Inclusion Criteria:  All patients presenting to the emergency room, aged 18 years or over, able to communicate, with hemodynamic and respiratory stability, are eligible.  Exclusion Criteria:  - Refusal to participate in the study; refusal to sign informed consent. Consent impossible to obtain (cognitive disorders, language barrier…). Patient taking immediate-release opioid medication (last dose within the last 12 hours). Patient taking prolonged-release opioid medication (last dose within the last 24 hours). Basic treatment with a dopaminergic D2 antagonist (antipsychotic drugs). Basic treatment with dopamine antagonist antiemetic medication (metoclopramide (T1/2 5-6h), domperidone (T1/2 7-9h), alizapride (T1/2 3h)) within the last 12 hours. Patient taking clonidine (last dose within the last 24 hours). Use of topical ocular drugs modifying pupillary parameters in the last 24 hours. Bilateral eye surgery modifying the possibilities of variation in pupillary diameter bilaterally. Parkinson's or Alzheimer's disease at a dysautonomic stage. Admission to the emergency room for acute ocular pathology. History of diabetes at a dysautonomic stage. History of alcoholism at a dysautonomic stage. History of glaucoma. Pregnant patient with preeclampsia.