Pinpoint Pupils (Miosis): Symptoms & Signs

Medically Reviewed on 10/12/2020

Miosis is the medical term for constricted pupils of the eye or pinpoint pupils. Shrinkage of the pupil size is normal in bright light, but when the pupil does not react normally to light levels and stays small, this can be a sign of a medical problem.

Common causes of shrunken pupils include

  • aging,
  • medication side effects, and
  • inflammation within the eye structures.

Miosis is also seen in certain medical conditions, including Horner's syndrome, and may occur with a stroke. Being born without the muscle that controls the pupils or with defects in the pupil muscles is called congenital miosis or microcoria. Depending on the exact cause, miosis can affect one or both pupils.

Other causes of pinpoint pupils (miosis)

  • Aging
  • Aphakis
  • Horner's Syndrome
  • Intracranial Bleeding
  • Iridocyclitis
  • Medication Side Effects
  • Microcoria
  • Neurosyphilis
  • Opioid Addiction
  • Poisoning or Toxins

Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.