An overview of Cataract

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

Most cataracts develop slowly and don't disturb your eyesight early on. But with time, cataract willeventually interfere with your vision.

At first, stronger lighting and eyeglasses can help you deal with cataracts. But if impaired visioninterferes with your usual activities, you might need cataract surgery. Fortunately, cataract surgeryis generally a safe, effective procedure.

Cataract types include:

Cataracts affecting the center of the lens (nuclear cataracts). A nuclear cataract may at first cause more nearsightedness or even a temporary improvement in your reading vision. But with time, the lens gradually turns more densely yellow and further clouds your vision.

As the cataract slowly progresses, the lens may even turn brown. Advanced yellowing or browning of the lens can lead to difficulty distinguishing between shades of color.

Cataracts that affect the edges of the lens (cortical cataracts). A cortical cataract begins as whitish, wedge-shaped opacities or streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the center and interfere with light passing through the center of the lens.

Cataracts that affect the back of the lens (posterior subcapsular cataracts). A posterior subcapsular cataract starts as a small, opaque area that usually forms near the back of the lens, right in the path of light. A posterior subcapsular cataract often interferes with your reading vision, reduces your vision in bright light, and causes glare or halos around lights at night. These types of cataracts tend to progress faster than other types do.

Cataracts you're born with (congenital cataracts). Some people are born with cataracts or develop them during childhood. These cataracts may be genetic, or associated with an intrauterine infection or trauma.

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

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

Some inherited genetic disorders that cause other health problems can increaseyour risk of cataracts. Cataracts can also be caused by other eye conditions, pasteye surgery or medical conditions such as diabetes. Long-term use of steroid medications,too, can cause cataracts to develop.

A cataract is a cloudy lens. The lens is positioned behind the colored part of your eye (iris).The lens focuses light that passes into your eye, producing clear, sharp images on the retina —the light-sensitive membrane in the eye that functions like the film in a camera.

As you age, the lenses in your eyes become less flexible, less transparent and thicker.Age-related and other medical conditions cause proteins and fibers within the lenses to breakdown and clump together, clouding the lenses.

As the cataract continues to develop, the clouding becomes denser. A cataract scatters and blocksthe light as it passes through the lens, preventing a sharply defined image from reaching your retina.As a result, your vision becomes blurred.

Cataracts generally develop in both eyes, but not always at the same rate. The cataract in one eye may bemore advanced than the other, causing a difference in vision between eyes.

1. Clouded, blurred or dim vision

2. Increasing difficulty with vision at night

3. Sensitivity to light and glare

4. Need for brightr light for reading and other activities

5. Seeing "halos" around lights

6. Frequent changes in eyeglass or contact lens prescription

7. Fading or yellowing of colors

8. Double vision in a single eye

At first, cloudiness in your vision caused by a cataract may affect only a small part of the eye's lensand you may be unaware of any vision loss. As the cataract grows larger, it clouds more of your lensand distorts the light passing through the lens. This may lead to more-noticeable symptoms.

To determine whether you have a cataract, your doctor will review your medical history and symptoms, andperform an eye examination. Your doctor may conduct several tests, including:

1. Visual acuity test : This test uses an eye chart to measure how well you can read aseries of letters. Your eyes are tested one at a time, while the other eye is covered. Using a chart or a viewingdevice with progressively smaller letters, your eye doctor determines if you have 20/20 vision or if your visionshows signs of impairment.

2. Slit-lamp examination : A slit lamp allows your eye doctor to see thestructures at the front of your eye under magnification. The microscope is called a slit lampbecause it uses an intense line of light, a slit, to illuminate your cornea, iris, lens, and thespace between your iris and cornea. The slit allows your doctor to view these structures in small sections,which makes it easier to detect any tiny abnormalities.

3. Retinal exam : To prepare for a retinal exam, your eye doctor puts drops in your eyes to openyour pupils wide (dilate). This makes it easier to examine the back of your eyes (retina). Using a slit lamp or aspecial device called an ophthalmoscope, your eye doctor can examine your lens for signs of a cataract.

4. Applanation tonometry : This test measures fluid pressure in your eye.There are multiple different devices available to do this.

When your prescription glasses can't clear your vision,the only effective treatment for cataracts is surgery.

Talk with your eye doctor about whether surgery is right for you. Most eye doctors suggestconsidering cataract surgery when your cataracts begin to affect your quality of life orinterfere with your ability to perform normal daily activities, such as reading or drivingat night.

It's up to you and your doctor to decide when cataract surgery is right for you. For most people,there is no rush to remove cataracts because they usually don't harm the eyes. But cataracts canworsen faster in people with certain conditions, including diabetes, high blood pressure or obesity.

Delaying the procedure generally won't affect how well your vision recovers if you later decide to have cataract surgery.Take time to consider the benefits and risks of cataract surgery with your doctor.

If you choose not to undergo cataract surgery now, your eye doctor may recommend periodic follow-up examsto see if your cataracts are progressing. How often you'll see your eye doctor depends on your situation.

Factors that increase your risk of cataracts include:

Increasing age

Diabetes

Excessive exposure to sunlight

Smoking

Obesity

High blood pressure

Previous eye injury or inflammation

Previous eye surgery

Prolonged use of corticosteroid medications

Drinking excessive amounts of alcohol

When your prescription glasses can't clear your vision,the only effective treatment for cataracts is surgery.

No studies have proved how to prevent cataracts or slow the progression of cataracts.But doctors think several strategies may be helpful, including:

Have regular eye examinations. Eye examinations can help detect cataracts and other eye problems at their earliest stages.Ask your doctor how often you should have an eye examination.

Quit smoking. Ask your doctor for suggestions about how to stop smoking. Medications,counseling and other strategies are available to help you.

Manage other health problems. Follow your treatment plan if you have diabetes or other medicalconditions that can increase your risk of cataracts.

Choose a healthy diet that includes plenty of fruits and vegetables. Adding a variety of colorfulfruits and vegetables to your diet ensures that you're getting many vitamins and nutrients.Fruits and vegetables have many antioxidants, which help maintain the health of your eyes.

Studies haven't proved that antioxidants in pill form can prevent cataracts. But a large population studyrecently showed that a healthy diet rich in vitamins and minerals was associated with a reduced risk of developingcataracts. Fruits and vegetables have many proven health benefits and are a safe way to increase the amount of mineralsand vitamins in your diet.

Wear sunglasses. Ultraviolet light from the sun may contribute to the development of cataracts. Wear sunglassesthat block ultraviolet B (UVB) rays when you're outdoors.

Reduce alcohol use. Excessive alcohol use can increase the risk of cataracts.