Miosis

A pathologic or pharmacologic constriction of the pupillary aperture (diameter ≤2 mm) caused by increased sphincter pupillae activity or reduced pupillary dilator function.

Causes

• Medications and toxins affecting autonomic pupillary control

  • Opioid intoxication

  • Cholinergic or miotic agents

  • Nicotine exposure

  • Clonidine

  • Organophosphate poisoning

• Neurological disorders affecting pupillary pathways

  • Brain trauma

  • Pontine lesions

  • Brainstem injury

  • Intracranial hemorrhage

  • Horner syndrome

  • Neurosyphilis

  • Autonomic nervous system dysfunction

• Inflammatory disorders of the anterior eye segment

  • Iritis

  • Uveitis

• Physiological causes

  • Bright light exposure

  • Near focusing (accommodation reflex)

  • Deep sleep

  • Normal aging-related changes