Pupils Flashcards
Describe the pupil light reflex
Light detection by retina passed to brain via the optic nerve afferent pathway and pupil constriction is mediated by the oculomotor nerve efferent pathway
Sympathetic system is responsible for pupil dilatation via the ciliary nerves
What is the afferent pathway of pupil light reflex?
Retina
Optic nerve
Lateral geniculate body
Midbrain
What is the efferent pathway of pupil light reflex?
Edinger westphal nucleus (midbrain
Occulomotor nerve
Sphincter pupillae
What occurs in an afferent defect? What are the size of the pupils at rest
Optic nerve damage
Pupil won’t respond to light directly but there is a consensual response when light is shined in other eye
Constriction to accommodation still occurs
Pupils same size at rest and consensual reflex is unaffected
What are causes of afferent defects?
Optic neuritis, MS
Optic atrophy
REtinal disease - detachment
What is RAPD
Relative afferent pupillary defect
Marcus Gunn pupil
Swinging light test
On beaming light into normal eye - both pupils constrict, there is direct and consensual response
If on swinging light into the affected eye, the pupil dilates, it is a relative afferent pupillary defect
This is caused by a lesion anterior to the optic chasm - optic nerve or retina
Describe efferent defects? Causes? Which sign first in tumour compression?
3rd nerve mediates eye movement and eyelid retraction
Thus with complete 3rd nerve palsy there is fixed dilated pupil, ptosis and down and out displacement
Causes: Cavernous sinus lesions superior orbital fissure syndrome diabetes Posterior communicating artery aneurysm
Pupils are spared in vascular causes - DM, HTN
Pupillary fibres are peripheral and first affected by compression - tumour, aneurysm
What are causes of mydriasis?
Topical mydriatics - tropicamide, atropine
Sympathomimetic drugs - amphetamines, cocaine
Anticholinergics - tricylcic antidepressants
Third nerve palsy Holmes-adie pupil Phaeochomocytoma Acute glaucoma Coning - uncle herniation
What is tonic (Holmes Adie) pupil?
Lack of parasympathetic innervation results in poor construction to light
Initially unilateral then bilateral
Pupil dilation with delated responses to near vision effort with delayed redaction - once pupil has constricted it remains small for an abnormally long time
Slowly reactive to accommodation but poorly if at all to light
Young woman presnsets with sudden blurring of near vision and dilated pupil with slow responses to accommodation and light.
What does slit lamp show? Diagnosis?
Iris shows spontaneous wormy movements - can be caused by damage to local structures
Holmes- Adie pupil
What is Holmes adie syndrome
Association of holmes adie pupil with absent knee/ankle reflexes and impaired sweating.
What are the features of honer’s syndrome?
Miosis - paralysis of dilator pupillae - no dilation in dark
Partial ptosis - paralysis of superior tarsal muscles
Anhydrosis
Disruption of sympathetic fibres
What indicates congenital Horner’s
Iris heterochromia
- difference in iris colour
How can you determine where the lesion is in Horner’s?
Central lesions show anhydrous of face arms and trunk
Pre-ganglionic lesions - proximal to carotid plexus shows anhydrous of the fact
Post-ganglions lesions - distal to carotid plexus, sudomotor fibres have separated so no anhydrosis
What are causes of central lesions causing Horner’s?
Stroke
Syringomyelia
multiple Sclerosis
