Pupils and ptosis

Question 1

Sphincter pupillae muscle:

Answer 1

Circular smooth muscle at inner ring of pupil.
Innervated via post ganglionic parasympathetic fibers from ciliary ganglion.
Nerves travel with CN3 to ganglion, then with short ciliary fibers of CN6
*supplied via ACh

Question 2

Dilator pupillae muscle:

Answer 2

Single layer of myopeithelium (muscle base, epith. Apex) at pupil base.
Innervated via postganglionic sympathetic fibers from sup. Cervical ganglion.
Nerves travel with long ciliary nerves of CN6
*supplied via noradrenaline

Question 3

Afferent pupil pathway:

Answer 3

Retinal light input > Ganglion cell axions > optic tract > split at chiasm > split before LGN > sup. Colliculus > synapse with olivary pretectal nucleus.
Afferent (retina) / Efferent (midbrain light reflex) signals processed > ipsi/contralateral Edinger Westphal > parasympathetic path.

Question 4

Parasympathetic pupil pathway:

Answer 4

Edinger Westphal > with CN3 (accommodative axons) > cavernous sinus > synapse at ciliary ganglion > with short ciliary via subarachnoid space > iris sphincter > bilateral / equal constriction

Question 4

Sympathetic pupil pathway:

Answer 4

1st neuron: hypothalamus > ciliospinal Centre of bulge and Waller (C8/T2)
2nd: preganglionic fibers pass stellate ganglion (lung apex) > sup. Cervical gang. (jaw)
3rd: postganglionic fibers plexus with carotid > cavernous sinus > SO fiss. With nasociliary of CN5 > long ciliary in suprachoroidal space > dilatory > mydriasis
Also innervate mullers. facial innervation splits before sup. Cervical G.

Question 4

PERRLA examination (first test):

Answer 4

Pupils Equal Round Reactive to Light (direct/consensual) and Accommodative
1. Direct response: light activates ipsilateral EW > ipsilateral constriction
2. Consensual: light activates ipsilateral EW > contralateral EW activation > contraction
Accommodative: Near response triad > visual cortex / pupillomotor Centre in midbrain response

Question 4

RAPD examination (second test):

Answer 4

Swinging flash test for Relative Afferent Pupil Defect.
No RAPD: equal constriction W/O radiation excluding Hippus
Mild: affected pupil constricts and redilates
Moderate: affected pupil does not change, then dilates
Severe: immediate dilation of affected pupil
Lack of consensual response is not RAPD, only examine pupil with light shown on it

Question 5

Horners syndrome symptoms:

Answer 5

Disruption of sympathetic innervation to pupil dilator / mullers / ciliary body / facial sweat glands.
Causes Miosis / partial ptosis (1mm) / anhidrosis (not 3rd order) / accommodative excess / Conj. BV dilation
Congenital cases > Lighter/Darker Brown/Blue eyes

Question 5

Causes of anisocoria:

Answer 5

Efferent pupil pathway dysfunction:
Physiological (EW asymmetric inhibition)
CN3 palsy
Adies tonic
Aberrant regen (CN3p / adies)
Pharmacological
Pupil damage (trauma/Sx)
AAGC

Question 5

Common causes of horners syndrome:

Answer 5

1st : brainstem/spinal disease (vascular/tumor), diabetic neuropathy
2nd: Pancoast tumor, carotid/aortic aneurysm, neck lesion
3rd: carotid aneurysm, cavernous sinus mass, cluster headaches

Question 6

CN3 palsy symptoms:

Answer 6

Mydriasis: Pia BV compression > pupillomotor fiber ischemia
Full ptosis: sup. Levator innervation loss
Down/out turn: Sup/Inf/medial rectus, inf. Oblique innervation loss
Thunderclap headaches

Question 7

Causes of CN3 palsy:

Answer 7

Pupil involving: compressive lesion/aneurysm on pia BV for parasym. fibers
Pupil sparing: DM/HT > main trunk ischemia
* Giant cell arteritis (temple pain) / Pos. communicating artery aneurysm / cavernous fistula common
Myasthenia gravis imitates pupil sparing palsy

Question 7

Adies tonic pupil:

Answer 7

Segmental denervation of post gang. Parasym. > sphincter loss > dilation and wormlike light response
Blur in affected eye with light-near dissociation (accomodative response is healthy following aberrant regen)
Caused by viral infections, usually women

Question 8

Aberrant regen:

Answer 8

Adies: acc. Parasym. From ciliary muscle innervate iris sphincter (2 months) > light/near dissociation > reversal of anisocoria greater in dark
CN3 palsy: accom. Parasym. Regenerate denervated pupils > miosis (anisocoria reversal). Regen can come from oculomotor fibers > miosis on different gaze

Question 8

Common pharmacologic mydriasis/miosis:

Answer 8

Tropicamide: Muscarinic antagonists > Ach receptor block > sphincter paralysis
Phenylephrine: adrenergic 1 agonist
Pilocarpine: muscarinic agonist > Ach receptor upregulation > miosis
Apraclondine: Alpha agonist > dilation (weak a1, strong a2)
Tamulosin: Alpha antagonist > adrenaline receptor block > dilator paralysis

Question 9

Assessing anisocoria greater in light:

Answer 9

Greater in light > parasym. Loss > CN3 palsy / adies
0.1% pilocarpine > great constriction of affect pupil in early adies (<2w) from Ach upregulation
1% pilocarpine > constriction of CN3 palsy
Faliure to constrict > pharmacological/atrophic mydriasis

Question 10

Assessing anisocoria greater in dark:

Answer 10

Greater in dark > sym. Loss > horners/aberrant regen (CN3/adies)
0.5% apreclonidine > pupil dilation of affected eye w/lid raising and constriction of normal pupil. Requires 1w post onset for a1 upregulation
1% hydroxyamphetamine > dilation of affected eye if 1/2 order neuron lesion (release of 3rd neuron noradrenaline)

Question 10

Simple congenital/myopathic ptosis:

Answer 10

Usually unilateral, from fibrotic LPS > raised lid on downgaze + indistinct lid crease
Blepharophimosis syndrome is a type > horizontally short palpebral fissure with no LPS function

Question 10

Types of ptosis:

Answer 10

Myogenic (MG, simple congenital, blepharophimosis)
Neurogenic (CN3, horner, marcus gunn)
Mechanical
Aponeurotic (LPS disinsertion)
Pseudooptosis

Question 11

Myasthenia gravis:

Answer 11

Autoimmune disorder > auto antibodies against Ach receptors of striated muscle > weakness
Causes limb weakness, lack of expression, ptosis +_ diplopia worsening over the day.
Tested via 1minute upgaze, or ice pack for 2m (improves neurotransmission)

Question 11

Chronic progressive external ophthalmoplegia:

Answer 11

Most common mitochondrial myopathy > ATP dysfunction > EOM fatigue
Progressive disease, noted in teenages
Bilateral ptosis > then leteral gaze > down gaze
Rarely causes diplopia as loss is symmetrical

Question 11

Marcus Gunn Jaw winking syndrome:

Answer 11

Synkinetic neurogenic ptosis from CN5(V3 mandibular) anastamosis with CN3 > wink reflex on jaw contraction

Question 12

Aponeurotic ptosis:

Answer 12

Lid disinence/redundancy > high lid crease which remains on down gaze

Question 12

Measuring ptosis:

Answer 12

Margin reflex distance: 4mm from corneal reflex and upper lid
Palpebral fissure: difference between eyes: 2/3/4mm mild/moderate/severe
Levator function: pressure brow, measure upper lid change from downgaze and upgaze (15mm normal)
Upper lid crease: distance between lid margin and crease in downgaze (8mm normal).

Question 13

physiological anisocoria:

Answer 13

1/3 prevelance
longstanding, <1mm discrepancy, stable in light/dark

Question 14

common pharmacologic agents in pupil dilation

Answer 14

Scopolamine patches
nasal vasoconstrictors
antiperspirants
opioids
insecticides

Question 15

clinical assessment of horners

Answer 15

Dilation lag of mitotic pupil in dark (5-15s) > greater anisocoria at 5s, lesser by 15.
W/ no abnormality in near response