Crystalens® and Accommodation

In Irving, Dallas and Fort Worth, Texas

When you have an intraocular lens (IOL) to correct cataracts or presbyopia, you are receiving a lens that in some way will mimic the behavior of your natural lens, which is removed in this procedure.

There are two types of technology used in making intraocular lenses (IOLs):

• Multifocal; and
• Accommodative

Crystalens® is an accommodative IOL. In contrast, ReSTOR® and ReZoom™ are multifocal IOLs. These are two different ways of achieving clear vision at multiple distances.

What is Accommodation?

The eye’s natural lens changes its curvature automatically when you switch your focus. When you look at something in the distance, it flattens itself, but when you read some small print, it steepens. This is called accommodation. The lens is bending (refracting) light rays so they will focus on the retina and give you clear images, whether the object is near or far.

Any rounded lens will refract light more sharply than a flatter-shaped lens. The cornea is also a lens, and it refracts light entering the eye about 60 percent, with the lens fine-tuning the other 40 percent. But the cornea has a fixed curvature. LASIK improves your eyesight by giving the cornea a different curvature so that it will work in better partnership with the lens.

When the natural lens is removed, accommodation goes with it. That poses the problem of how to provide clear vision at varying distances using an IOL. In past years, IOLs were monofocal, typically providing clear distance vision, with eyeglasses correcting for near vision. But in 2003, the FDA approved the Crystalens for cataract surgery, changing the IOL ballgame.

Crystalens and the Lens Muscles

The curvature of the natural lens is controlled by muscles around it. There are two muscles – one to steepen the curve and one to flatten it. They are called the ciliary muscles. When Dr. Carter places a Crystalens for you, he attaches it to those same muscles. Now instead of the ciliary muscles changing a lens shape, they will be moving the Crystalens slightly forward or back.

• When they move it forward, it is mimicking the lens becoming steeper in shape for near vision
• When they move it back, it mimics the lens becoming flatter for distance vision

You do not feel this happening. It is as automatic as your natural lens changes were and you cannot feel the presence of the Crystalens in your eyes at all. You simply see well at all distances.

Crystalens is the only IOL that works in this way, although there is a second one called Synchrony that is being tested for FDA approval. ReZoom®, ReSTOR™, and Tecnis™ are all multifocal IOLs. They are not connected to the ciliary muscles like Crystalens. Instead they are created with a series of concentric zones or steps that react to light differently. The end result is clear vision at all distances.

If you have presbyopia, an IOL is one way to correct it. Another is LASIK monovision.

If you would like to schedule a free consultation with Dr. Carter, please call or email our office. We offer a wide range of vision correction procedures, as well as optical services, to the residents of Dallas, Texas, and we hope to speak with you soon.