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

Symptoms Signs and symptoms of cataracts include:

- Clouded, blurred or dim vision
- Increasing difficulty with vision at night
- Sensitivity to light and glare
- Seeing "halos" around lights
-Frequent changes in eyeglass or contact lens prescription
- Fading or yellowing of colors
- Double vision in a single eye
- At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye's lens and you may be unaware of any vision loss. As the cataract grows larger, it clouds more of your lens and distorts the light passing through the lens. This may lead to signs and symptoms you're more likely to notice.

Types of cataracts

Cataracts that affect the center of the lens (nuclear cataracts).

Cataracts that affect the edges of the lens (cortical cataracts).

Cataracts that affect the back of the lens (posterior subcapsular cataracts).

Cataracts you're born with (congenital cataracts).

These cataracts also may be due to certain conditions, such as myotonic dystrophy, galactosemia, Lowe's syndrome or rubella. Congenital cataracts don't always affect vision, but if they do they're usually removed soon after detection.

Risk factors Factors that increase your risk of cataracts include:

- Increasing age
- Diabetes
- Drinking excessive amounts of alcohol
- Excessive exposure to sunlight
- Exposure to ionizing radiation, such as that used in X-rays and cancer radiation therapy
- Family history of cataracts
- High blood pressure
- Obesity
- Previous eye injury or inflammation
- Previous eye surgery
- Prolonged use of corticosteroid medications
- Smoking