Crystalens and Accommodating
Intraocular Lenses for
Crystalens (Bausch + Lomb) currently is the only FDA-approved intraocular lens (IOL) that uses a method called accommodation, enabling sharper vision at multiple distances for people who have undergone cataract surgery.
All IOLs for cataract surgery replace the eye's natural lens, which is removed during a procedure. But an accommodating IOL such as the Crystalens shifts position with the action of eye muscles and movement to improve eyesight.
The Crystalens belongs to a select category of high tech intraocular lenses commonly called presbyopia-correcting or "premium" IOLs.
This type of cataract lens may be needed because, beginning at around middle-age, all people lose ability to see at multiple distances due to presbyopia. This condition develops when the eye's natural lens focusing system grows more rigid and no longer can move or change shape sufficiently enough to enable sight at all distances.
If you receive a standard monofocal IOL during your procedure instead of one that corrects presbyopia, you typically would have great distance vision but likely would need reading glasses to sharpen near vision.
More About the Crystalens IOL
You may have heard of the Crystalens, from either news coverage or advertising. The FDA approved the original version of the IOL the Crystalens Model AT-45 in 2003, when it was developed and marketed by eyeonics. The earliest version had a 4.5 mm optic. In 2006, the Crystalens Five-O version with an enlarged 5.0 mm optic was introduced.
Bausch + Lomb acquired Crystalens in early 2008. Then in June of that year, the FDA approved the "HD" or high-definition version of Crystalens.
This version of Crystalens incorporates an improved optic design enabling better near vision, without hampering distance or intermediate vision. Bausch + Lomb officials also say the Crystalens HD is less likely to cause side effects of glare or halos at night. In the U.S. clinical studies involving 125 patients implanted with the Crystalens HD, 80 percent achieved 20/20 or better near vision quality.
In early 2010, Bausch + Lomb introduced another version of the IOL the Crystalens Aspheric Optic (AO). This lens has an elongated shape designed to improve contrast sensitivity and reduce higher order aberrations that can distort vision.
Differences Between Crystalens and Multifocal IOLs
Crystalens is classified as a "premium" or presbyopia-correcting IOL, along with versions of Alcon's AcrySof IQ ReSTOR and Abbott Medical Optics' ReZoom and Tecnis. However, the latter three brands are multifocal IOLs that contain different zones to sharpen vision at multiple distances similar to progressive lenses in eyeglasses.
Multifocal lenses, including those found in IOLs, work because the brain learns to select the appropriate zone to "look" through to provide sight at near, intermediate or far ranges. But because limited space on multifocal IOLs must be divided into zones, some advantages of seeing through just one zone in "single vision" lenses are lost such as better contrast sensitivity.
Research indicates that the Crystalens, because of its design, is less likely than multifocal IOLs to produce visual side effects for distance vision such as night vision problems including glare and halos. At long distance, it is possible that vision may be crisper with accommodating IOLs. However, accommodating IOLs such as the Crystalens may not provide as much of a range of focus (near to far) as multifocal IOLs, and this might lead to the need for reading glasses.
Both multifocal and accommodating types of presbyopia-correcting IOLs have advantages and disadvantages. So you should ask your eye surgeon to clarify which type of presbyopia-correcting IOL, if any, might work best for your particular vision needs.
What You Should Know About Crystalens and Accommodating IOLs
Generally speaking, the best candidates for an accommodating IOL such as Crystalens include people who have both cataracts and hyperopia, which causes near vision problems. Good candidates for this type of lens also include people who had good vision prior to developing presbyopia, which then created the need for reading glasses for near vision.
If you are a perfectionist or hard to please, you likely would not be a good candidate for any kind of presbyopia-correcting IOL.
Crystalens is designed to move within the eye, to provide focusing at all distances. (Animation: Bausch + Lomb)
Cataract surgery outcomes typically are very acceptable. But you also must be prepared for the possibility that something can go wrong with any kind of IOL used in cataract surgery.
Presbyopia-correcting IOLs can provide improved vision, but not perfect vision. And while you could receive at least some benefit of vision at all ranges, a monofocal or standard IOL might be the best choice for crisper distance vision. However, even standard monofocal IOLs also can be associated with night vision problems such as glare and halos.
Cataract and refractive surgeon Robert L. Epstein, MD, also notes that astigmatism can develop late in the healing process after implantation of a Crystalens because of subtle shifting of the IOL's position.
"With the Crystalens in particular, there have been cases of late-change lens position with normal healing creating astigmatism," Dr. Epstein said.
As with any IOL used in cataract surgery, a complication that causes subtle clouding in the lens capsule (posterior capsule opacification) may occur. A procedure called a YAG laser capsulotomy may be needed to clear up the clouding.
"Particularly with the Crystalens, which has optics that depend on position, that YAG laser capsulotomy can cause changes in lens position and therefore in lens performance," Dr. Epstein said.
Before making a decision, you also should weigh your needs against the cost of presbyopia-correcting IOLs that may be as much as $2,500 out-of-pocket per eye.
Investigational Accommodating IOLs
Other IOLS now in testing also use accommodation to enhance vision at multiple distances. Four examples include:
- The Synchrony (Visiogen) is a silicone accommodating IOL that has a two-part optic to help stabilize the lens. The Synchrony is approved in Europe and is undergoing clinical trials for possible FDA approval in the United States.
At a European trade conference, company officials said study results show that the Synchrony produced distance and near vision results similar to a leading multifocal IOL ReSTOR (Alcon) with fewer visual distortions and better intermediate distance vision. (These comparisons involved an earlier version of the ReSTOR IOL, and not the newest version that enhances intermediate vision.)
- The Tetraflex (Lenstec) is an accommodating IOL with a square-edged, acrylic optic. This lens enables sight at multiple distances through changes in thickness that respond to movement of the eye's ciliary muscle. This lens is undergoing late-stage U.S. clinical trials for possible FDA approval.
- The NuLens (NuLens Ltd.) is billed as potentially having the ability to provide up to 10 diopters of accommodation for a wider range of focus, compared to only about two diopters provided by currently approved IOLs. Early research leading to human studies was conducted on primates at the Instituto Oftalmologico de Alicante in Spain.
NuLens has a unique design, which works like a piston. Eye muscles push against a silicone gel lens, which changes shape to provide focus at varying distances.
- As its name suggests, the FluidVision accommodating IOL (PowerVision) uses fluid-based mechanics to change its shape in response to the movement of eye muscles. The lens is in the early stages of human clinical trials, but so far appears capable of providing more than 5 diopters of accommodation.
- The Tek-Clear IOL (Tekia) has been introduced in Germany as a square-edged, accommodating IOL capable of shifting position in response to natural movement of the eye's ciliary muscles.
Again, these five accommodating IOLs have not received FDA approval. At this time, Crystalens is the only presbyopia-correcting IOL available in the United States that corrects vision through the method of accommodation.
In early 2010, Staar Surgical (Monrovia, Calif.) officials announced they were seeking FDA approval of a label change allowing a "premium" designation for the company's single-vision nanoFLEX IOL. Company officials say the IOL's unique design enables clear vision at multiple distances.
Gary Heiting, OD, also contributed to this article.
[Page updated April 2013]
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