Merck Manual

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The Manual's Editorial Staff

Last full review/revision May 2021| Content last modified May 2021
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What is a cataract?

A cataract is when the lens of your eye slowly gets cloudy. This does not hurt, but it causes your vision to get worse over time.

  • Among other symptoms, your vision may not be as sharp

  • An eye doctor can diagnose a cataract by examining your eyes

  • When you can no longer see well enough, the cataract can be removed

What causes a cataract?

The cause of cataracts is not always known. Often cataracts develop as you get older. However, other causes include:

What are the symptoms of a cataract?

Symptoms may vary from person to person but can include:

  • Blurry vision

  • Seeing halos and glare around lights

  • Less often, double vision

  • Colors seeming more yellow and less bright than normal

  • Rarely, pain

How can doctors tell if I have a cataract?

Doctors do a full eye exam to see if you have a cataract, where the cataract is, and how much light it’s blocking.

How do doctors treat a cataract?

At first, you might use eyeglasses or contact lenses to help you see better. There are no eye drops or medicines that will make cataracts go away. Doctors will not do surgery until your vision is very bad.

At some point, your vision may get bad enough that you feel unsafe or unable to do your daily tasks. Then doctors will do surgery to remove your cataract. During surgery, doctors replace your eye's natural lens with an artificial (man-made) one. Surgery takes about 30 minutes. You can go home the same day.

After surgery:

  • You’ll use eye drops to prevent infection and help your eye heal

  • You'll have some follow-up visits with your doctor

  • Your vision will improve within a few weeks after surgery, but you may still need glasses for reading or driving at night

  • Rarely you might have an infection, bleeding, high pressure, or swelling in your eye

  • Doctors will treat any problem that may develop

How can I prevent a cataract?

To help prevent cataracts:

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