Artifical lenses for the treatment of cataract, commonly called IOLs, (Intra ocular lenses) are tiny prescription lenses, used to replace the eye's natural lens when it becomes clouded because of a cataract. 
 

An IOL is inserted in the eye

There are two basic types of IOLs:

• Foldable  IOLs
• Hard IOLs

 
Foldable IOLs are made of silicone or acrylic  material and can be folded and placed inside a tiny tube. The tube is inserted through a very small incision. Once inside the eye, the IOL unfolds. Because of this small incision the eye will recover fast.
 
Hard plastic lenses are used in certain circumstances determined by the surgeon. Since they cannot be folded, they are inserted through a slightly larger incision.
 
The IOL may be one of the most important ophthalmic developments in the past 30 years. Before the development of IOLs, cataract patients were forced to wear thick glasses or contact lenses after the surgery because the natural lens was removed but was not replaced by anything. They saw next to nothing. They were legally blind without their thick glasses. Today, patients receiving IOLs often enjoy an excellent vision for the rest of their life. Thanks to the corrective prescription power of the lens, the IOL not only replaces the need for thick glasses, it can also correct the eye’s existing refractive error.