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.
What Is a Cataract?
A cataract is a dense, cloudy area that forms in the lens of the eye. A cataract begins when proteins in the eye form clumps that prevent the lens from sending clear images to the retina. The retina works by converting the light that comes through the lens into signals. It sends the signals to the optic nerve, which carries them to the brain.
It develops slowly and eventually interferes with your vision. You might end up with cataracts in both eyes, but they usually don’t form at the same time. Cataracts are common in older people.
Causes of Cataracts
There are several underlying causes of cataracts. These include:
• An overproduction of oxidants, which are oxygen molecules that have been chemically altered due to normal daily life
• Smoking
• Ultraviolet radiation
• The long-term use of steroids and other medications
• Certain diseases, such as diabetes
• Trauma
• Radiation therapy
Risk Factors of Cataracts
Risk factors associated with cataracts include:
• Older age
• Heavy alcohol use
• Smoking
• Obesity
• High blood pressure
• Excessive exposure to sunlight
• A family history of cataracts
• Diabetes
• Exposure to radiation from X-rays and cancer treatments
• Previous eye injury or inflammation
• Previous eye surgery
• Prolonged use of corticosteroid medications
How A Cataract Forms
The lens, where cataracts form, 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 tissues within the lens to break down and clump together, clouding small areas within the lens.
As the cataract continues to develop, the clouding becomes denser and involves a bigger part of the lens. A cataract scatters and blocks the 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 evenly. The cataract in one eye may be more advanced than the other, causing a difference in vision between eyes.
Types of Cataracts
There are different types of cataracts. They’re classified based on where and how they develop in your eye.
1. 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.
2. 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.
3. 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.
4. 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 also may 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.
Diagnosing Cataracts
Your doctor will perform a comprehensive eye exam to check for cataracts and to assess your vision. This will include an eye chart test to check your vision at different distances and tonometry to measure your eye pressure.
The most common tonometry test uses a painless puff of air to flatten your cornea and test your eye pressure. Your doctor will also put drops in your eyes to make your pupils bigger. This makes it easier to check the optic nerve and retina at the back of your eye for damage.
Other tests your doctor might perform include checking your sensitivity to glare and your perception of colors.
Treatment of Cataracts
If you’re unable or uninterested in surgery, your doctor may be able to help you manage your symptoms. They may suggest stronger eyeglasses, magnifying lenses, or sunglasses with an anti-glare coating.
Prevention of Cataracts
To reduce your risk of developing cataracts:
• Protect your eyes from UVB rays by wearing sunglasses outside
• Have regular eye exams
• Stop smoking
• Eat fruits and vegetables that contain antioxidants
• Maintain a healthy weight
• Keep diabetes and other medical conditions in check
Lifestyle and Home Remedies
To deal with symptoms of cataracts until you decide to have surgery, try to:
• Make sure your eyeglasses or contact lenses are the most accurate prescription possible
• Use a magnifying glass to read if you need additional help reading
• Improve the lighting in your home with more or brighter lamps
• When you go outside during the day, wear sunglasses or a broad-brimmed hat to reduce glare
• Limit your night driving
Self-care measures may help for a while, but as the cataract progresses, your vision may deteriorate further. When vision loss starts to interfere with your everyday activities, consider cataract surgery.
Outlook of a Cataract
Cataracts can interfere with daily activities and lead to blindness when left untreated. Although some stop growing, they don’t get smaller on their own and the surgical removal of cataracts is a very common procedure.
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