Pupil dilation is a normal, healthy response to a variety of possible stimuli. For example, a pupil should dilate and become larger in the dark, but constrict when there’s ample light. However, a number of issues can cause a pupil to remain dilated, even in well-lit areas. Physicians refer to this condition as mydriasis, though some medical experts use mydriasis as a general term for any instance of dilated pupils, even natural ones. Some fields use the term “blown pupil” to refer to mydriatic pupils that result from specific conditions.


1. Benign Episodic Unilateral Mydriasis

Benign episodic unilateral mydriasis is an unusual condition that can cause one pupil to dilate. Individuals with this condition may experience additional symptoms while their pupil is dilated. Headaches are common, as are blurry vision, and light sensitivity. People who frequently experience migraines may also develop benign episode unilateral mydriasis. The condition is often non-serious, though a medical examination may be necessary to ensure there isn’t an underlying condition or injury.

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