Page 920 - TNFlipTest
P. 920
OP30 Ophthalmology
Pupils
Toronto Notes 2019
CN III palsy with pupillary involvement may be associated with a posterior communicating artery aneurysm
Dilated Pupil (Mydriasis)
Sympathetic Stimulation
• fightorflightresponse
• mydriaticdrugs:epinephrine,dipivefrin(Propine®),phenylephrine
Parasympathetic Understimulation
• cycloplegics/mydriatics:atropine,tropicamide,cyclopentolate(parasympatholytic) • CNIIIpalsy
■ eye deviated down and out with ptosis present
■ etiology includes stroke, neoplasm, aneurysm, acute rise in ICP, DM (may spare pupil), trauma
■ both mydriatics and CN III palsy cause pupil dilation; however, pupils in CN III palsy will constrict
briskly to pilocarpine, while pupils dilated from mydriatics will not
Acute Angle-Closure Glaucoma
• fixed,mid-dilatedpupil
Adie’s Tonic Pupil
• 80%unilateral,F>M
• pupilistonicorreactspoorlytolight(bothdirectandconsensual)butconstrictswithaccommodation • causedbybenignlesioninciliaryganglion;resultsindenervationhypersensitivityofparasympathetically
innervated constrictor muscle
■ dilute (0.125%) solution of pilocarpine will constrict tonic pupil but have no effect on normal pupil
• long-standingAdie’spupilsaresmallerthanunaffectedeye
Trauma
• damagetoirissphincterfrombluntorpenetratingtrauma
• iristransilluminationdefectsmaybeapparentusingophthalmoscopeorslit-lamp
• pupilmaybedilated(traumaticmydriasis)orirregularlyshapedfromtinysphincterruptures
Constricted Pupil (Miosis)
Senile Miosis
• decreasedsympatheticstimulationwithage
Parasympathetic Stimulation
• localorsystemicmedicationssuchas:
■ cholinergic agents: pilocarpine, carbachol
■ cholinesterase inhibitor: phospholine iodide ■ opiates, barbiturates
Horner’s Syndrome
• lesioninsympatheticpathway
• differenceinpupilsizegreaterindimlight,duetodecreasedinnervationofadrenergicstoirisdilator
muscle
• associatedwithptosisandanhydrosisofipsilateralface/neck
• applicationofcocaine4-10%(blocksreuptakeofnorepinephrine)toeyedoesnotresultinpupil
dilation (vs. physiologic anisocoria), therefore confirms diagnosis
• hydroxyamphetamine1%(stimulatesnorepinephrinerelease)willdilatepupilifcentralor
preganglionic lesion, not postganglionic lesion
• postganglioniclesionsresultindenervationhypersensitivity,whichwillcausepupiltodilatewith
0.125% epinephrine, whereas normal pupil will not
• causes:carotidorsubclaviananeurysm,brainsteminfarct,demyelinatingdisease,cervicalor
mediastinal tumour, Pancoast tumour, goitre, cervical lymphadenopathy, surgical sympathectomy, Lyme disease, cervical ribs, tabes dorsalis, cervical vertebral fractures
Iritis
• mioticpupilinitially
• canbecomeirregularlyshapedpupilduetoposteriorsynechiae • laterstagesnon-reactivetolight
Argyll-Robertson Pupil
• bothpupilsirregularand<3mmindiameter,±ptosis
• doesnotrespondtolightstimulation
• respondstoaccommodation(light-neardissociation)
• suggestiveofneurosyphilisorotherconditions(DM,encephalitis,MS,chronicalcoholism,CNS
degenerative diseases)
Other Causes
• opticneuritis,retinallesions
Midbrain
Posterior communicating artery
Normal
Basilar artery
CN III
Post. comm. artery
CN III Parasymp.
Somatic motor
Externally Compressive CN III Lesion
Down and out mydriasis
Post. comm. artery aneurysm
Central Vascular CN III Lesion
Down and out pupil spared
Central infarct
© Andreea Margineanu 2012
Figure 22. CN III lesions with and without mydriasis
Horner’s MAP Miosis Anhydrosis Ptosis