pupils Flashcards
bilateral smaller than average pupils causes:
opioid narcotic ingestion
increasing age
chronic tonic pupils (initially large but “shrink” over time)
parasympathomimetic agents (such as pilocarpine)
sleep
PONTINE HEMORRHAGES
dilated pupil
CN 3 palsy virtually never presents as an isolated dilated pupil. (check motility, alignment with alternate cover testing or Maddox rod, and ptosis)
uncal herniation 2/2 CN 3 palsy always have AMS
MRA and CTA used to R/O pupil involving CN 3 palsy but they are not indicated in this case.
DDx
tonic pupil (aka Adies pupil)
medication induced mydriasis.
USE: Dilute pilocarpine testing with 0.1% or 0.125% pilocarpine
1) Constriction to dilute pilocarpine = Dx of tonic pupil.
usually applied in both eyes so the contralateral eye serves as a control
2) if no appreciable response to dilute pilocarpine then pilocarpine 1% can be placed in both eyes; if the problem eye fails to constrict then the cause of mydriasis is medication.
If the results of drop testing are inconclusive then the safest option is to have the patient return the next day for repeat evaluation and possible repeat drop testing. In those super rare cases of CN 3 palsy from an aneurysm presenting with isolated pupillary mydriasis, other signs/findings of CN3 palsy will generally appear within several days.
bilateral, larger than average pupils causes
young age seizures arousal (fight or flight response) sympathomimetic medications anoxic brain injury (possibly due to midbrain ischemia).
Pupillary light near dissociation
DDx? Adies tonic pupil Dorsal midbrain syndrome (Parinaud) Syphilis (Argyll Robertson) PRP CN 3 aberrant regeneration Loss of bilateral afferent visual inputs
When the most pronounced pupillary constriction to light is less than the most pronounced pupillary constriction upon near gaze.
Any disease process causing optic neuropathy OU can result in pupillary light near dissociation
(ex: Dorsal midbrain syndrome, PION)
MCC:
Adies tonic pupil* (DDx: Neuro-syphilis)
dorsal midbrain syndrome (with at least one of its classic other features) = 2/2 disruption of pupillary light input to the Edinger-Westphal in the dorsal midbrain 2/2 compression
Argyll-Robertson pupils (small not large pupils with some risk factor on history for syphilis), (DDx: Neuro-syphilis)
APD
MCC = bilateral loss of afferent input from the retina / optic nerves to the pupillary light reflex.
Near response reflex (convergence, miosis, and accommodation) does not rely on afferent input from photoreceptors to cause pupillary constriction, therefore patients with vision loss from severe retina or optic nerve disease will exhibit limited pupillary response to light but retain pupillary constriction with near response.
*2/2 aberrant regeneration of ciliary body parasympathetic input responsible for accommodation. Following disruption of post-synaptic parasympathetics from the ciliary ganglion, accommodative parasympathetics regenerate and aberrantly innervate the pupillary constrictor muscle causing a relative increase in constriction with near response as opposed to light response.
An NLP patient can have light near dissociation. Just ask the patient to imagine looking at an object close to them.
Causes of ipsi/L Horner’s
Anisocoria greater in DARK (due to impaired sympathethic input to side of lesion)
DDx: carotid dissection (3rd order) lung cancer Wallenberg syndrome (PICA stroke) cluster headaches.
Horner’s testing - apraclonidine
Anisocoria greater in dark. REVERSAL of anisocoria with apraclonidine.
Apraclonidine 1% (must give OU)
Alpha adrenergic receptor agonist ACTS MORE ON ALPHA 2 receptors (than alpha 1 receptors). @ ~ 36 hrs, upregulation of alpha-1 receptors 2/2 synaptic denervation.
Normal: mild constriction
Horner: dilates more
Normal pupil response to iopidine - mild constriction 2/2 action on alpha2 receptors (decreased norepi)
Horner pupil - upregulated alpha1 receptors –> dilation
Causes of ipsi/L Horner’s
Anisocoria greater in DARK (2/2 impaired sympathethic input to side of lesion)
nml light reflex & accommodation
ptosis w/nml LF
congenital - iris heterochromia (prblm eye = lighter unlike sturge-weber) 2/2 tumor, head trauma (forceps), brachial plexus injury
Horner’s testing - cocaine 10%
Cocaine 10%: Blocks NE reuptake
at presynaptic cleft… therefore more NorEpi stimulates the pupillary dilator muscle
Normal pupil - DILATES
Horner pupil - poor (or none) dilation
2/2 decreased sympathetic tone (so no change with cocaine 2/2 already low NorEpi in synaptic cleft)
Physiologic anisocoria - both pupils dilate nearly equally leading to
Midbrain corectopia
rare but usually 2/2 diffuse damage to the midbrain which is thought to cause selective inhibition of portions of pupillomotor fibers from the Edinger-Westphal nucleus.
Most cases in the literature have been bilateral and the degree of correctopia may fluctuate. One case showed 5-15 minute cycles of correctopia followed by resolution.
Migraine - pupils
associated “tadpole pupils” is a benign disorder that typically occurs in one eye and includes a sectoral dilation or spasm of the pupil lasting a few minutes. The pupillary events may or may not be associated with a migraine headache but patients with “tadpole pupils” often have a history of migraine headache disorder.
Horner’s testing - hydroxyamphetamine
Hydroxyamphetimine 1%
Releases NE
Normal, 1st, or 2nd-order (central/preganglionic): dilates
3rd-order (postganglionic lesion): no dilation
Tells you that if failure to dilate = 3rd order lesion
RELEASES NorEpi
-can’t perform cocaine and hydroxyamphetamine test in same day
reverse APD
Dilation of one eye (for whatever reason: dilating drops, prior trauma, Adies pupil, CN 3 palsy, etc). does not prevent the accurate assessment of a relative afferent pupillary defect (RAPD).
If one eye is dilated, simply hold a dim indirect light source to the side of the undilated eye (in this case the left eye) and perform the swinging flashlight test. If the undilated eye has a RAPD then it will dilate as expected when the flashlight is swung over from the dilated eye. If the dilated eye has a RAPD, the undilated eye will dilate when the flashlight is swung from the undilated eye to the dilated eye.
Some refer to this as checking for a RAPD “by reverse” but others object to the use of this terminology calling it a misnomer. Misnomer or not, most ophthalmologists understand what is meant by assessing a RAPD “by reverse.”
Adie’s tonic pupil
Sluggish, segmental, vermiliform pupil
Light-near dissociation
Female (70%); 20s-50s
Supersensitive to pilocarpine 0.1-.125% (wait 30 min-1 hr): normal pupil and pupil involving 3rd nerve palsy will both constrict to full strength pilocarpine 1% while a pharmacologically dilated pupil will not.
Tonic pupils = denervation hypersensitivity. Injury to the postganglionic parasympathetic pathway
delayed re-dilation following near-gaze.
-some patient have loss of accommodation. Most patients recover accommodation over time while the tonic pupil is often more longstanding.
-Over many years, tonic pupils often “shrink” and may eventually become more miotic than the normal contralateral eye. The risk of contralateral tonic pupil development is ~2% per year in these patients.
Holmes-Adie syndrome?
Adie’s tonic pupil
Diminished deep tendon reflexes
Orthostatic hypotension
APD of optic tract
Optic tract lesions = CONTRALATERAL homonymous hemianopia (often incongruous) and a CONTRALATERAL APD.
APD = contralateral to the lesion b/c each tract CONTAINS MORE CROSSED THAN UNCROSSED pupillary fibers (recall there is an asymmetric decussation of all axons at the chiasm). Therefore, a lesion of the optic tract will cause more damage to fibers crossing from the contralateral eye than uncrossed fibers from the ipsilateral eye.
Anisocoria
NEVER due to afferent lesion.
