ANS defects are sinister?
60%
What proportion of peripheral ANS defects are benign?
80% benign
How does an abnormal peripheral neuron affect neurotransmitter release
reduced basal rate of neurotransmitter. leads to up-regulation in post0synaptic receptors
What type of drug is horner’s supersensitive to? What about Adies?
Horners: adrenergic drugs (2.5% PE)
Adies: cholinergic drugs (1% pilocarpine)
What type of sympathetic drugs can you use to confirm if there’s a problem with sympathetic receptors?
- phenylephrine 2.5% (diluted to 0.1%)
- apracholonidine 0.5%
What type of parasympathetic drugs can you use to confirm if there’s a problem with parasympathetic receptors?
- pilocarpine 1% (0.125%)
