A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil. 

Types of cataracts include:
A subcapsular cataract occurs at the back of the lens.  People with diabetes, high farsightedness or retinitis pigmentosa, or those taking high doses of steroid medications have a greater risk of developing a subcapsular cataract.
A nuclear cataract forms deep in the central zone (nucleus) of the lens.  Nuclear cataracts usually are associated with aging. 
A cortical cataract is characterized by white, wedge-like opacities that start in the periphery of the lens and work their way to the center in a spoke-like fashion.  This type of cataract occurs in the lens cortex, which is the part of the lens that surrounds the central nucleus.  

Cataract Symptoms and Signs:
A cataract starts out small and at first has little effect on your vision.  You may notice that your vision is blurred a little, like looking through a cloudy piece of glass.  Hazy or blurred vision may mean you have a cataract.  A cataract may make light from the sun or a lamp seem too bright or glaring.  Or you may notice when you drive at night that the oncoming headlights cause more glare than before.  Colors may not appear as bright as they once did.  When a nuclear cataract first develops, it can bring about a temporary improvement in your near vision, called "second sight."  Unfortunately, the improved vision is short-lived and will disappear as the cataract worsens.  On the other hand, a subcapsular cataract may not produce any symptoms until it's well-developed. 

What Causes Cataracts?
The lens inside the eye works much like a camera lens, focusing light onto the retina.  It adjusts the eye's focus, letting us see things clearly both up close and far away.  The lens is mostly made of water and protein.  The protein is arranged ins 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, and overtime, it may grow larger and cloud more of the lens, making it harder to see.   

Cataract Treatment
When symptoms begin to appear, you may be able to improve your vision for a while using new glasses, strong bifocals, magnification, appropriate lighting or other visual aids.  Think about surgery when your cataracts have progressed enough to seriously impair your vision and affect your daily life.  Many people consider poor vision an inevitable fact of aging, but cataract surgery is a simple, relatively painless procedure to regain vision.  Cataract surgery is very successful in restoring vision.  In fact, it is the most frequently performed surgery in the United States, with more than 3 million Americans undergoing cataract surgery each year, according to PBA.  Nine out of ten people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40.  During surgery, the surgeon will remove your clouded lens and in most cases replace it with a clear, plastic intraocular lens (IOL).  New IOL's are being developed all the time to make surgery less complicated for surgeons and the lenses more helpful to patients.  Presbyopia-correcting OIL's potentially help you see at all distances, not just one.  Another new type of IOL blocks both ultraviolet and blue light rays, which research indicates may damage the retina.

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