Dilated Pupils & Pupil Dilation: Causes & What to Do

Having dilated pupils, or larger-than-normal pupils, can signal a serious head or eye injury. Or it can be a sign of an impending romantic or sexual encounter.

The causes of eye dilation also include medicated eye drops from the eye doctor prior to an eye exam, non-eye-related prescription medications and recreational drug use.

Most cases of dilation are not serious, and the pupils return to normal without treatment. But in some cases, medical intervention is needed.

Pupils are the black spots in the center of the eye, and their function is to allow light to enter. Normal pupil dilation is 2 to 4 millimeters when exposed to bright light and 4 to 8 millimeters in dim light.

Anything beyond 8 millimeters is considered unusual and abnormal pupil dilation. The condition, called mydriasis, is caused by certain medications, eye injuries, brain injuries and sexual arousal.

Causes of Dilated Pupils

The most common causes of dilated pupils are:

• Medications
• Eye injuries
• Recreational drug use
• Brain disease or brain trauma
• Sexual arousal
• Mydriatics

Medications

Some medications can affect a pupil’s ability to dilate or over-dilate. These include:

• Decongestants
• Antihistamines
• Anti-seizure drugs
• Motion sickness drugs
• Tricyclic antidepressants
• Atropine
• Botox

Eye Injuries

Serious penetrative eye injuries can damage the pupil, causing it to dilate irregularly. It is possible that eye can occur during a surgical procedure like a corneal transplant or cataract surgery. 

Recreational Drug Use

Alcohol and drugs like marijuana also affect pupil dilation. These recreational substances affect the pupil’s response to direct light like oncoming headlights.

Other substances that directly affect a pupil’s dilation include LSD, amphetamines, cocaine, psychedelic mushrooms and ecstasy.

Brain Disease or Trauma

A stroke, a brain injury and a brain tumor all affect how pupils dilate. The trauma can impact one eye or both eyes.

This is why when someone is brought to an emergency room with a head injury or severe head trauma, one of the first things the doctors do is check the person’s eyes. They are looking at pupil dilation.

Sexual Arousal

An increase in oxytocin and dopamine will cause pupils to dilate. Dopamine is known as “the feel good” hormone, which the body produces when it feels something pleasurable. Oxytocin is often referred to as “the love hormone” and levels of it increase during physical affection.

Our brains receive a surge of these hormones when we are romantically or sexually attracted to someone. The hormonal boost causes excess dilation.

Mydriatics

Mydriatics are medications that intentionally cause pupil dilation. Eye doctors use mydriatics in their practices to induce dilation so they can look deeper into the eye during exams.

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Treatment: How to Manage Pupil Dilation

Dilated pupils typically return to a normal size on their own without treatment. But severe pupil dilation may require one or more of the following interventions:

• Wearing polarized or photochromic sunglasses to minimize sunlight sensitivity
• Wearing prosthetic contact lenses for a dilated pupil caused by trauma can help improve the pupil’s appearance
• Surgery to repair damage caused by an injury
• Rehabilitation from substance abuse can help reduce pupil size over time
• Avoiding eye-straining work, such as focusing on a computer screen or reading

When pupils are strained, the return to normal dilation is delayed.

Purpose of the Dilated Pupil Exam

A pupil dilation exam purposely increases the size of pupils for the doctor to check the health of the optic nerve and the retina at the back of the eye. Doctors use this crucial exam to detect conditions that may lead to vision loss. 

Such conditions include diabetic retinopathy, age-related macular degeneration and glaucoma. Left untreated, these conditions can lead to vision loss. 

Pupil dilation exams are essential for people who:

• Are experiencing eye problems
• Have had eye problems in the past and require a checkup
• Are genetically predisposed to develop eye conditions 

How Long Dilation Lasts after an Exam

If you have your eye dilated at the eye doctor’s office, you can expect your the pupils to remain dilated for four to six hours after you leave. The pupil’s size should return to normal after that duration.

However, some people may experience dilation for longer than six hours. In fact, some eye drops can cause dilation for up to 24 hours. Your doctor should let you know about this extended period, and you should remind yourself to ask before you leave the office.

If the pupil dilation is tied to drugs or medication, dilation may last for as long as the medication dosage lasts. Similarly, dilation from the taking of recreational drugs should dissipate after the high from the drugs wears off.

Dilation from sexual arousal can wear off in a few minutes.

Pupil dilation caused by emotional factors such as stress, attraction or adrenaline usually returns to normal after a few minutes. 

Side Effects of Dilated Pupils

Common side effects of pupil dilation are as follows:

• Increased sensitivity to light
• Blurry vision
• Trouble focusing on nearby objects
• Eye stinging because of dilation eye drops

In rare cases, a patient may experience an allergic reaction to eye drops in. Less common side effects of pupil dilation include fever, dry mouth, rapid pulse, and swollen and red eyes.

Patients should call a healthcare provider if they notice the following:

• One pupil being larger than the other 
• Headache, dizziness, or confusion
• Sudden pupil dilation not caused by light changes
• Unchanging pupil size when light changes
• Dilation that persists for more than a day

FAQs

What does it mean when your pupils are dilated?

It means that the center of your eye, that is, the dark part, is larger than usual. This happens when there is too little light entering the eye, so the pupils enlarge (dilate) to allow more light in. Pupils also dilate when there is a surge in oxytocin and dopamine hormones. 

Do your pupils dilate when you love someone?

Yes. The love hormones oxytocin and dopamine do affect pupil size. A surge in these chemicals happens when a person is around someone they like or love. The increase in these chemicals causes a slight dilation of the pupils.

References

1. Could Hallucinogens Cause Permanent Pupil Changes in users? A Report from New Zealand. (August 2017). Case Reports in Neurological Medicine.

2. Get a Dilated Eye Exam. (May 2021). National Eye Institute.

3. Lasting bilateral mydriasis after traumatic brain injury may not always be a lost cause. (September 2017). Surgical Neurology International.

4. Why are my pupils so naturally large? (November 2014). American Academy of Ophthalmology.