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Can You Get Side Effects From Eye Dilation?

I'm a former pharmacy technician and certified medical office assistant. I'm also a health nerd/ hypochondriac and knowledge eases my fears.


Why Are Eyes Dilated for Eye Exams?

If you are wondering whether you can get side effects from eye dilation, you may likely be worried about your upcoming eye exam.

To better understand what happens to your eye upon dilation, it helps to better understand the purpose of the procedure and how it all works.

Firstly, why are eyes dilated for eye exams?

By obtaining a pupil diameter of about 6mm, the eye doctor has the opportunity for a more detailed examination. When the pupil is dilated, courtesy of special eye drops, your eye doctor can better visualize the inner eye structures, such as the macula, retina, and optic nerve.

With dilation, the pupil allows more light into the eye, in a similar fashion as opening a door to allow light inside a dark room, explains the National Eye Institute.

What Eye Drops Are Used to Dilate Pupils?

Tropicamide, brand name Mydriacyl, is one of the most commonly used eye drops for the purpose of dilating eyes. This eye drop belongs to a class of drugs known as anticholinergic, drugs that are basically known for blocking the action of a neurotransmitter known as acetylcholine.

These eye drops work by making the eye muscles incapable of responding to nerve signals, and therefore, making them become relaxed.

Another type of dilating eye drop is phenylephrine. However, according to a study, tropicamide was found to be superior in dilating pupils, with it working about twice as fast as phenylephrine with a greater absolute pupillary dilation after ten minutes.

However, phenylephrine has also its place. It can be used for those cases where one may not want to achieve maximal pupillary dilation such as needed when the patient will be driving after a dilated eye exam.

How Long Does It Take For Pupils to Dilate?

Pupil dilation usually occurs within 25 to 30 minutes. Interestingly, because Tropicamide binds with pigment, it may take longer to act on darker-colored eyes.

How Does It Feel to Have Pupils Dilated?

You will likely feel a mild stinging sensation when the drops are instilled. It is also possible to taste a medicinal taste in the mouth.

Your eyesight will become somewhat blurry and lights may bother you. You may find it helpful to wear sunglasses after the procedure to reduce discomfort and protect your eyes from bright light.

There are several eye tests that may be done with dilated eyes.

There are several eye tests that may be done with dilated eyes.

Can You Get Side Effects From Eye Dilation?

Yes, as with other drugs, the eye drops used to dilate eyes can cause side effects. The most commonly reported are the following, but more than side effects, several of these are simply signs that the medication is working (doing its job).

  • Blurry vision especially for close objects
  • Mild stinging sensation in the eyes when eye drops are applied
  • Sensitivity to light
  • Rise in intraocular pressure (as the pupils expand, the trabecular meshwork is squeezed causing pressures to go up).

Adverse Side Effects Are Uncommon

Tropicamide can cause dry mouth, raised temperature, constipation, increased heart rate, and headache, with young children and the elderly more prone to this.

However, tropicamide fortunately rarely causes the above effects listed above.

Other side effects may include nausea, vomiting, pallor, allergic reactions, and muscular rigidity.

One concern of pupil dilation is increasing intraocular pressure triggering an acute attack of angle closure glaucoma. This would cause redness, watering eyes, blurry vision, severe pain, nausea, and vomiting. This should be treated immediately.

However, according to a study, the incidence of this occurring is relatively low, especially compared to the risk of underdiagnosing vision-threatening conditions.

Can You Drive After Pupil Dilation?

It is best not to drive, as your vision will be altered. Bright lights will be bothersome. Sure, things may go well, and all is good, but if something would happen then you'd have to live with it for the rest of your life.

On top of this, if something were to happen, your insurance claim would likely be void.

It is therefore best to have a driver accompany you or you can book an Uber driver to pick you up on the way back.

Special eye drops are used to dilate eyes.

Special eye drops are used to dilate eyes.

How Long Are the Eyes Dilated?

Usually, the eyes return to normal within 4 to 8 hours. However, in some people, it may take 24 hours to wear off.

This can be due to overdosage or decreased metabolism so the medication takes longer to wear off.

Generally, lighter eyes tend to stay dilated for a longer period of time.

Are There Any Reversal Drugs?

Yes, there are 'reversal drops' which can help shorten the time it takes for pupils to return back to normal, but they come with side effects or have been taken off the market.

These may be used in rare instances such as under the threat of angle-closure glaucoma. For instance, a cholinergic agent such as pilocarpine may be used to reverse the effects of the anticholinergic drug.

This isn't offered very often because apparently, it can cause side effects (such as a reduction in visual acuity in certain subjects) and it may not be very effective in returning the dilated pupils to normal. For this reason, this drug has not gained wide acceptance.

Other preferable drugs may be adrenergic-blocking agents which relax the eye muscles (such as dapiprazole or thymoxamine).

However, the FDA has dropped dapiprazole from the market, but for reasons not related to safety and efficacy.

This means that at this time, there aren't many drugs available to reverse the effects of tropicamide.

What Do Eye Doctors Look For During a Dilated Eye Exam?

The Bottom Line

While the dilation of the eyes can be uncomfortable, it plays an important part in eye health screenings. It allows doctors to diagnose various eye diseases as well as other health conditions.

Tropicamide is a short-acting drug, and fortunately, the frequency of serious adverse events is rare.

And even if, in the rare case, a side effect would arise, an ophthalmologist's office is the best place to have it happen since you would be in the best hands.

As seen, pupil dilation has its advantages. The National Eye Institute recommends once or twice a year dilated exams for those over age 60, African Americans over age 40, and those with a family history of glaucoma.

If you dread having your eye dilated, consider that there is new technology nowadays that may allow eye doctors to take a closer look at eyes without necessary dilation in the near future.

Courtesy of retinal imaging technology, which takes digital pictures of the back of the eyes, showing the retina, optic disk, and blood vessels, eye dilation may soon be a thing of the past.


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This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2022 Adrian Rolla