Multifocal IOL Implants

Intraocular lenses (IOL) are implantable lenses that are inserted into the eye during cataract surgery or during refractive lens exchange. These lenses are made of plastic or silicone materials and placed permanently in the eye after removal of the eye’s natural lens. Intraocular lenses may be either monofocal or multifocal. Monofocal lenses have a single zone of clear focus, usually set for excellent distance vision, but require the use of reading glasses for near tasks, like reading or sewing. Others, called multifocal lenses, have several zones of clear vision and allow for both distance and near vision correction.

Multifocal IOLs have become increasingly popular among patients because of the likelihood they will no longer be required to wear glasses or contacts after surgery. Multifocal lenses incorporate both distance and near powered lenses into one lens. The lower powered zones bend light coming from distant objects to a single focal point on the retina. The higher powered zones bend light from near objects to the same focal point on the retina. Thus, different zones of lens power work together to provide the eye with near and distance vision.

There are three main multifocal IOL lenses that are currently available for implantation in the eye. The ReZoom™ lens and the ReStor™ lens are two commonly used lenses that work by the multifocal lens principle. Each lens incorporates ring-shaped zones of differing optical power to provide a multifocal effect. A third lens, the Crystalens™, works in a different manner to provide a multifocal effect. By moving forward in back of the eye on small hinges, the lens can change its power in the eye, similar to the process of accommodation of the eye’s natural lens. Hence, the Crystalens™ is called an accommodating lens, and can provide both near and distance focus.

The main advantage offered by multifocal lenses is the opportunity to become less dependent on reading glasses for near activities. For many people, presbyopia, the loss of the eye’s ability to zoom from distant to near objects, is very frustrating and becomes worse with age. For people frustrated by the need for reading glasses, multifocal lenses offer a good alternative. For example, in the FDA trial of the ReStor™ multifocal lens, 84% of ReStor™ patients achieved simultaneous 20/25 distance vision, which is a single line away from perfect 20/20 vision, and near vision which allowed newsprint to be easily read. However, only 23% of patients with monofocal IOL lenses in the same study were able to achieve those levels of distance and near vision simultaneous. The clinical trials for the ReZoom™ multifocal IOL and Crystalens™ accommodating IOL also demonstrated markedly better simultaneous near and distance vision with these lenses compared to traditional monofocal IOLs.

The trade-off for simultaneous distance and near vision with multifocal lenses is a higher amount of aberrations produced by the lenses multifocal optics. Typically, these aberrations are perceived as a glare in certain low lighting situations and halos around light sources at night. Most people with multifocal lenses find these aberrations to be only minor. Over time, the brain tends to adapt to them. Additionally, multifocal lenses usually need to be implanted in both eyes before full adaptation can occur. Also, since the optics of these lenses split the light, the image formed on the retina is slightly less perfect than that which can be formed by a monofocal IOL. Hence, a small amount of image quality may also be sacrificed to gain the multifocal effect. The vast majority of people with multifocal implants are very happy with them and would chose to have them placed again. However, a small minority of patients do not adapt to the lenses well or are very bothered by the glare and halos that can occur with them. Dr. Gipson will go over the pros and cons of each type of multifocal lens with you to help find the one must suitable for your eyes.