Pupil response 2 Flashcards
When do pupils dilate?
In the darkness, low illumination
How is dilation innervated?
sympathetic nervous system branch of autonomic nervous system
Where do all sympathetic fibres originate?
Superior cervical ganglion
What does superior cervical ganglion receive?
Input from cells in the brainstem that synapses to T1
Explain the sympathetic innervation of the orbit?
SCG recieve input from brainstem cells and synapse onto T1
>fribres run from SCG up the neck as the internal carotid nerves to level of cavernus sinus
>break into bundles (plexus), around carotid arteries
>pass through optic foremen
>fibres run along optic nerve to the ciliary ganglion
…
What is marcus gunns test?
Swinging lights test as the eyes are alternatively illuminated
What causes afferent pupil defect?
Optic neuritis
amblyopia
macular disease
retinal detachment
What do efferent pathway pupillary defect result to?
Anisocornia (unequal pupil size)
Where in efferent pathway can the defect be in?
The midbrain EWN
Third nerve
Ciliary ganglion
iris
What is adies syndrome?
Unresponsive tonic pupil due to denervation of the pupil
Where is lesion for argyll robertson pupil ?
Midbrain near EWN
What is argyll robertson pupil ?
pupil unresponsive to light maintains a near response
What is horner’s syndrome?
The pupil of the affected eye is not as dilated as the other eye since the parasympathetic innervation of the dilator is compromised
What happens in horner’s syndrome?
Pupil takes longer and less to dilate as it gets darker
where is the lesion for horners syndrome?
pupil constriction caused by lesion anywhere in the sympathetic pathway leading to the dilator
explain pharmacology of the sphincter?
Blocking the sphincter causes dilation while enhancing its activity results in constriction
- –Pilocarpine - Ach antagonist activating Ach receptors and causing constriction
- –Anti muscarinics will block Ach receptors and result in dilation
- -Anticholinestrase will enhance Ach levels and hence result in sphincter activation and pupil constriction
Explain Pharmacology of the dilator?
Activation of the dilator causes dilation while blocking its effects causes pupil constriction?
>increase the release of NA and hence also causes dilation
>dilator can be relaxed by applying alpha adrenergic blockers causing constriction
>cocaine prevents the reuptake of NA and hence causes dilation
