The condition resolves and the pupil returns to normal size and function without treatment. In one study, the median duration of the episodes was 12 hours (some lasted much longer) and the median frequency was two to three episodes per month. Young women who are prone to migraine appear to have the highest risk of benign episodic unilateral mydriasis. This is an unusual but harmless condition where a person experiences sporadic episodes of one pupil suddenly becoming dilated, often accompanied by blurry vision, headache and eye pain. SEE RELATED: Eye dilation FAQs Benign episodic unilateral mydriasis This slows your eyes' ability to react to light. However, the substances themselves do not cause your pupils to dilate.Ī number of illegal drugs, however, do directly cause dilated pupils. This effect can last two hours or longer after drug ingestion. Research has shown that alcohol and marijuana - separately or in combination - can reduce your eyes' ability to recover from exposure to a bright light source (such as oncoming headlights at night) and adapt to changing light conditions. This is why you see physicians checking an athlete's pupils with a penlight following head trauma sustained during sporting events, or when a patient arrives at a hospital emergency department with other possible stroke symptoms. Brain injury or diseaseĪ head injury, stroke or brain tumor can affect how your pupils react to light and cause dilated pupils. Sometimes, this sort of injury can occur during an eye surgery, such as a complicated cataract surgery or a corneal transplant. The following prescription and non-prescription medicines can cause your pupils to dilate and affect their ability to react to light:īotox and other medications containing botulinum toxinĪtropine (used for myopia control and other medical purposes)Ī serious, penetrating eye injury can damage your iris and cause the pupil to become dilated and irregular in shape. The most common dilated pupil causes include: Medications If one pupil is noticeably larger than the other, you may have something called anisocoria. Your pupils should also dilate symmetrically. However, if your eyes are fully dilated even in a bright environment or if your eyes don't seem to be dilating as they should, it's time to get your eyes checked. It's normal for your pupils to dilate more the darker your surroundings. Submitted comments are subject to editing and editor review prior to posting.If you've noticed your eyes are unusually dilated (larger) or one eye is dilated more than the other, call an eye doctor!.Read any comments already posted on the article prior to submission. Submit only on articles published within 6 months of issue date.(Exception: original author replies can include all original authors of the article) Submissions should not have more than 5 authors.Reference 1 must be the article on which you are commenting. Submissions must be You (and co-authors) do not need to fill out forms or check disclosures as author forms are still valid If you are responding to a comment that was written about an article you originally authored:

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Constricted pupil size