Miosis
Miosis, also known as pupillary constriction, is the excessive constriction of the pupil of the eye. It is the opposite of mydriasis, which is pupillary dilation. Miosis can be caused by a variety of factors, including medications, medical conditions, and exposure to certain substances.
Causes:
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Medications: Opioids (such as morphine, codeine, and heroin), cholinesterase inhibitors (used to treat glaucoma and Alzheimer's disease), and certain antipsychotics can cause miosis. Pilocarpine is a direct-acting parasympathomimetic that is frequently used to induce miosis, particularly in the treatment of glaucoma.
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Medical Conditions: Horner's syndrome (a disruption of the sympathetic nerve pathway to the eye), cluster headaches, pontine hemorrhage (bleeding in a part of the brainstem), and uveitis (inflammation inside the eye) can all lead to miosis.
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Exposure to Substances: Organophosphates (found in some pesticides and nerve agents) and certain types of mushrooms can cause significant miosis.
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Normal Physiological Response: Bright light exposure will normally cause the pupils to constrict (miosis) to reduce the amount of light entering the eye. This is a natural reflex.
Symptoms:
The primary symptom of miosis is abnormally small pupils, which may be noticeably smaller than normal. Depending on the underlying cause, other symptoms may include:
- Headache
- Eye pain
- Blurred vision
- Sensitivity to light (photophobia)
- Double vision
- Drooping eyelid (ptosis)
- Facial sweating (anhidrosis)
Diagnosis:
Diagnosis typically involves a physical examination by a medical professional, including a thorough examination of the eyes. The doctor will assess pupil size, reactivity to light, and eye movements. A review of the patient's medical history and medication list is also important. Additional testing may be performed to determine the underlying cause of the miosis, such as neurological examinations or blood tests.
Treatment:
Treatment for miosis focuses on addressing the underlying cause. If the miosis is caused by medication, the medication may need to be adjusted or discontinued. If it's caused by a medical condition, treatment will be directed at managing that condition. In some cases, no specific treatment may be necessary, particularly if the miosis is mild and does not cause any other symptoms. Dilating eye drops may be used in some cases to counteract the effects of miosis, but this is typically reserved for specific situations.