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A cataract is formed when the lens in the eye becomes clouded, limiting vision. The lens of the eye is made from protein and water (about 65%). When the proteins clump together, a cataract is formed.  Normally, light  passes through the lens and falls on the retina, forming an image, but if the cataract is formed, the light does not pass through to the retina. Cataract is single largest cause of  blindness worldwide. 

There are different types of cataract - congenital cataract formed in babies, cataract due to eye injury, secondary cataracts formed due to medication and disease like diabetes and due to old age. The cataracts can also be classified according to the method of formation. The nuclear cataract  is formed at the center of  the lens due to aging. Cortical cataract, formed in the lens cortex  and subcapsular cataract formed in the back of  the lens are common in diabetes patients.  About 90% of people older than 65 years have a cataract.

Once a cataract is formed, a surgical procedure is the only way to restore vision. The surgeon will remove the lens with the cataract and replace it with a clear, plastic intraocular lens (IOL). There are 2 surgical procedures used, extra capsular surgery where the lens is removed, but the lens capsule remains and intra capsular surgery where the entire lens capsule is removed.

Phacoemulsification  is a procedure where high frequency sound waves are used to break up the lens before it is extracted for extra capsular surgery. However phacoemulsification cannot be used for treating subcapsular cataract. Intra capsular surgery has to be performed for subcapsular cataract. Some ophthalmologists do not ascertain the type of cataract before calling their patient for surgery, resulting in inconvenience.

Studies show that exposure to ultraviolet rays is associated with cataract formation, so wearing sunglasses is recommended. Smoking and eating salty food also increases the rate of  cataract formation. Eating a diet high in anti-oxidants such as Vitamin A, selenium, Vitamin C and E, may slow down cataract formation.  

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