An intraocular lens (IOL) works in much the same way as the eye's crystalline lens: it focuses light onto the back of the eye (the retina). The retina converts the light rays into electrical impulses that travel through the optic nerve to the brain, where they are then converted into images.

If the light isn't focused correctly on the retina, the brain can't "see" the images correctly.

The most common type of IOL is called a posterior chamber lens, meaning it is placed behind the iris within the lens capsule where the natural lens used to be. When it is placed in front of the iris, as might happen when the lens capsule is damaged, it is called an anterior chamber lens. In either case, small arms (haptics) extending from the lens help hold it in place.

A standard, or monofocal, IOL provides a set focal point, usually for distance vision. This allows cataract surgery patients to see clearly within a range. About 95 percent of people who receive a standard IOL have their vision restored to its pre-cataract state.(1) But most patients still require glasses for reading or distance vision.

An accommodative lens is a monofocal lens as well, but this IOL is designed to move in response to your eye's own muscles. When you look at something far away, the muscles in your eye relax and may cause the lens to move slightly backward and assume a flat position. When you shift your gaze to something up close, the muscles contract, which may move the lens slightly forward and cause the lens to become more curved.

A multifocal lens includes corrections for near, intermediate and distance vision in the same lens. This is made possible through highly specialized optics that divide light and focus it on more than one point to provide a range from near to distant. Because of the multifocal lens's ability to focus light on more than one point, multifocal lenses have proven to greatly reduce dependence on glasses.

Toric lenses are designed to neutralize astigmatism, reducing or eliminating the need for distance glasses. These lenses may also eliminate, in many cases, the need for limbal relaxing incisions, a technique where incisions are made at the edge of the cornea to cause it to heal in a more spherical shape.