When a cataract is removed, it is replaced with an artificial intraocular lens (IOL). There are a variety of IOLs that can be used in cataract surgery, and they each have their own set of advantages and disadvantages. No single IOL works best for everyone, and only your ophthalmologist can determine the most appropriate IOL for your needs. The FDA approval process for IOLs is among the most rigorous in the world. You can rest assured that any IOLs used in the U.S. have undergone very extensive testing for safety and efficacy. These same IOLs are also used for a refractive surgery procedure known as refractive lens exchange. In refractive lens exchange, the IOL is used solely in an attempt to reduce or eliminate the need for glasses or contact lenses. This article outlines some of the choices of IOLs that are available for use in cataract surgery and refractive lens exchange.
Fixed Focus Monofocal IOLs are used in the majority of cataract procedures. These lenses have the advantage of excellent quality distance vision under a variety of lighting conditions. Since these lenses have a fixed focal point which is generally set for distance vision, reading glasses are typically required for good near vision. For patients willing to use reading glasses for near tasks, these IOLs are an excellent choice. Tens of millions of monofocal IOLs have been used for decades with an excellent safety record. Recent refinements in the optical quality of these lenses have allowed an even higher quality of vision than previously achievable.
Accommodating Monofocal IOLs are used in situations where both good distance and good near vision are desired without the use of spectacles. These IOLs have single focal point, however, the focal point can shift position in space so that objects at distance are clear when the eye focuses on them, but when the eye looks at a near object, the IOL will shift its focal point to bring the near object into focus. Accommodating Monofocal IOLs achieve this by physically moving inside the eye in response to the focusing action of the muscles of the eye. The only FDA approved IOL of this type is called the Crystalens™. Patients implanted with the Crystalens™ IOL generally enjoy near vision without glasses that is much better than a Fixed Focus Monofocal IOL. In fact, results of the FDA trial for the Crystalens™ demonstrated that 98% of patients could see well enough to pass the driver’s test and read a newspaper without glasses. Vision at the intermediate (computer screen) distance is superb with the Crystalens™, making this an excellent IOL for those who spend a great deal of time on a computer.
Multifocal IOLs use a different strategy to achieve good distance and near vision without glasses. These lenses have highly specialized optical properties that can divide light to bring it into focus at more than one point at the same time. This allows the eye to see both near and far, usually without glasses. Excellent results for distance and near vision have been achieved by both of the FDA approved lenses of this type. The ReZoom™ multifocal IOL has several zones of optical power that are designed to provide good vision at varying distances, under varying lighting conditions. In a clinical study, 92% of ReZoom™ IOL patients reported never or only occasionally having to wear glasses. Another multifocal IOL is the ReSTOR™. This IOL uses a patented diffractive optical design to divide light into two focal zones so that near and distance objects can both be seen without glasses. An impressive 80% of patients from the ReSTOR FDA trial reported that they never wore glasses after the procedure. Multifocal IOLs have a slightly greater tendency to cause night vision complaints than other IOLs, so those who drive a great deal at night may wish to consider a different IOL. The vast majority of patients with these IOLs are not bothered by night vision complaints.