A cataract is a clouding of the eye's lens, which is typically clear. It's the leading cause of blindness worldwide and the leading cause of vision loss in the United States. Cataracts can occur at any age and can be present at birth.

At first, the cloudiness in vision caused by a cataract may affect only a small part of the eye's lens. Vision loss may be slight at first. As the cataract progresses, it clouds more of the lens. More clouding changes the light passing through the lens.
For people who have cataracts, seeing through cloudy lenses is like looking through a frosty or fogged-up window. Clouded vision caused by a cataract can make it hard to read, drive a car at night or see a computer screen.
Symptoms of cataracts include:
- Clouded, blurred or dim vision.
- Need for brighter light for reading and other activities.
- Trouble seeing in sunlight or bright lights.
- Trouble seeing at night.
- Halos or starbursts around lights at night.
- Frequent changes in eyeglass or contact lens prescription.
- Fading or yellowing of colors.
- Double vision in one eye.
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. Removing cataracts is a widely available treatment. Cataract surgery is generally a safe, effective procedure.
An estimated 20.5 million (17.2%) Americans aged 40 years and older have cataract in one or both eyes, and 6.1 million (5.1%) have had their lens removed by surgery.
Cataracts most often affects older adults. Other factors that increase your risk of cataracts include:
- Diabetes.
- Exposure to sunlight.
- Smoking and other tobacco use.
- Obesity.
- Family history of cataracts.
- Previous eye injury, disease or surgery.
- Prolonged use of corticosteroid medicines.
- Drinking excessive amounts of alcohol.
How does a cataract form? The lens sits behind the colored part of your eye, called the iris. The lens focuses light that passes into your eye. This light is focused on the back part of the eye, called the retina.
As you age, the lenses in your eyes become less flexible, thicker and less clear. Aging and some medical conditions can cause proteins and fibers within a lens to break down and clump together. This is what causes the clouding in a lens.
As the cataract grows, the clouding becomes worse. A cataract scatters and blocks the light as it passes through the lens. This prevents a clearly 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.
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, seek medical help right away.





