How Long Do Pupils Remain Dilated After an Eye Exam?

Drug type and even eye color can determine the duration

Eye drops
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Dilating the pupils of the eyes helps an ophthalmologist view the internal structures, including the lens, optic nerve, blood vessels, and retina. Dilation involves the use of special eye drops that either stimulate contraction of the muscles surrounding the pupil and relaxes the muscles so that they open.

Dilation is a key component of a comprehensive eye exam, allowing doctors to identify and diagnose eye problems that they may otherwise not see.

The American Academy of Ophthalmology currently recommends that adults regularly undergo such exams starting at age 40.

Understand the Pupil

The pupil is similar to camera aperture in that it becomes bigger or smaller, depending on how much light is needed. To do this, the pupil will undergo miosis, in which the constriction of pupil causes it to close, or mydriasis, in which is the dilation of the pupil allows it to open.

The pupil size is controlled by both the sympathetic nervous system (the "fight or flight" response) and the parasympathetic nervous system (the converse response in which the body slows high energy functions).

The pupil size can change for many reasons. It could adjust in response to the amount of light it is exposed to. It can also change when a person becomes excited, such as in response to sexual stimuli, or is faced with emotional stress. It is believed the "fight or flight" response is an evolutionary one, allowing more light into the eye so that the body can react more readily to potential harms.

Common Duration of Pupil Dilation

Dilating the eyes is a central part of an eye exam. It involves the administration of two or three drops administered directly into the eye. Depending on what the doctor is trying to achieve and how large the pupil needs to be, different types of eye drops may be used, including:

  • Phenylephrine
  • Tropicamide
  • Hydroxyamphetamine
  • Cyclopentolate
  • Atropine

Eye drops are placed in both eyes so that the retina, macula, and optic nerve can be examined closely using a handheld light and magnifying lens. While the dilation itself is not painful, it can be incredibly uncomfortable as the eye has no means by which to protect itself from light.

After a dilated eye exam, your pupils will normally remain open for about three to four hours, sometimes longer. This time varies according to the type of drops used, as well as the color of your eyes. By and large, dark-colored eyes have shorter dilation periods, while light-colored eyes may stay open up to eight hours.

Children, meanwhile, are often dilated with 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.

Uncommon Duration of Pupil Dilation

Most, but not all, drops cause a side effect called cycloplegia. Cycloplegia is the temporary paralysis of the muscle which allows the eye to focus on near objects. In some people, this effect can last for hours. In others, it may take several days for the vision to fully normalize.

There are situations where a doctor will want to intentionally cause cycloplegia.

One such example is in young children whose focusing mechanism is so strong that it is often difficult to measure their vision or refractive error. Cycloplegic drops may also be used to eye diseases or trauma that cause acute pain and light sensitivity. One such condition is called uveitis, the inflammation of the middle layer of the eye (uvea).

Pediatric eye doctors may also use them to treat a condition called lazy eye in which a child develops reduced vision for any number of reasons. These types of drops are prescribed for much longer periods of time, up to several months in some cases.

For most people, the side effect is bothersome but not intolerable.

To deal with the blurred vision and sensitivity to light, disposable sunglasses are usually provided to help reduce short-term discomfort. Unlike regular sunglasses, these block off peripheral light from the side of the lenses as well as the front.

Sources:

Cunningham, E. and Riordan-Eva, P. Vaughan & Asbury's General Ophthalmology. (18th Edition). New York: McGraw-Hill Medical; 2011; ISBN 10:0071634207,

National Eye Institute: National Institutes of Health. "What is a comprehensive dilated eye exam?" Bethesda, Maryland; 2014.

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