The lens is a structure behind the iris that helps to focus light properly, much like the lens of a camera. A cataract is a clouding of the lens of the eye, usually occurring as a normal aging process.
Over time, cataracts often progress to the point where vision becomes blurred, impairing activities such as driving and reading. No medicine or supplement cures cataracts, and the only way to restore vision to affected patients is to perform cataract surgery.
Each year, over 2 million Americans undergo cataract surgery, making it one of the most common surgical procedures. After decades of innovation, cataract surgery is now performed through a very small incision (three millimeters or less) through which the cataract is removed and a new, clear synthetic lens is placed. By the time most patients require surgery for age-related cataracts, they have already lost their ability to focus at near a condition known as presbyopia. Traditionally, when a new lens in placed after cataract surgery, the goal has been to correct distance vision, with reading glasses required for near or intermediate (computer distance) work. In some cases, these traditional lenses can be used to give near or intermediate vision by correcting one eye for distance and one eye for close-up, known as monovision. With a successful cataract surgery, these lenses can provide outstanding clarity of vision.
Over the past several years, a number of new technology lenses have become available which decrease, and in some cases eliminate the need for reading glasses after cataract surgery. As with everything in medicine, there is no “one-size-fits-all” solution for correcting near and distance vision. Every individual has unique needs based on their lifestyle, occupation and daily activities. For many patients, the traditional “distance correcting” lens is still the best option. Additionally, not everyone is a good candidate for these new presbyopia-correcting intraocular lenses. All of these lenses involve a substantial out-of-cost expense not covered by Medicare or insurance. Generally, these lenses work best when implanted in both eyes. It often takes awhile for the brain to adapt fully to these lenses and allow the maximum near or intermediate vision sometimes six months or longer. Some patients do not adapt fully, and a small number may require refractive laser vision correction (i.e. LASIK) as well to achieve the best possible result. Other patients with certain pre-existing eye disease such as macular degeneration may benefit most from a high-quality monofocal lens.
The three predominant presbyopia-correcting lenses currently available in the US are the ReSTOR lens (Alcon), the ReZoom lens (AMO) and the Crystalens (Bausch & Lomb). Each of these lenses is based on unique technology, and each has its advantages and disadvantages.
The ReSTOR lens uses a series of small steps in the center of the lens which splits incoming light, directing some rays for near and some for distance vision. This lens can be a good option for patients desiring good reading vision, but results are less impressive for intermediate vision (computer distance). The ReZoom lens provides different zones for near and distance vision, and is generally better for intermediate than near vision. The Crystalens works in a different manner; by moving back-and-forth in your eye, it changes your focus from distance to closer similar to the function of the natural lens. While intermediate vision can be very good with the Crystalens, near vision is not as impressive.
A number of modifications can sometimes be used to achieve a wider range of vision with these lenses, including “mixing and matching” different lenses and leaving one eye slightly near-sighted to achieve greater close-up vision. A disadvantage of the ReZoom and ReSTORlens is a greater amount of optical aberrations, including glare and haloes around lights. These disturbances often improve as the brain adapts to the new lens. As not all of the incoming light is directed for one area of focus, the resulting image is slightly less sharp than the image formed by the best monofocal (distance-only) lenses. Though the Crystalens does not have these drawbacks, it can take longer to adapt and gain the full benefit of this lens.
The options for cataract surgery are continuing to evolve, and new intraocular lenses offer the possibility of an improved range of vision. For the right candidates, these lenses have some great advantages. If you have cataracts, ask your ophthalmologist for more information so you can make an informed decision about which lens is right for you.