This article will go over why you might need to have your pupils dilated for an eye exam, what to expect, and how long recovery takes.
Why Do I Need to Have My Pupils Dilated?
Dilation is a key part of a comprehensive eye exam. It allows providers to identify and diagnose eye problems that they may not be able to see otherwise.
The National Eye Institute recommends that adults regularly have these exams starting at age 40 to 60. Children are typically screened for vision problems regularly as well.
How Eye Pupils Work
The pupil is kind of like a camera aperture—it gets bigger or smaller depending on how much light is needed. To do this, the pupil goes through either miosis (the pupil constricts and closes) or mydriasis (the pupil dilates and opens).
The size of the pupil is controlled by both the body’s “fight or flight” response (sympathetic nervous system) and the opposite response where the body slows high energy functions (parasympathetic nervous system).
Your pupil size can change for many reasons. For example, it can adjust in response to the amount of light it is exposed to. It can also change if you get excited, such as in moments of physical stress, emotional stress, or feeling pain.
It’s thought that the “fight or flight” response is an evolutionary advantage. By allowing more light into the eyes, the body can react more readily to possible danger.
How Long Does Pupil Dilation Last?
Dilating the eyes is an important part of an eye exam. You will have two or three drops put directly into each eye.
Depending on what your provider is trying to see and how large your pupil needs to be, different types of eye drops can be used:
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Eye drops are put in both eyes so that the retina, macula, and optic nerve can be looked at closely using a handheld light and magnifying lens.
While the dilation itself is not painful, it can be very uncomfortable because your eye is unable to protect itself from light.
How long your eyes will remain dilated depends on the type of drops used, as well as the color of your eyes. Dark-colored eyes have shorter dilation periods (typically for two to four hours) than light-colored eyes (for up to eight hours).
Children’s eyes are often dilated using stronger drops to improve the accuracy of the exam. It is not uncommon for some kids to wake up the morning after an exam with their pupils still wide open.
A medication called Rev-Eyes (dapiprozole) used be used to reverse pupil dilation in one to two hours. While the medication did work and was considered safe, it had side effects and was costly, so it’s no longer used.
What If My Pupils Stay Dilated?
Most, but not all, dilation drops cause a side effect called cycloplegia. Cycloplegia is the temporary paralysis of the muscle that allows the eye to focus on near objects. This effect can last for hours, but for some people, it can take several days for vision to fully go back to normal.
There are situations in which a provider will want to intentionally cause cycloplegia. One example is in young children whose focusing mechanism is so strong that it is often hard to measure their vision or refractive error.
Cycloplegic drops can also be used to treat eye diseases or trauma that cause acute pain and light sensitivity— for example, a condition called uveitis which is inflammation of the middle layer of the eye (uvea).
In some cases, the duration of pupillary dilation is much longer than the norm. For example, some people may naturally be more sensitive to eye-dilating medication and the effects may last a week or more. It’s also possible to be allergic to the ingredients in the drops.
Pediatric eye providers may use the drops to treat a condition that causes reduced vision in a child—for example, amblyopia. These drops are prescribed for much longer—up to several months in some cases.
Summary
Pupil dilation is an important part of a routine eye exam because it lets providers get a better look at the structures in the eye that would be hard to examine otherwise.
However, since your vision will be blurry and you might be sensitive to light, you may not feel up to driving. If you aren’t sure how you will react to the drops, ask someone to drive you to and from your eye exam appointment.
The drops used to dilate the pupils usually wear off after a few hours, but sometimes the effects last days. It’s not common but in some people who are very sensitive to the drops, the effects can be felt for a week or longer.
After an eye exam, your provider will give you some special sunglasses to wear. This can help you cope with blurry vision and sensitivity to light until your eyes go back to normal. If your vision does not seem to be going back to normal within a day or so, give your provider’s office a call.
