Miosis refers to the constriction of the pupil, the black circular opening in the center of the eye. This constriction is controlled by the sphincter pupillae muscle, which is innervated by the parasympathetic nervous system.
Causes of Miosis
Miosis can occur due to various factors, including:
- Normal physiological responses:
- Bright light: The pupils constrict to reduce the amount of light entering the eye.
- Accommodation: When focusing on near objects, the pupils constrict.
- Medications:
- Opioids: These pain relievers can cause miosis.
- Certain eye drops: Some eye drops, like those used to treat glaucoma, can constrict the pupils.
- Medical conditions:
- Horner's syndrome: This neurological condition can cause miosis, along with other symptoms like drooping eyelid and decreased sweating.
- Brain injury: Damage to certain areas of the brain can result in miosis.
- Certain types of poisoning: Exposure to certain toxins can cause miosis.
Significance of Miosis
Miosis can be a sign of a serious medical condition, especially if it occurs suddenly or is accompanied by other symptoms. However, it can also be a normal physiological response. If you experience miosis, it is important to consult a doctor to determine the underlying cause.
Examples of Miosis
- Pinpoint pupils: This is a severe form of miosis where the pupils are extremely small. It can be a sign of opioid overdose.
- Unilateral miosis: Miosis that affects only one eye can be a sign of Horner's syndrome.
