12/6/2023 0 Comments Pupils different sizes![]() Classic clinical findings are unilateral miosis, ptosis, and anhydrosis, which may be present in any combination and also be incomplete and difficult to ascertain. Horner syndrome (HS) involves an abnormally small pupil. If non-dilute pilocarpine fails to constrict the pupil, then the pupil is pharmacologically dilated. This previously was thought to help differentiate this form of mydriasis from TNP, but newer results cast some questions on this. Dilute pilocarpine will cause constriction in a dilated pupil of greater than two weeks due to denervation of the neuromuscular junction. ![]() The muscarinic agent pilocarpine, both dilute (0.05-0.15%) and non-dilute (1 to 2%), acts on the neuromuscular junction of the pupillary constrictor to cause miosis. A dilated pupil can be tested pharmacologically. The diagnostic approach first involves a careful ophthalmological examination. Generally, medications taken systemically will not cause anisocoria since both pupils will constrict or dilate but can cause anisocoria if the medication gets into only one eye. Small pupils may be caused by opiates, clonidine, organophosphates, pilocarpine, and prostaglandins. Dilating agents are nasal vasoconstrictors, scopolamine patches, glycopyrrolate deodorants, and various herbals, such as Jimson weed. Pharmacologic agents may cause both mydriasis, which is more common, and miosis. There are no cranial nerve palsies in tonic pupil cases. The diagnosis of a tonic pupil is usually clinical. Anatomical abnormalities may exist to cause this entity. The tonic pupil is often benign but may eventually become miotic. The affected pupil demonstrates a response with poor constriction to light but significantly better to accommodation this is referred to as light near dissociation. The pupil is large and more commonly occurs in young women. Tonic pupil, or Adie pupil, is a well-known cause of anisocoria. TNP is an example of a large, abnormal pupil. Magnetic resonance angiogram (MRA) has a threshold of 3 to 5mm and may indicate other pathologies. Diagnosis is radiological with computed tomogram (CT) or magnetic resonance imaging (MRI). Patients usually experience pain with this entity. The most well-known, life-threatening cause of TNP is a posterior communicating artery aneurysm causing pressure on the third nerve. Isolated pupillary dilation is not classically considered a third nerve palsy however, careful evaluation for subtle ptosis or abnormal extraocular movement is necessary to eliminate a TNP using this criterion. Important etiologies of anisocoria include third nerve palsy, Adie pupil, pharmacologic mydriasis, pharmacologic miosis, traumatic mydriasis, physiologic anisocoria, and Horner syndrome.Ī third nerve palsy (TNP) may spare the pupil or cause it to dilate with no reaction to light or convergence.
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