CATARACTS -- New lens implants to reduce your dependence on glasses
General information about cataracts, symptoms, causes, and treatment, can be found in the "cataract" section under the Disorders menu above.
Cataract surgery is a once-in-a-lifetime opportunity to become less dependent, and possibly independent, of glasses. This can happen because the lens implanted at the time of surgery can act like your glasses or contact lens correction, leaving you with better vision without glasses than you had before surgery.
Read below to better understand:
- What is different about these lens implants
- The 4 basic refractive errors, and how they blur vision
- How the Toric Acysof lens reduces astigmatism
- How the Multifocal lenses reduce presbyopia
What is different about these lenses?
Doctors have been implanting intraocular lenses at the time of cataract surgery for decades. In the past, traditional lens implants could only correct for myopia or hyperopia. In most patients who also have astigmatism and presbyopia, the traditional lenses still left patients dependent on glasses at least part time. However, newer lens implants can correct astigmatism and presbyopia, thereby greatly reducing ones dependence on glasses. The cost of these newer lenses are not covered by insurance, although the cataract surgery itself is covered. For more information about the additional fees, read here.
The 4 basic refractive errors:
Refractive errors are simply the eye's errors of focusing, which cause blurry vision. As the video above illustrates, the two structures in our eye that are responsible for focusing light are the cornea (the clear window in front of the eye where a contact lens would rest) and the lens (where cataracts form, located just behind the iris). If the cornea and lens focus well, images are clear on the back of the eye on the macula. The macula is the center of the retina, acting like the film in a camera, taking a picture to send back to the brain. When the cornea and lens are not focusing light on the macula, there will be blurry vision from one or more refractive errors.
Mypopia: Also called nearsightedness, myopia occurs when light is focused in front of the retina. Nearsighted people noticed that near objects are in better focus than distance objects. The eye has too much focusing power. A traditional lens implant with spherical correction can reduce the lens power, thereby improving distance vision. If someone with myopia has good near vision without glasses, a lens implant that reduces myopia may worsen near vision as it improves distance vision.
Hyperopia: Also called farsightedness, hyperopia occurs when light is focused behind the retina. People who are farsighted usually notice blurry vision at all distances, but objects in the distance are in better focus than those at near. The eye has too little focusing power. Traditional lens implants with spherical correction can increase the lens power, thereby improving distance vision. However, near vision will still be blurry.
Astigmatism: Astigmatism occurs when the eye has more than one curvature, like a football compared to a basketball. Light is focused at different distances, resulting in blurry vision. Traditional lens implants are spherical, so cannot correct astigmatism. New lens implants that have a football shaped surface (called a "toric" surface) can reduce or eliminate astigmatism, making vision clearer. These are called toric lens implants, and are shown below.
Presbyopia: This occurs when the eye can't focus from distance to near. This is a normal event that usually becomes apparent in our 40's and worsens over time. Traditional lens implants have just one focal length. They give the eye a single focus, so cannot correct presbyopia. New lenses can reduce or eliminate presbyopia. They are called multifocal intraocular lens implants (such as the Tecnis multifocal, or ReStore Acrysof), or accomodative lens implants (like the Crystalens). Multifocal lenses cannot correct astigmatism, which if present, needs to be corrected by other means, like LASIK or PRK. Multifocal lenses are shown below.
Toric Intraocular Lenses for Astigmatism: AcrySof
By reducing astigmatism, these lenses will make vision without glasses clearer. When implanted, the steep axis (marked by the parallel notches) is aligned with your astigmatism. There are three different strenths of this lens to choose from depending on how much astigmatism is present. The goal is to reduce your dependence on glasses. The cost of these lenses is not covered by insurance, however the surgical procedure itself is covered (read more about the costs).
As is often the case after cataract surgery, residual refractive errors may still require glasses correction for best vision. This lens doesn't treat presbyopia, so at least part time glasses wear for reading could be anticipated.
Toric lens implants carry many of the same risks of traditional spherical lens implants. One additional risk is postoperative lens rotation, which fortunately is quite rare. If that were to occur, the axis would be wrong, decreasing the effectiveness of the lens. A return to the operating room for lens repositioning usually corrects the problem.
Multifocal Intraocular Lenses for Presbyopia: ReSTOR and ReZoom
These lenses have rings of different focal length that focus light at different distances. Some light passing through the lens is focused for distance and some for near. In that way, both distance and near objections are in focus. These lenses work best when implanted in both eyes.
As noted above, these lenses are not covered by insurance, although the surgery itself is covered (read more about fees).
Most individuals (over 90%) implanted with these lenses in both eyes report no need for glasses. However, some people may still need glasses part time for certain distance or near activities. There is also a learning curve, called "neuroadaptation," to get used to the new lenses. Neuroadaptation takes a few weeks to months, during which time, near vision may not be as clear.
For these lenses to work well, only small residual refractive errors should be present. For example, these lenses cannot treat astigmatism. If there is significant astigmatism or other residual refractive errors, a second surgery will be planned, like laser refractive surgery (read about LASIK / PRK), or a Limbal Relaxing Incision.
Multifocal lenses have possible side effects and risks. These are in addition to the risks of cataract surgery itself. Because of the rings, haloes are always noticed at night initially. Fortunately most glare resolves or becomes less noticeable over several weeks to months. A small number of people report bothersome nighttime glare that does not go away. About 0.3% of patients will request the lens be removed because of bothersome glare and haloes. Another possible side effect is decreased contrast sensitivity, which is the ability to see in dim light, such as at dusk or in the fog. If there are residual refractive errors, further surgery will be necessary, including additional fees.
Not every patient is a good candidate for multifocal lenses. Certain eye conditions, such as macular degeneration, may decrease the success rate. Multifocal lenses will not work for very detailed near work closer than 13 inches or so. Patients in occupations that require excellent night vision or contrast sensitivity may not be good candidates. Your surgeon will be able to counsel you regarding the above.
Click here to visit the ReSTOR company website and read more about this lens
Click here to visit the Tecnis company website and read more about this lens