Mydriasis and Miosis - Differential Diagnosis Framework



Causes of Mydriasis:

Dilated pupils (mydriasis) more than 7mm

 • Unilateral Mydriasis: CN Ill paralysis (PCA Aneurysm), Brainstem herniation (Comatose), Acute angle closure glaucoma, Adie's tonic pupil, Migraine Headache, Traumatic Mydriasis

 • Bilateral Mydriasis: 

    - Medications: Opiate withdrawal, Antipsychotic medications, AntichoIinergic medications, Mirtazapine, MAO inhibitors, Organophosphate inhibitors, Atropine, Antihistamines, Dopamine, Barbituate toxicity

    - Stimulants: MDMA (Ecstacy), TCA, Cocaine, LSD, Psilocybin mushrooms, PCP, Ketamine

    - Dim light response, Serotonin syndrome, Carbon monoxide

    - Fixed: Brain death, Hypothermia



Causes of Miosis:

Constricted pupils less than 2mm

 • Unilateral Miosis: Horner's syndrome, Posterior Synechiae, Pilocarpine, Iris inflammation (iridocyclitis, uveitis)

 • Bilateral Miosis:

    - Bright light response

    - Medications: Opiates, Clonidine, Benzodiazepines, Pilocarpine, Insecticides, Bromides, Valproic acid

    - Others: Anticholinergics, Sympathomimetics, Organophosphates, Nicotine, Heat Stroke

    - Neuro: Pontine hemorrhage, Pontine CVA, Syphilis (Argyll Robertson pupils), DM, SAH



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