A cataract is a clouding of the lens of the eye, which is typically clear. For people who have cataracts, seeing through cloudy lenses is like looking through a frosty or fogged-up window. Clouded vision caused by cataracts can make it more difficult to read, drive a car at night or see the expression on a friend's face.

Most cataracts develop slowly and don't disturb eyesight early on. But with time, cataracts will eventually affect vision.

At first, stronger lighting and eyeglasses can help deal with cataracts. But if impaired vision affects usual activities, cataract surgery might be needed. Fortunately, cataract surgery is generally a safe, effective procedure.

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Symptoms of cataracts include:

  • Clouded, blurred or dim vision.
  • Trouble seeing at night.
  • Sensitivity to light and glare.
  • Need for brighter light for reading and other activities.
  • Seeing "halos" around lights.
  • Frequent changes in eyeglass or contact lens prescription.
  • Fading or yellowing of colors.
  • Double vision in one eye.

At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye's lens. You may not notice any vision loss. As the cataract grows larger, it clouds more of your lens. More clouding changes the light passing through the lens. This may lead to symptoms you notice more.

When to see a doctor

Make an appointment for an eye exam if you notice any changes in your vision. If you develop sudden vision changes, such as double vision or flashes of light, sudden eye pain, or a sudden headache, see a member of your health care team right away.

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Most cataracts develop when aging or injury changes the tissue that makes up the eye's lens. Proteins and fibers in the lens begin to break down. This causes vision to become hazy or cloudy.

Some disorders passed down from parents that cause other health problems can increase your risk of cataracts. Cataracts also can be caused by other eye conditions, past eye surgery or medical conditions such as diabetes. Long-term use of steroid medicines also may cause cataracts to develop.

How a cataract forms

A cataract is a cloudy lens. The lens sits behind the colored part of your eye, called the iris. The lens focuses light that passes into your eye. This produces clear, sharp images on the back part of the eye, called the retina.

As you age, the lenses in your eyes become less flexible, less clear and thicker. Aging and some medical conditions can cause proteins and fibers within the lenses to break down and clump together. This is what causes the clouding in the lenses.

As the cataract grows, the clouding becomes worse. A cataract scatters and blocks the light as it passes through the lens. This prevents a sharply defined image from reaching your retina. As a result, your vision becomes blurred.

Cataracts usually happen in both eyes, but not always at the same rate. The cataract in one eye may be worse than the other. This causes a difference in vision between eyes.

Types of cataracts

Cataract types include:

  • Cataracts affecting the center of the lens, called nuclear cataracts. A nuclear cataract may at first cause objects far away to be blurry but objects up close to look clear. A nuclear cataract may even improve your reading vision for a short time. But with time, the lens slowly turns more yellow or brown and makes your vision worse. It may become difficult to tell colors apart.
  • Cataracts that affect the edges of the lens, called cortical cataracts. A cortical cataract begins as white, wedge-shaped spots or streaks on the outer edge of the lens cortex. As the cataract slowly grows, the streaks spread to the center and affect light passing through the lens.
  • Cataracts that affect the back of the lens, called posterior subcapsular cataracts. A posterior subcapsular cataract starts as a small spot that usually forms near the back of the lens, right in the path of light. A posterior subcapsular cataract often affects your reading vision. It also may reduce your vision in bright light and cause glare or halos around lights at night. These types of cataracts tend to grow faster than others.
  • Cataracts you're born with, called congenital cataracts. Some people are born with cataracts or develop them during childhood. These cataracts may be passed down from parents. They also may be associated with an infection or trauma while in the womb.

    These cataracts also may be due to certain conditions. These may include myotonic dystrophy, galactosemia, neurofibromatosis type 2 or rubella. Congenital cataracts don't always affect vision. If they do, they're usually removed soon after they're found.

Risk factors

Factors that increase your risk of cataracts include:

  • Increasing age.
  • Diabetes.
  • Getting too much sunlight.
  • Smoking.
  • Obesity.
  • Family history of cataracts.
  • Previous eye injury or inflammation.
  • Previous eye surgery.
  • Prolonged use of corticosteroid medicines.
  • Drinking excessive amounts of alcohol.


No studies have proved how to prevent or slow the growth of cataracts. But health care professionals think several strategies may be helpful, including:

  • Regular eye exams. Eye exams can help detect cataracts and other eye problems at their earliest stages. Ask your health care team how often you should have an eye examination.
  • Do not smoke. Ask a member of your health care team how to stop smoking. Medicines, counseling and other strategies are available to help you.
  • Manage other health problems. Follow your treatment plan if you have diabetes or other medical conditions that can increase your risk of cataracts.
  • Choose a healthy diet that includes plenty of fruits and vegetables. Adding fruits and vegetables to your diet ensures that you're getting many vitamins and nutrients. Fruits and vegetables have antioxidants. Antioxidants help maintain the health of your eyes.

    Studies haven't proved that antioxidants in pill form can prevent cataracts. But a large population study recently showed that a healthy diet rich in vitamins and minerals reduced the risk of developing cataracts. Fruits and vegetables have many proven health benefits. Eating them is a safe way to get enough minerals and vitamins in your diet.

  • Wear sunglasses. Ultraviolet light from the sun may cause cataracts. Wear sunglasses that block ultraviolet B rays when you're outdoors.
  • Reduce alcohol use. Drinking too much alcohol can increase the risk of cataracts.

Sept. 28, 2023
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  4. Jacobs DS. Cataract in adults. https://www.uptodate.com/contents/search. Accessed April 19, 2023.
  5. Cataracts. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts. Accessed April 19, 2023.
  6. Cataract in the adult eye PPP. American Academy of Ophthalmology. https://www.aao.org/education/preferred-practice-pattern/cataract-in-adult-eye-ppp-2021-in-press. Accessed April 19, 2023.
  7. Causes of cataracts. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts/causes-cataracts. Accessed April 19, 2023.


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