Dilated pupils or mydriasis

Dilated pupils or mydriasis

01 September 2022

The condition of dilated pupils - or mydriasis - occurs when the black center of the eyes is larger than normal. It can be caused by dilating drops from an eye exam, side effects of medications or traumatic injury.

Pupils dilate naturally due to changes in light and emotional events, but unusual pupil dilation may be due to a medical condition.

Pupils change size to control the amount of light entering the eye. The colored part of the eye (the iris) controls the size of the pupil by small muscles. Depending on the amount of ambient light, the pupils become smaller or larger to regulate the amount of light entering the eye. These changes are called direct responses. The pupils also shrink when the eye focuses on a nearby object. This is called an accommodative response. If the pupil does not shrink in bright light or dilate in the dark, the pupil is not functioning normally.

Often, dilated pupils cause symptoms depending on how light reaches the eye. These include:

  • Blurred vision
  • Headache
  • Sensitivity to light

If you have received dilating drops from an ophthalmologist, your eyes may be dilated for 4 to 24 hours. The duration will depend on the type of drop used and how your body responds to it.

If pupil dilation is the side effect of a medication, the duration may vary depending on the type and dose taken.

When pupil dilation is a reaction to an emotional factor (adrenaline, attraction, stress) it may have a shorter duration, and the pupil may return to normal size in as little as two to three minutes.

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