What is eye dilation and why is it so important? - SightMD Skip to main content

March 08, 2022

By: Jeffrey Martin, MD

What is eye dilation and why is it so important?

Woman with green eyes using eye dilation drops

What are Dilating Eye Drops?

Dilating eye drops make the pupil of the eye bigger. The pupil is the black circle in the center of the colored part of the eye. There are two main types of drops. One type causes special muscles of the iris to contract, which makes the pupil bigger (dilation). The other type prevents special muscles from making the pupil smaller, and also relaxes the eye’s ability to focus. All these changes are temporary, and usually last for a short amount of time.

How Do Eye Dilation Drops Work?

There are many different types of dilation drops that can be used, each varying in how long they last. 2.5% Phenylephrine is commonly used. This is a clear, colorless, and sterile topical ophthalmic solution that prevents the iris muscles (colored part of the eye) from constricting the pupil, thus causing dilation. When your pupils are dilated you can expect some light sensitivity, or photophobia, due to more light entering your eye. You can also expect some blurred vision which is caused by the iris muscles being unable to constrict and contract to allow you to focus.

What Should you Expect When Getting Dilated?

Dilation drops affect everyone differently and can last from a few to several hours depending on the type of dilating eye drop used and how your specific eyes react. To help with the effects of dilation, you can bring sunglasses to wear after your eye exam to help with the light sensitivity. If you are worried about having blurred vision and how long it may last, speak with your optometrist about your concerns and perhaps bring along someone who is willing to drive for you after your appointment. Like most eye drops, there may be some stinging immediately after the eye drop is used. This usually lasts only a few moments. A numbing eye drop can be used before use of the dilating drop to decrease stinging but may cause stinging of its own.

What are the side effects of eye dilation drops?

Dilation is harmless in the long term, but it does come with short-term side effects. These will usually last for about four to six hours.

Side effects of dilation include:

  • light sensitivity
  • blurry vision
  • trouble focusing on close objects
  • stinging right after the drops are put in

If you wear contact lenses, you may not be able to wear them until the dilation drops wear off.

Why is eye dilation important?

Dilation allows an eye doctor to look inside your eyes. Dilating drops widen the pupil (the black part of your eye) so that it doesn’t get smaller when your doctor shines a light at it. The widened pupil allows your doctor to use a magnifying lens to look inside your eye and at the back of your eye. They’ll look at the retina, optic nerve, blood vessels, and other parts of your eye that can’t otherwise be seen.

Dilation helps your eye doctor diagnose many eye conditions, including

  • glaucoma
  • retinal detachment
  • age-related macular degeneration
  • diabetic retinopathy

It also helps diagnose some chronic conditions that affect more than your eye, such as high blood pressure and diabetes. This is because those conditions can lead to changes in the eye. For example, high blood pressure could damage the blood vessels in your retina, which can be seen only when your eye is dilated.

Can I Drive?

Dilation doesn’t typically affect your distance vision, unless you are farsighted and don’t have glasses to correct your vision. But because your pupils can’t control the amount of light going into your eyes, the glare outside may bother you. For some people, that makes it unsafe to drive.

Dilation as a treatment

Dilating drops can also be used to treat certain eye conditions. These include eye inflammation and amblyopia, also called a lazy eye, which is a condition where one eye doesn’t properly connect with the brain. Dilating drops used as treatment have the same effects as drops used during exams.

Contact SightMD today to schedule an appointment with one of our doctors to discuss your vision health at one of our convenient locations!