subject: Using an IOL in Cataract Surgery [print this page] Using an IOL in Cataract Surgery Using an IOL in Cataract Surgery
If you or a loved one has been diagnosed with cataracts, you know that something must be done. Cataracts are a progressive clouding-up of the eye's lens, making your eyesight dimmer as the years pass. There is no way to treat cataracts except by removing the lens and replacing it with an artificial lens.
If cataracts are not treated at all, they will become worse and eventually cause total blindness. They are one of the world's leading causes of blindness because so many countries cannot provide cataract surgery for everyone who needs it.
Until 2003, there was only one kind of artificial lens that could treat cataracts and it was monofocal. In other words, it gave clear vision only for a predetermined distance range, usually near distances. For far distance, the person had to wear glasses. In some cases it was the other way around, depending on your lifestyle.
A New IOL Crystalens
In 2003, the FDA approved an intraocular lens (IOL) called the Crystalens. It is an accommodative IOL. What does that mean? Well, when your eye surgeon places it in the eye, he or she connects it to the same muscles that previously controlled your natural lens curvature. With the natural lens, that automatic change of shape is called Accommodation and it is lost when the lens is removed to treat cataracts. Without the natural lens, the eye cannot adjust for how far away objects are and cannot give you a clear image of objects at every distance, the way a normal eye can.
When a Crystalens IOL is substituted for the natural lens, those muscles do not change its curvature, but instead, they move it slightly forward for near vision and slightly back for far vision. This movement mimics what used to happen when the muscles made the natural lens steeper for near vision and flatter for far vision. It happens automatically without you feeling it. The original Crystalens has been improved several times and most currently has a version called Crystalens HD.
Multifocal IOLs
A Crystalens is constructed with only one focus and it is the movement that allows a change of focus. There are other IOLs that are not attached to the lens muscles, but have zones or areas that each provide a different focus and together they give clear vision at all distances.
One is The AcrySof ReSTOR IOL. It uses apodized diffractive technology that has been used for many years in microscopes and telescopes for improved image quality. A ReSTOR IOL is made with concentric steps from the center to the periphery. The word "apodized" means "stepped" and diffraction is the scattering of light. The IOL center area diffracts light outwards to the next several steps. The outermost step is refractive instead of diffractive and focuses light towards the retina. Working together, all the areas give clear vision at all distances.
Another multifocal lens is the Tecnis IOL, which received FDA approval in 2005. Its construction, unlike all other IOLs, is based on Wavefront data the same Wavefront data that is used in the diagnosis for Custom LASIK (also called Wavefront-Guided LASIK). Wavefront diagnosis detects far more of your vision status than just myopia, hyperopia and astigmatism, the three Lower Order Aberrations.
It also detects what are called the Higher Order Aberrations, most of which relate to night vision. Examples are halos or starburst shapes around light sources, and ghosting (faint duplicate images). Both Custom LASIK and the Tecnis IOL give better night vision. Tecnis also corrects astigmatism.
Your eye surgeon will explain how the different IOLs work and why one might be a better choice in your case than the others to treat your cataracts.
