A cataract is a clouding of the eye’s natural lens, which lies behind the iris and the pupil. The lens works much like a camera lens, focusing light onto the retina at the back of the eye. The lens also 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 in a precise way that keeps the lens clear and let’s light passes 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 over time, it may grow larger and cloud more of the lens, making it harder to see.

Cataracts are classified as one of three types; a sub capsular cataract begins at the back of the lens. People with diabetes, high farsightedness or retinitis pigmentosa, or those taking high doses of steroids, may develop a sub capsular cataract. 

A nuclear cataract is most commonly seen as it forms. This cataract forms in the nucleus, the center of the lens, and is due to natural aging changes.

A cortical cataract, which forms in the lens cortex, gradually extends its spokes from the outside of the lens to the center. Many diabetics develop cortical cataracts.
How it presents

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 or viewing an impressionist painting.

A cataract may make light from the sun or a lamp seems 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.
The type of cataract you have will affect exactly which symptoms you experience and how soon they will occur.

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 sub capsular cataract may not produce any symptoms until it’s well-developed.

If you think you have a cataract, see an eye doctor for an exam to find out for sure.

Causes

No one knows for sure why the eye’s lens changes as we age, forming cataracts. Exposure to ultraviolet light is associated with cataract development, so eye care practitioners recommend wearing sunglasses and a wide-brimmed hat to reduce your exposure.

Some eye care practitioners believe that a diet high in antioxidants, such as beta-carotene (vitamin A), selenium and vitamins C and E, may forestall cataract development. Meanwhile, eating a lot of salt may increase your risk.

Other risk factors include cigarette smoke, air pollution and heavy alcohol consumption.

Treatment

Cataract surgery is very successful in restoring vision.

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