Dilated Pupils (Mydriasis)

Dilated pupils (mydriasis) are when the black center of your eyes are larger than normal. The condition may be caused by dilating eye drops from an eye exam, the side effects from a drug/medication or traumatic injury. Pupils naturally dilate due to changes in light and emotional events, but unusual pupil dilation could be the result of a medical condition.

Overview

Illustration of constricted vs. dilated pupils
When you're outside in the sunlight or in a brightly lit room, your pupils constrict (get smaller). When it gets darker, your pupils dilate (get bigger) to let in more light.

What are dilated pupils?

If your pupils are dilated, the black center of your eyes (pupils) are larger than usual. Pupils are typically the same size in both eyes.

Pupils change in size to control how much light enters your eye. The colorful part of your eye (iris) controls the size of your pupil with tiny muscles. In bright light, your pupils will get smaller to prevent light from entering. In the dark, pupils get larger to allow more light in. These changes are called direct responses.

Pupils also shrink when you focused on a close object. This is called an accommodative response. If a pupil does not get smaller in bright light or expand in the dark, the pupil is not functioning normally.

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What is mydriasis?

Mydriasis is when the pupil is dilated and doesn’t respond to light. Another term for mydriasis is “fixed pupil.”

What is a normal size for pupils?

A pupil’s normal size is 2 to 4 millimeters in bright light and 4 to 8 millimeters in dim light (dilated).

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What do dilated pupils look like?

Pupils are dilated when the center black portion of your eyes takes up more space than the colorful portion of your eyes (iris).

Should I be worried about my dilated pupils?

Pupils are supposed to dilate under normal circumstances due to light changes and emotional variables. Most of the time, dilated pupils will go back to normal size on their own. If pupils dilate suddenly, occur after a traumatic injury or cause headaches and confusion, seek medical attention immediately.

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Can one pupil be more dilated than the other?

Yes, when one pupil is more dilated than the other it is called anisocoria. This common condition occurs when both pupils react normally to light but vary in size by more than half a millimeter. Anisocoria affects about 20% of the population.

Possible Causes

What are the most common causes of dilated pupils?

The most common causes of dilated pupils are:

  • An eye exam (eye drops used to examine nerves and retina).
  • A reaction to medication.
  • A brain injury.
  • The use of recreational drugs.
  • Sexual arousal (increased production of oxytocin hormone).
  • Adrenaline.

What recreational drugs cause dilated pupils?

Certain recreational drugs can dilate pupils, including:

  • Cocaine.
  • Ecstasy (MDMA).
  • LSD.
  • Methamphetamines.
  • Psychedelic mushrooms.

What medications cause my pupils to dilate?

Certain over-the-counter and prescription medications can also lead to dilated pupils, including:

What conditions cause dilated pupils?

Some medical conditions or injuries also dilate pupils, including:

  • Adie's pupil (abnormal pupil response to light in one eye).
  • Anisocoria (both pupils are different sizes).
  • Eye injury.
  • Head trauma.
  • Microvascular cranial nerve palsy (blood flow to nerves is blocked).
  • Migraine.
  • Ocular migraine (one eye can experience a sudden array of changes, similar to migraine sufferers without the headache.)

Care and Treatment

Do dilated pupils hurt?

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

  • Blurry vision.
  • Headaches.
  • Light sensitivity.

How are dilated pupils treated?

Most of the time, dilated pupils will return to normal on their own without treatment, especially if they are the result of eye drops. For more serious cases of mydriasis, further treatment is required, including:

  • Wearing sunglasses to reduce sunlight sensitivity (photochromic lenses, polarized lenses).
  • Prosthetic contact lenses (to improve the appearance of eyes as the result of varying pupil size caused by trauma).
  • Surgery (to repair eye damage from injury).
  • Substance abuse rehabilitation.

How long will my pupils be dilated?

If you received dilating eye drops from an ophthalmologist, your eyes could be dilated between four and 24 hours. The length of time is dependent on the type of drop used and how your body responds to it.

If pupil dilation is the side effect of a medication or drug, the duration may vary based on the type of drug and the dosage taken.

Pupil dilation that's a reaction to an emotional factor (adrenaline, attraction, stress) could have a shorter duration, and the pupil could return to normal size in as little as two to three minutes.

When To Call the Doctor

When should I contact my healthcare provider?

Although it is normal for dilation to occur based on changes in light, mydriasis could be a sign of an eye injury or problem within the brain, like a head injury, tumor or stroke. Contact your healthcare provider if you experience any of the following:

  • Dizziness, headache or confusion (signs of a stroke).
  • Sudden pupil dilation that isn’t caused by light change.
  • Pupils don’t change when light changes.
  • One pupil is larger than the other.
  • Dilation persists for long periods of time.

Additional Common Questions

Do your pupils dilate when you love someone?

Pupil dilation can be attributed to an increase in the hormone and neurotransmitter oxytocin, which acts as a chemical messenger during sexual arousal. Oxytocin also plays a role in controlling key aspects of the reproductive system, including sperm transportation and production, childbirth and breastfeeding.

Does anxiety cause dilated pupils?

In some cases, anxiety can cause pupils to dilate as a result of adrenaline. The hormones and chemicals released from the adrenal glands send nerve impulses to organs, leading the body to react in a “fight or flight” mode. Stress can stimulate adrenaline hormones to react, resulting in dilated pupils, increased heart rate, high blood pressure and excessive sweating.

Do your pupils dilate when you lie?

Similar to how your body reacts in a “fight or flight” adrenaline situation, lying can cause hormones and chemicals associated with stress to trigger eye dilation.

A note from Cleveland Clinic

Pupils are supposed to change in size as a reaction to light and normal events in your life. The range of time that pupils dilate varies for each person, but the majority of cases will go back to normal on their own. If you notice your pupils are unusually dilated, reach out to a healthcare professional for treatment.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 01/04/2022.

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