Multifocal Lenses

Implant Lenses: Monofocal and Enhanced

The young, healthy eye focuses clearly on objects no matter how far or near to the eye those objects are. This is done by the eye muscles pulling on the lens to make the lens change shape to bring the desired image into focus. We generally have three distances that our eyes must accommodate: distance (mountain scenery), intermediate (computer), and near (reading newspaper). As we mature, our lens looses its ability to change shape, so we need glasses to see up close. When we have cataract surgery, our own natural lens is removed and an artificial lens is implanted. The new lens is called an intraocular lens, or, IOL.

“Mono” means “one,” i.e., the wearer gets “one” distance of focused vision, which is usually distance vision. Monofocal lenses focus light to only one point in space. They provide good vision either at distance or near, but not both. It is possible to implant one monofocal lens in one eye for distance and the other monofocal lens in the other eye for near, thereby achieving both near and far vision acuity. This is called “monovision” and is only available to people who are within certain refractive parameters. Most people with monofocal lenses have lenses which are designed for excellent distance acuity, and then wear reading glasses for both near and intermediate acuity. So, with a monofocal lens, one could probably drive a car without glasses. But, to either work on the computer or read a newspaper, most people would need glasses. The monofocal lens used by Dr. Oli is the Tecnis lens, which has been well received.

Multifocal IOL: A multifocal lens tries to mimic natural vision of being able to focus clearly at both distance and near objects. This effect is achieved by putting concentric rings of differing refractive powers into the lens. The different rings of near or far distance refractive powers relay constant images of both near and far. The brain learns to disregard the image that is out of focus. Studies show that most people who choose these new lenses are either glasses-free or much less dependent on glasses or contact lenses. The two available multifocal implants are the ReZoom and the ReSTOR.

Accommodative IOL: While the multifocal sends images of differing focuses from concentric rings, the accommodative lens has continuous points of focus. The lack of concentric rings diminishes the halo effect. The accommodative IOL will “flex” or “accommodate” just as a natural lens would do to deliver a full range of vision. The accommodative IOL is the Crystalens.