Cataract

A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.

A cataract can occur in either or both eyes. It cannot spread from one eye to the other.

Although most cataracts are related to aging, there are other types of cataract:

1. Secondary cataract. Cataracts can form after surgery for other eye problems, such as glaucoma. Cataracts also can develop in people who have other health problems, such as diabetes. Cataracts are sometimes linked to steroid use.
2. Traumatic cataract. Cataracts can develop after an eye injury, sometimes years later.
3. Congenital cataract. Some babies are born with cataracts or develop them in childhood, often in both eyes. These cataracts may be so small that they do not affect vision. If they do, the lenses may need to be removed.
4. Radiation cataract. Cataracts can develop after exposure to some types of radiation.

Symptoms and Diagnosis

The most common symptoms of a cataract are:

• Cloudy or blurry vision.
• Colors seem faded.
• Glare. Headlights, lamps, or sunlight may appear too bright. A halo may appear around lights.
• Poor night vision.
• Double vision or multiple images in one eye. (This symptom may clear as the cataract gets larger.)
• Frequent prescription changes in your eyeglasses or contact lenses.

These symptoms also can be a sign of other eye problems. The following diagnostic methods may be used:

1. Visual acuity test. This eye chart test measures how well one can see at various distances.
2. Dilated eye exam. Drops are placed in the eyes to widen, or dilate, the pupils. The eye care professional uses a special magnifying lens to examine the retina and optic nerve for signs of damage and other eye problems. After the exam, the close-up vision may remain blurred for several hours.
3. Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to the eye for this test.

Causes

The lens lies behind the iris and the pupil (see diagram). It works much like a camera lens. It focuses light onto the retina at the back of the eye, where an image is recorded. The lens also adjusts the eye's focus, letting us see things clearly both up close and far away. The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.

But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see.

Researchers suspect that there are several causes of cataract, such as smoking and diabetes. Or, it may be that the protein in the lens just changes from the wear and tear it takes over the years.

Prevention

Wearing sunglasses and a hat with a brim to block ultraviolet sunlight may help to delay cataract. If you smoke, stop. Researchers also believe good nutrition can help reduce the risk of age-related cataract. They recommend eating green leafy vegetables, fruit, and other foods with antioxidants.

If you are age 60 or older, you should have a comprehensive dilated eye exam at least once every two years. In addition to cataract, your eye care professional can check for signs of age-related macular degeneration, glaucoma, and other vision disorders. Early treatment for many eye diseases may save your sight.

Reference:

National Eye Institute, USA.