Illustration of the human eye.

A bout 24.5 million people in the U.S. have cataracts, a vision-blurring cloudy spot on the lens of the eye. “When you’re young, the lens is clear, like a raw egg white,” says Uday Devgan, M.D., a cataract surgeon and professor of ophthalmology at UCLA. “But over time, it becomes opaque.”

Surgery to replace the cloudy lens with an artificial one can improve vision. While this is a fairly simple outpatient procedure—and one of the most common surgeries in the U.S.—there are decisions to make and occasional complications. Here's what to know about cataract surgery.

When to Consider Cataract Surgery

Signs that you may have cataracts or that existing cataracts are worsening can be subtle. They include increasing difficulty seeing well at night (especially when facing an oncoming car’s headlights), having to make the text on your computer screen larger, and sensing that colors are fading.

When might cataract surgery be appropriate? “If you’re happy with your current vision, don’t do anything,” Devgan says. But if vision problems are affecting activities such as reading or driving, consider seeing an ophthalmologist to discuss cataract surgery.

What to Expect Before Cataract Surgery

If you and the ophthalmologist agree that you’d benefit from cataract surgery, he or she will give you a thorough eye exam a week or two before the procedure.

Your doctor may also recommend a test like an electrocardiogram (EKG). According to the American Academy of Ophthalmology, tests such as an EKG or a complete blood count may make surgical procedures safer for some people, but most don’t need them before eye surgery.

more on eye health

And having such preop tests needlessly may have negative effects. For instance, research published online in June in JAMA Internal Medicine found that nearly 16 percent of older adults without heart disease who had an EKG before cataract surgery had one or more potential “cascade events” within 90 days, such as medical treatment, additional testing, doctors’ office visits, or hospitalization. 

You’ll also choose new lenses before cataract surgery. Standard monofocal lenses, which usually help with distance vision, are often included in the price of surgery and provide excellent clarity. But you may still need glasses for reading afterward, says Neal Shorstein, M.D., an ophthalmologist and associate chief of quality for Kaiser Permanente in Walnut Creek, Calif.

Multifocal lenses, which can help with near and far vision, may eliminate the need for eyeglasses but can cost more than $2,000 an eye out of pocket. And you may still have difficulties with nighttime driving glare afterward.

During Surgery and After

Cataract surgery is usually done at outpatient surgical centers, but some eye surgeons do the procedure in a hospital or private medical office.

“There’s no research to support better outcomes in one venue over another,” Shorstein says.

Most people receive a light sedative and an anesthetic to numb the eye, says Devgan. The surgery takes less than 30 minutes, and you should have improved vision the day after. (For surgery on both eyes, the procedures are often performed several weeks apart.)

Because the sedation may leave you groggy, you’ll need a ride home and should take it easy for at least a few hours.

Cut Complication Risks

Overall, the likelihood of complications after cataract surgery is low. But call your eye doctor right away if you notice increased redness, pain, or discomfort, decreasing vision, or other concerns.

Some research estimates that about 1 percent of cataract surgery patients have some temporary vision loss from macular edema (eye swelling), and less than 1 percent develop an eye infection.

Your doctor will probably prescribe corticosteroid eye drops to lower the chance of macular edema and possibly nonsteroidal anti-inflammatory eye drops. Antibiotic eye drops can help ward off infection.

Some research shows that many people use eye drops incorrectly, so have your doctor show you how. “Wash your hands thoroughly before putting in eye drops,” Shorstein says, “and avoid touching your eyeball or any other surface with the eye-dropper tip.”

Older research suggests that droopy eyelids may affect 10 percent or more of people after surgery (usually returning to normal within six months).

But Devgan says droopy eyelids after surgery are rare today. If you experience this, your doctor might prescribe apraclonidine eye drops to reduce droopiness short term.

Editor’s Note: A version of this article also appeared in the April 2018 issue of Consumer Reports On Health