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How Long Your Eyes Stay Dilated After Eye Exam

How Long Your Eyes Stay Dilated After Eye Exam

Why your eyes look bigger at night?

The pupil is the dark circle at the centre of the iris of your eye. The whole job of the iris and pupil is to control the amount of light that gets into the eye. Normally, your pupils change in sizes depending on the amount of light around you.

In low light condition, your pupils dilate, which is controlled by the muscle in your iris to let in more light. Eye dilation is also known as mydriasis in medical term.

When it’s bright, the pupils constrict to allow less light.

Besides the change in the light, mydriasis also happens in response to medications, injuries or other drugs.

Eye Exams: Why do you need to dilate pupils?

An eye doctor can only see your optic nerve and macula with a limited view when the pupil constricts.

A dilated pupil allows the doctor to see the entire retina. By giving a closer look at the inside of the eye, they can diagnose and treat eye diseases such as diabetes, eye tumours, high blood pressure, infectious diseases, macular degeneration, retinal detachment, vasculitis, glaucoma, etc.

Also, while dilated, focusing muscles of the eyes allows more accurate measurement of refractive error in children.

Dilated pupils are mostly achieved by eye-drops.

There are two types of drops that cause mydriasis:

The parasympatholytic drops, including atropine, homatropine, cyclopentolate and tropicamide, block the activity of the parasympathetic nervous system to relax the muscles that make the pupil constrict.  Besides being typically used during dilated fundus examination, these drops may also be used before or after eye surgery.

Cycloplegic drops are also used to treat anterior uveitis, posterior synechiae and inflammation in the anterior chamber of the eye.

When treating the progression of nearsightedness (progressive myopia), a much more diluted concentration of atropine is used to limit the potential side effects, including fever, dry mouth, flushing of the face, and a rapid pulse. In some rare cases, atropine can cause a new onset of eye crossing (esotropia), or worsen an existing esotropia.

(©Coka – Fotolia/stock.adobe.com)
woman applying eyedroppes, close up

On the other hand, the sympathomimetic drops, such as phenylephrine, directly activate the sympathetic nervous system inside your eye to stimulate the contraction of the muscles that dilate the pupil. Phenylephrine is often used in combination with tropicamide as a synergist when tropicamide alone is not sufficient.

Dilating the eyes involves the use of two or three drops administered directly into the eye. Depending on what the doctor is examining and how large the pupil needs to be, different types of eye drops may be used, including:

  • Phenylephrine
  • Tropicamide
  • Hydroxyamphetamine
  • Cyclopentolate
  • Atropine

How long your eyes stay dilated after eye exam

Dilating eye drops usually last from 4 to 24 hours, depending on the strength of the drops and how different eyes react.

People with lighter colored eyes (blue, green, hazel) might have longer pupil dilation that lasts more than 24 hours while dark-colored eyes (brown, black) have shorter dilation periods.

Children, meanwhile, are often dilated with stronger and longer drops than adults do to improve the accuracy of the exam. Don’t freak out if your kids wake up in the morning after an exam with their pupils still wide open.

Dilating eye drops that used to treat certain eye diseases, such as amblyopia and eye inflammation may take even up to 2 weeks to wear off. Even though these therapeutic drops have a longer duration of action, the treatment requires daily administration of the drop.

Your vision will be blurry while having dilated pupils. Your pupils will also be more sensitive to light. These side effects gradually fade away but it’s best to have someone drive you and wear sunglasses after eye exam.

Try to avoid reading while having blurred vision. When used for examinations, it’s unlikely for drops to cause allergic reactions but lid swelling and red eyes.

When to book an eye exam

You should take dilated eye exam in every comprehensive eye examination visit which is at least biannually. This way the doctors can gather a lot of information about your eye health and detect eye diseases such as glaucoma, cataract, macular degeneration, systematic diseases like diabetes, hypertension HIV etc.

Adults with risk factors including family history of eye disease, diabetes or high blood pressure, prescription or nonprescription drugs consumption that may have visual related effects and previous eye injuries should have more frequent exams.

If you’ve had a head injury and one of your pupils is bigger than the other, get emergency help. The doctor will examine your eyes with other tests such as computed tomography or MRI scan to look for problems with your brain.

How to Manage Dilated Pupils

  • If your pupils dilate after using medicine, they should return to normal size after the effect wears off.
  • Try to use the medication that won’t affect your eyes or avoid the drug if you can.
  • Protect your eyes while they are dilated as they are more sensitive to light than usual with sunglasses.
  • Try to avoid driving after the eye exam as the dilating drops will affect your vision for a couple of hours.
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