Miosis means abnormally small pupils. It can arise from eye conditions, medications, or neurological problems.
Common causes of constricted pupils
Certain drops and systemic drugs cause pupillary constriction. Bright light also naturally makes pupils smaller.
- Pilocarpine and other glaucoma medications
- Opioid painkillers such as morphine
- Normal response to strong light or close focusing
- Horner syndrome can cause one small pupil
Serious neurological causes
Very small pupils with reduced responsiveness can accompany brainstem problems or toxic exposure. Prompt medical review is essential.
- Pontine haemorrhage or stroke
- Organophosphate or nerve-agent poisoning
- Other brain injuries affecting autonomic control
- Emergency assessment is required if miosis appears suddenly with other symptoms
