How long does eye dilation last? What to expect after the drops

For most adults, the drops used to widen the pupils during an eye exam wear off in about 4 to 6 hours, though it can take longer. During that time light feels harsh and close-up things look blurry, so reading, screens and driving are all harder than usual. Children, people with lighter-colored eyes and anyone given stronger drops often stay dilated longer, sometimes until the next day.

By your sixties, a dilated exam tends to become a regular part of eye checks rather than a rare event. My years as a newspaper reporter left me liking to know what will happen before it happens, so here it is in order: why eye doctors use the drops, what they feel like, how long they last, how to get home, what to do with the rest of the day, and the few signs that mean you need help quickly.

Why eye doctors widen the pupil

The pupil is the opening through which the eye doctor looks into your eye. Under the bright light of the examination lamp it shrinks, which leaves only a narrow view of the back of the eye. Dilating drops hold the pupil open so the doctor can see the retina, the optic nerve where it leaves the eye, the blood vessels, and the outer edges of the retina, which are out of sight through a small pupil.

Common reasons for a dilated exam include:

• Diabetes. Early diabetic retinopathy has no symptoms, so people with diabetes are usually advised to have a dilated eye exam at least once a year, or as often as their eye doctor advises. The column on diabetic retinopathy checks explains why.
• Glaucoma, or a suspicion of it, where the look of the optic nerve matters. The column on glaucoma after 40 covers that.
• New floaters or flashes of light, since retinal tears often form near the edges of the retina. See floaters and retinal detachment.
• Checks for macular degeneration and other changes that become more common with age, including a first full exam around 40.
• Eye exams for children, where the drops also relax the eye's focusing muscle so the prescription can be measured accurately.

Some drops mainly widen the pupil. Others also relax the focusing muscle for a while, which is why close work blurs. Your eye doctor chooses which to use, and decides whether you need dilating at all. Your first eye exam walks through the rest of a typical visit.

What the drops feel like

Tests that need your pupils at their normal size, such as reading the letter chart, are usually done first. Then the drops go in. They often sting for a few seconds, and some clinics put in a numbing drop beforehand. A faint bitter taste at the back of the throat is common too, because tears drain from the eyes into the nose.

The drops take a while to work, often about 15 to 30 minutes, so expect to sit in the waiting room again. Once they take effect, bright light feels glaring and close-up things blur. Distance vision is often less affected, though it can look hazy too. None of this is usually painful.

If you wear contact lenses, you may be asked to take them out before the drops. Bring your glasses and a lens case, and ask when you can put the lenses back in.

How long it lasts, and why it varies

For most adults, the effect typically lasts about 4 to 6 hours. It can be longer, and it varies from person to person and from one visit to the next. Three things make the biggest difference.

• The type and strength of the drops. Drops that also relax focusing tend to last longer, and stronger drops are sometimes needed for a thorough exam.
• Eye color. Lighter eyes, such as blue or green, often stay dilated longer, while darker eyes can take longer to dilate in the first place.
• Age. Children are often given stronger drops, and their pupils can stay wide into the next day.

The two effects do not always fade together. You may find you can read again while light still feels too bright, or the other way around. If your pupils still look large or your vision has not come back by the next day, and the clinic did not tell you to expect that, call them for advice.

Getting home: driving and sunglasses

Many eye doctors advise not driving until your vision is back to normal. Glare from the sun and from headlights, combined with blur, makes it hard to judge distances and read road signs. Advice and rules vary from place to place, so ask the clinic, and plan as if you will not be driving yourself. The same goes for cycling and motorbikes.

The simplest plan is to ask when you book whether dilation is likely, then arrange a ride, public transport or a taxi. If driving yourself is the only way to get there, say so when you book, since the clinic may be able to arrange things differently. Finding an eye doctor and planning a visit has more on planning around an appointment.

Sunglasses make the trip home far more comfortable, even on a cloudy day. Some clinics hand out disposable shades, but a pair of your own fits better and keeps out more light at the sides. Look for "UV400" or "100% UVA/UVB" on the label; a darker lens is not the same as a more protective one. Polarized UV400 sunglasses also cut glare from wet roads and water. A hat with a brim helps as well.

Sunglasses ease the glare. They do nothing for the blur, so they do not make it safe to drive. On foot, take curbs and steps slowly, since edges are harder to judge in bright sun, and if someone came with you, an arm to hold is welcome.

Work, screens and reading afterward

Plan for the rest of the day to be light. If you are taking time off work, half a day is safer than an hour, and eye care around a working week has ideas for fitting appointments in.

Screens are hard with dilated eyes: they look too bright and the text blurs. Turn the brightness down, make the text larger, or set the screen aside for a few hours. A phone call is easier than a long email. Close reading is hardest of all. Reading glasses may help a little, but expect small print to be a struggle until the drops wear off.

A few things make the day easier:

• Fill in forms and read anything you need to sign before the drops go in.
• Ask the eye doctor to go over the results and next steps out loud, or bring someone who can take notes, since reading a leaflet afterward will be hard.
• Book your next appointment at the desk before you leave.
• Leave sharp knives, sewing and paperwork for another day.

When to see an eye doctor, and what is urgent

Side effects of dilating drops are usually mild and pass as the drops wear off. Rarely, in an eye with a narrow drainage angle, widening the pupil can set off a sudden rise in eye pressure called acute angle-closure glaucoma. Eye doctors watch for this risk. If you have been told you have narrow angles, or have had laser treatment for them, say so before the drops go in, and mention any reaction to eye drops you have had in the past.

Go to an emergency department, or call your local emergency number (such as 911, 999, 112, or 119 in Japan), if after dilation you have:

• severe eye pain, especially with a red eye and blurred vision
• halos or rainbow rings around lights
• a headache with nausea or vomiting

This can come on after you are home. Do not wait for the drops to wear off. Treat sudden loss of vision in one eye as an emergency too, even if it returns within minutes, since it can be a warning sign of stroke.

Some symptoms are not caused by the drops at all and should not be blamed on them. See an eye doctor the same day for new flashes of light, a sudden shower of floaters, or a shadow like a curtain across part of your vision. For swollen, itchy or very red eyelids after the drops, call the clinic for advice. Eye emergencies and first aid covers what to do while you get help.

Questions people ask

Can I go back to work after a dilated eye exam?

Many people can manage simple tasks, but screens and paperwork are hard for several hours, and anything that needs sharp close vision or driving should wait. Planning half a day off is the easy answer.

Is it safe to drive with dilated eyes if I wear sunglasses?

Sunglasses reduce glare but not blur. Many eye doctors advise waiting until your vision is back to normal before driving, so arrange another way home and ask the clinic if you are unsure.

Can I have a retinal photo instead of drops?

Some clinics take wide-field photographs of the retina, which can show a large part of it without drops or with less dilation. They are useful, but they do not always replace a dilated exam. Your eye doctor will decide which you need, and when.

Sources

• American Academy of Ophthalmology patient information on eye exams (aao.org/eye-health)
• National Eye Institute information on dilated eye exams (nei.nih.gov)