A cataract is a clouding of the normally clear lens of your eye. Looking through a cloudy lens is like trying to see through a frosty or fogged-up window. Clouded vision can make it more difficult to read, drive a car — especially at night — or see the expression on a friend’s face. Cataract commonly affect distance vision and cause problems with glare. They generally don’t cause surface irritation or pain.
Cataract is a normal part of getting older. About half of Americans older than 65 have some degree of clouding of the lens. After age 75, as many as 70 percent of Americans have cataracts that are significant enough to impair their vision.
Most cataracts develop slowly and don’t disturb your eyesight early on. But as the clouding progresses, the cataract eventually interferes with your vision. At first, the cloudiness may affect only a small part of the lens and you may be unaware of any vision loss. Over time, however, as the cataract grows larger, it clouds more of your lens. When significantly less light reaches your retina, your vision becomes impaired.In the early stages, stronger lighting and eyeglasses can help you deal with the vision problems. But at some point, if impaired vision jeopardizes your normal lifestyle, you might need surgery. Fortunately, cataract removal is one of the safest, most effective and most common surgical procedures.

 
Symptoms of a cataract include:
Clouded, blurred or dim vision.
Increasing difficulty with vision at night.
Sensitivity to light and glare.
Halos around lights.
The need for brighter light for reading and other activities.
Frequent changes in eyeglass or contact lens prescription.
Fading or yellowing of colors.
Double vision in a single eye.
If you have a cataract, light from the sun, lamps or oncoming headlights may seem too bright. Glare and halos around lights can make driving uncomfortable and dangerous. You may experience eyestrain or find yourself blinking more often to clear your vision.
Cataracts don’t typically cause any change in the appearance of your eye. Pain, redness, itching, irritation, aching in your eye or a discharge from your eye aren’t signs or symptoms of a cataract, but may be signs and symptoms of other eye disorders.

A cataract is not dangerous to the physical health of your eye unless the cataract becomes completely white, a condition known as an overripe (hypermature) cataract. This can cause inflammation, pain and headache. A hypermature cataract is very uncommon, but it requires removal if it’s associated with inflammation or pain.

Causes
A cataract can develop in one or both eyes. However, in most cases - except for those caused by injury or trauma - cataracts tend to develop symmetrically in both eyes.
When your eyes work properly, light passes through the cornea and the pupil to the lens. The lens focuses this light, producing clear, sharp images on the retina - the light-sensitive membrane on the back inside wall of your eyeball that functions like the film of a camera. As a cataract develops, the lens becomes clouded, which scatters the light and prevents a sharply defined image from reaching your retina. As a result, your vision becomes blurred.

Risk Factors
Everyone is at risk of developing cataracts simply because age is the single greatest risk factor. By age 65 about half of all Americans have developed some degree of lens clouding, although it may not impair vision.
Other factors that increase your risk of cataracts include: Diabetes, family history of cataracts , previous eye injury, surgery or inflammation, prolonged use of corticosteroids, exposure to ionizing radiation, smoking.

Diagnosis
An eye specialist can detect and track the development of cataracts during routine eye exams. Have your eyes examined: Every two to four years until age 65 and every one to two years at age 65 and older The only way to know for sure if you have a cataract is to have an eye examination that includes several tests:
- Visual Acuity test. Acuity refers to the sharpness of your vision or how clearly you see an object. In this test, your eye doctor checks to see how well you read letters from across the room. Your eyes are tested one at a time, while the other eye is covered. Using the chart with progressively smaller letters from top to bottom, your eye doctor determines if you have 20/20 vision or less visual acuity.
- Slit-lamp examination. A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification. The microscope is called a slit lamp because it uses an intense line of light - a slit - to illuminate your cornea, iris, lens and the space between your iris and cornea. The slit allows your doctor to view these structures in small sections, which makes it easier to detect any small abnormalities.
- Retinal examination. Using a slit lamp or a special device called an ophthalmoscope, he or she can examine your lens for signs of a cataract and, if needed, determine how dense the clouding is. Your eye doctor will also check for glaucoma and, if you have blurred vision or discomfort, check for other problems involving the retina and the optic nerve.
If you have a cataract, you can discuss treatment options with your eye doctor. If - in addition to having a cataract - you have other eye conditions that limit your vision, such as macular degeneration or advanced glaucoma, removing the cataract may not improve vision, and cataract surgery may provide disappointing results.

Treatment
The only effective treatment for a cataract is surgery to remove the clouded lens, which usually includes replacing the lens with a clear lens implant. Sometimes cataracts are removed without reinserting implant lenses. In such cases, vision can be corrected with eyeglasses or contact lenses. Phacoemulsification is actually the golden standard surgical procedures worldwide. There are several techniques to remove cataract and replace it with the implantation of an Intra-Ocular Lens (IOL), all of which have been demonstrated to be succesfull.
Cataracts can't be cured with medications, dietary supplements, exercise or optical devices. In the early stages of a cataract when symptoms are mild, a good understanding of the condition and a willingness to adjust your lifestyle can help. Some self-care approaches, such as using a magnifying glass to read or improving the lighting in your home, may help you deal with the effects of having a cataract.

Prevention
Most cataracts occur with age and can't be avoided altogether. Regular eye exams remain the key to early detection. If you're over age 65, schedule eye exams at least every other year. You can take steps to help slow or prevent the development of cataracts:
Don't smoke. Smoking produces free radicals, increasing your risk of cataracts. Eat a balanced diet. Include plenty of fruits and vegetables. Some scientific evidence suggests that eating lots of fruits and vegetables may have a modest effect in preventing cataract development. Protect yourself from the sun. Ultraviolet light may contribute to the development of cataracts. Whenever possible, wear sunglasses when you're outdoors. Take care of other health problems. Follow your treatment plan if you have diabetes or other medical conditions.
Researchers are continuing to explore new ways to prevent and treat cataracts, such as developing medications that would reduce or eliminate the need for surgery. But, until such a treatment exists, your chances of fully restoring your vision with cataract surgery are excellent if you have no other eye diseases.