• 12 SECTION Disorders Pupil
Pharmacologically Dilated Pupil
Key Facts
•Unilateral or bilateral mydriatic pupils that do not constrict or constrict poorly to light
•Caused by topical exposure to parasympatholytic or sympathomimetic agent
•If parasympatholytic agent is responsible, there will be impaired accommodation in patients aged <45 years
•Common causes:
•eyedrops • scopolamine patch
•glycopyrrolate cream for hyperhidrosis
•atropinic vegetable substances
•aerosols in ventilator regimens
•Cannot be attributed to orally or parenterally administered medications with parasympatholytic properties
•Always reversible if offending agent is removed
Clinical Findings
•Unilateral or bilateral mydriatic pupils that do not constrict or constrict poorly to light
•Parasympatholytic exposure:
•impaired accommodation in patients aged <45 years
•Sympathomimetic exposure:
•eyelid may be retracted
•conjunctiva may be blanched
•pupil often constricts to bright light
•accommodation is spared
•Pupil may be slightly eccentric, but there is no slit-lamp evidence of segmental palsy, iris atrophy, or synechiae
Ancillary Testing
•Parasympatholytic agent: affected pupil constricts less than fellow pupil to topical pilocarpine 1%
•Sympathomimetic agent: both pupils will constrict normally to topical pilocarpine 1%
Differential Diagnosis
•Recent onset tonic pupil that has not yet developed tonicity, light–near dissociation, or denervation supersensitivity
•Iris dysplasia, inflammation, trauma (including intraocular surgery), prior ischemia from angle closure, carotid occlusive disease
•Mydriatic pupil of third cranial nerve palsy
Treatment
•Eliminate topical exposure to pharmacologic agents with sympathomimetic or parasympathomimetic properties
Prognosis
• Pupil returns to normal as offending agent gradually metabolized
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Fig. 12.5 Pharmacologically dilated right pupil. (A) In dim illumination, right pupil is much larger than left pupil. (B) In bright light, the right pupil does not constrict but the left pupil constricts normally. (C) When a target is viewed at reading distance, the right pupil does not constrict but the left constricts normally. (D) After instillation of 1/10% pilocarpine, neither pupil constricts. (E) After instillation of 1% pilocarpine, the right pupil does not constrict but the left pupil constricts.
Pupil Dilated Pharmacologically
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• 12 SECTION Disorders Pupil
Mydriatic Pupil of Third Cranial Nerve Palsy
Key Facts
•Mydriatic pupil with impaired constriction to light and near target
•Always accompanied by other evidence of third cranial nerve palsy (ptosis or impaired adduction, infraduction, or supraduction; see Third cranial nerve palsy)
•Diplopia usually present
•Suggests compression of third cranial nerve by intracranial lesion such as berry aneurysm
•Isolated mydriasis is never a manifestation of a third cranial nerve palsy
Clinical Findings
•Mydriatic, poorly reactive pupil
•Ipsilateral ptosis or adduction, infraduction, supraduction deficits
•Diplopia usually present
Differential Diagnosis
•Iris trauma
•Pharmacologically dilated pupil
Ancillary Testing
•Brain imaging (MRI or magnetic resonance angiography, CT or CT angiography) may show:
•mass lesion
•aneurysm
•enhancement of third cranial nerve or meninges
Treatment
•Depends on underlying condition
•Prognosis
•Depends on underlying condition
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Fig. 12.6 (A) In darkness, the pupil is dilated in the right eye, which has ptosis and is exodeviated as part of a right third cranial nerve palsy. (B) In brightness, the right pupil does not constrict but the left pupil constricts normally. (C) When a target is viewed at reading distance, the right pupil does not constrict but the left constricts normally. (D) After instillation of 1/10% pilocarpine, neither pupil constricts. (E) After instillation of 1% pilocarpine, both pupils constrict.
Palsy Nerve Cranial Third of Pupil Mydriatic
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