Your Healthy Eyes - Cataracts
A cataract is a clouding of the eye's normally clear lens, leading to a progressive blurring or dimming of vision. It is the world’s leading cause of blindness and among the most common conditions related to aging – by age 65, you have a 50 percent chance of developing a cataract and by age 75, it jumps to 70 percent.
Cataracts can also result from injury, chronic eye diseases such as retinitis pigmentosa and ailments such as diabetes, or past use of corticosteroid medications or radiation treatments. Some researchers believe that lifestyle habits such as smoking and not wearing sunglasses to protect eyes against ultraviolet light are also risk factors.
A cataract occurs when proteins in the lens begin to clump together, forming a cloudy area. As these clumps grow, they interfere with vision by distorting or blocking the passage of light. Many cataracts begin to form in your 40s or 50s, but don’t affect vision until years later. Cataracts can occur in infants, usually the result of an infection during pregnancy such as toxoplasmosis, rubella, syphilis or herpes simplex. In children, a cataract can also result from metabolic disease.
There are three primary types:
- Nuclear cataracts are the most common, typically known as "age-related cataract." Found in the center of the lens, they intefere with the ability to see distant objects. Interestingly, while the cataract is progressing, reading vision may temporarily improve because as the lens becomes more dense and cloudy, it changes the eye's ability to focus, making it clearer up close than at far distances. This symptom is often referred to as "second sight."
A nuclear cataract clouds the lens in the center.
- Cortical cataracts begin in the lens's outer rim and grow "spokes" toward the central core. These spokes block light, causing glare and loss of contrast. Both near and distance vision are slowly disrupted. Diabetics often develop this type of cataract.
A cortical cataract develops spokes from the center of the lens outward.
- Subcapsular cataracts affect the back of your lens and usually progress more quickly than other types. Subcapsular cataracts cause blurriness and glare, and are more likely to strike those with diabetes, extreme nearsightedness, retinitus pigmentosa or people who take steroid medications.
A subcapsular cataract builds up on the back of the lens.
A cataract starts out small and initially has little or no effect on vision. As the cataract grows and clouds more of the lens – what doctors call "ripens" – it will be harder to read and do other normal tasks. The word "cataract" means waterfall and for people with a ripe cataract, it is like trying to see through a waterfall or wall of fog. Other symptoms include:
- Blurred vision, as if you are looking through a cloudy piece of glass
- Double vision (diplopia)
- A sense that colors appear faded and decreased ability to distinguish some colors
- Seeing halos around lights
- Glare or sensitivity to light or from oncoming headlights while driving
- Difficulty seeing at night
There is no way to prevent age-related cataracts, but several factors can increase your risk of developing them sooner, or developing other types of cataracts. If you have diabetes, you need to tightly control your blood sugar level. Women can reduce risk of congenital cataracts with rubella immunization before becoming pregnant and monitoring conditions such as herpes. Others factors that can play a role in prevention:
- Avoiding eye injuries, such as a blow or other trauma
- Not smoking
- Limiting or eliminating use of corticosteroids, major tranquilizers and diuretics
- Protecting eyes with quality sunglasses, especially if you live at a high altitude or spend a lot of time outdoors
- Avoiding alcohol abuse
- Eating a healthy diet. Although there is no definitive proof, some studies suggest that "antioxidant" nutrients such vitamin C may play a preventative role.
In the early stages until the cataract ripens, your doctor may recommend stronger eyeglasses, using eye drops to widen the pupil and let in more light or adjusting lighting to reduce glare. When cataracts disrupt your daily life, it may be time for cataract-removal surgery, one of the most frequent procedures done in the U.S. If both eyes are affected, the surgeries are performed on different days.
More than 1.5 million Americans undergo surgery each year to remove the clouded lens, which is usually replaced with a clear, plastic intraocular lens (IOL). With an IOL, vision is restored to 20/40 or better in more than 90 percent of cases. You cannot see or feel the lens and it needs no special care. For those unable to wear an IOL, special glasses with powerful magnification or contact lenses are used.
Cataract surgery falls into two groups:
- Intracapsular: Both the lens and the protective capsule that surrounds it are removed. Once standard, this has been largely replaced by extracapsular surgery. Those who require intracapsular surgery may not be eligible for IOLs and instead need specially designed glasses or contacts.
- Extracapsular: Only the lens is removed. The front of the capsule is opened and ultrasonic waves break the lens into pieces (a process called "phacoemulsification"). The pieces are then vacuumed out of the capsule. The normal lens capsule surrounding the lens is left intact.
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