Miosis refers to the abnormal or excessive constriction (narrowing) of the pupil. The pupil is the black, central opening of the eye that regulates the amount of light entering the retina. In miosis, the pupil becomes smaller than normal, which can occur physiologically (as a normal response to light) or pathologically due to certain medical conditions, medications, or injuries.

Common Causes of Miosis

• Normal Response to Light
  Pupils naturally constrict in bright light to protect the retina from excessive exposure.
• Use of Certain Medications
  Drugs such as opioids, pilocarpine (used in glaucoma treatment), or some antipsychotic medications can cause miosis.
• Neurological Disorders
  Conditions like Horner’s syndrome, brainstem stroke, or cranial nerve III palsy may present with miosis.
• Eye Disorders
  Uveitis (inflammation of the uveal tract) can lead to miosis as part of the inflammatory response.
• Toxic Exposure
  Exposure to certain chemicals or toxins, such as organophosphates (found in some pesticides), can cause marked pupil constriction.

Symptoms Associated With Miosis

Depending on the underlying cause, miosis may be accompanied by:

• Blurred or impaired vision, especially in low-light conditions
• Eye pain or discomfort
• Redness or inflammation of the eye
• Ptosis (drooping of the eyelid) if related to neurological causes
• Headache or facial sweating (in specific syndromes like Horner’s syndrome)

Diagnosis and Treatment

A detailed eye examination by an ophthalmologist or neurologist is essential. The diagnostic process may include:

• Pupil reactivity testing
• Slit-lamp examination
• Neurological assessment
• Imaging studies (MRI, CT scan) if neurological causes are suspected

Treatment depends on identifying and managing the underlying cause. For example:

• Discontinuing or adjusting medications
• Treating infections or inflammatory diseases
• Addressing neurological issues through appropriate medical intervention

Important:
Persistent or sudden-onset miosis without an obvious cause should always be evaluated by a healthcare professional, as it may signal a serious underlying condition.