PresbyLASIK (Multifocal LASIK,
Bifocal LASIK or LASIK for
Currently undergoing U.S. clinical trials, the procedure has been performed in other countries for the past several years, with promising results.
While it's unclear when FDA approval may occur, multifocal LASIK eventually could be a new option in the United States for correcting presbyopia, which causes near vision to blur as the eye's natural lens begins to lose its focusing flexibility.
No one escapes presbyopia, which begins to show up at about age 40. Solutions for presbyopia include multifocal eyeglasses, multifocal contact lenses, artificial lenses (IOLs for cataract surgery) and now, multifocal LASIK eye surgery.
How Multifocal LASIK Works
Multifocal LASIK creates more than one power on the front surface of the eye, which lets you see simultaneously through different zones providing near, intermediate and distance vision.
If you are middle-aged or older and don't have multifocal vision correction, typically you can see clearly at only one distance, such as far.
Many people in this age group need reading glasses or a special "add" in power to create a near reading zone in the glasses they wear ordinarily. These types of glasses are called bifocals. In recent years, an additional zone providing intermediate vision led to creation of trifocals.
Sophisticated technology now enables multiple or progressive zones to be incorporated into artificial lenses to enable "multifocality" or sight at all distances. In the same way, multifocal LASIK provides similar zones by reshaping your eye's clear surface into precise contours that alter the way light rays enter your eye to achieve focus.
Conventional LASIK procedures reshape the eye's surface so that your eyes focus better at near or far ranges, depending on whether you are farsighted or nearsighted. But as your eye ages, it loses flexibility.
You no longer can see clearly at all distances simultaneously, even if you do wear conventional glasses or contact lenses or already have had LASIK for a problem like nearsightedness.
For presbyopic eyes, the only currently available FDA-approved LASIK procedure provides monovision. This means one eye is corrected for better distance vision, and the other eye is corrected to enhance near vision. Many people cannot adapt to this kind of sight, which can cause problems such as loss of depth perception.
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Unlike monovision, multifocal LASIK corrects presbyopia like this:
- An excimer laser reshapes your cornea into different zones for near, far and intermediate vision. Your brain then selects which zone it needs to see through to get the sharpest vision, depending on whether an object is near or far away.
- In each zone, light is bent or refracted differently, allowing people with presbyopia to regain good vision at all distances similar to how multifocal contact lenses correct presbyopia.
However, multifocal contact lenses resting on the surface of any eye can move and cause vision distortions. Multifocal LASIK, on the other hand, provides fixed, stationary zones directly on the eye's surface.
Just as multifocal contact lenses and other artificial lenses have different designs, various approaches are used in multifocal LASIK to determine exactly how the cornea should be shaped to achieve the best correction for presbyopia.
PresbyLASIK With Distance Vision in the Center
Refractive surgeon Robert L. Epstein, MD, director of the Mercy Center for Corrective Eye Surgery near Chicago, prefers a central zone for distance vision in presbyLASIK.
"I chose this approach because of the possibility of easy reversibility to pure monofocal distance correction, should it be needed," said Dr. Epstein, who is participating in U.S. clinical trials. "I felt this was safer than the opposite approach, where the peripheral cornea is corrected for distance and the center for near."
Dr. Epstein's approach is similar to that of French refractive surgeon Alain Telandro, MD. Dr. Telandro has developed a multifocal ablation software program called Pseudo-Accommodative Cornea (PAC) and has trained surgeons in many countries to perform the procedure. He estimates that more than 10,000 people have undergone the PAC multifocal LASIK procedure.
Since its introduction in 2004, the distance-center PAC procedure has been revised and improved several times. Dr. Telandro estimates that 80 to 85 percent of current patients are pleased with the results, and only about 10 percent of patients need a second "enhancement" treatment.
Dr. Telandro also says the PAC multifocal LASIK treatment provides good intermediate vision as well as good distance and near vision, letting you work comfortably at a computer without reading glasses or other corrective eyewear.
PresbyLASIK With Near Vision in the Center
Jorge L. Alio, MD, PhD, professor of ophthalmology at Instituto Oftalmologico de Alicante in Alicante, Spain, prefers a multifocal ablation with the center of the cornea shaped for near vision, surrounded by a peripheral zone for distance vision.
Dr. Alio says this approach enables the surgeon to provide a stronger correction for reading and other near vision tasks. He also believes that the near-center approach causes fewer aberrations than distance-center ablations. For both reasons, Dr. Alio believes near-center multifocal LASIK provides greater freedom from reading glasses than distance-center approaches.
Customized PresbyLASIK Based on Design or Refractive Error
The best multifocal LASIK design for you also may depend on what kind of vision error you have, in addition to presbyopia.
Gustavo Tamayo, MD, director of the Bogota Laser Refractive Institute in Colombia, has been performing multifocal LASIK since 2000. He has designed a multifocal ablation profile now in clinical trials sponsored by Abbott Medical Optics (AMO, formerly Advanced Medical Optics). Dr. Tamayo and AMO are investigating a distance-center multifocal LASIK profile for myopic patients with distance vision problems, and a near-center approach for hyperopes with near vision problems.
PresbyLASIK With Modified Monovision
With this approach using presbyLASIK in one eye only, you still may need reading glasses, though to a lesser extent. You also may have sharper distance vision with modified monovision, compared with undergoing multifocal LASIK in both eyes.
If you opt for modified monovision, depth perception at most distances is unimpaired, although some problems have been reported at distances of about a foot or nearer. So if you are a carpenter or a dentist, you should have no trouble adapting to this type of vision in most instances.
The most common symptom associated with modified monovision has been slight distance blur. This is because the presbyLASIK eye is corrected to be slightly myopic so that you have better near vision.
Dr. Epstein said strong distance vision is essential with LASIK of any kind. So he favors the modified monovision approach of using presbyLASIK in one eye and wavefront-guided (custom) LASIK in the dominant eye. He has used this method in investigational presbyLASIK procedures since 2003.
"We just cannot match what monofocal wavefront-guided LASIK provides for good distance vision," he said.
He said tolerance for modified monovision easily can be tested before a procedure is done. Whereas straight monovision typically provides only two focal points (near and far), modified monovision with multifocal LASIK adds a third, intermediate focal point that otherwise would be unobtainable with monovision.
"This gives vision over a broad range of distances," he explained. "It's also much easier to adapt to the milder difference in correction in the eyes when we use presbyLASIK in the non-dominant eye and wavefront-guided distance LASIK in the dominant eye."
Dr. Epstein said the presbyLASIK eye in modified monovision also can be "tuned" to emphasize distance vision and leave intermediate vision unchanged. This means near vision is slightly reduced, but far vision is corrected in the presbyLASIK eye to about 20/30 at distance to assist people who have occupations and interests such as commercial driving, heavy equipment operation or motorcycle riding.
Can PresbyLASIK Be Reversed?
The ability to "reverse" a procedure if it doesn't work out also is being tested in clinical trials and will be a major factor in FDA considerations that could lead to approval of presbyLASIK.
"It turns out that we have almost never needed to reverse the presbyLASIK eye," Dr. Epstein said. "Only one patient has had a reversal by request. And we intentionally reversed presbyLASIK in a patient who was getting a cataract years after LASIK, so that she could have a multifocal lens implant instead."
Dr. Epstein said refractive surgeons have found it more difficult to reverse presbyLASIK with a central zone designated for near vision than for a central zone designated for distance vision.
How Effective Is Multifocal LASIK?
A number of multifocal LASIK clinical studies show promising early results:
- In a Canadian study reported at the 2006 American Academy of Ophthalmology conference by W. Bruce Jackson, MD, 49 farsighted and presbyopic patients were involved, and 82 eyes were treated. One year after surgery, all patients were able to see 20/25 or better in the distance and at a level of "J3" (ability to read newspaper print) or better at near.
- In a study published in the May 2008 issue of Journal of Refractive Surgery, 44 eyes of 22 mildly farsighted patients with presbyopia were treated with a distance-center peripheral multifocal LASIK (PML) ablation. Six months after surgery, the mean binocular (both eyes) uncorrected visual acuity (UCVA) in the distance was 20/20, and the mean binocular UCVA up close was approximately 20/25.
- In another 2008 study published in the Journal of Refractive Surgery, Dr. Epstein found that, about two years after having monofocal distance LASIK in the dominant eye and presbyLASIK in the non-dominant eye, 91 percent of 103 myopic and hyperopic patients reported being completely free of eyeglasses. The average age of patients was 53, and all were wearing bifocals or reading glasses prior to the procedure.
If your vision was normal except for presbyopia prior to multifocal LASIK, it's possible your distance vision may be blurry immediately after the surgery. This problem may not necessarily go away, either. It's also possible you'll experience reduced contrast sensitivity and/or a tendency to see halos around lights at night.
Reduced contrast sensitivity means difficulty seeing objects against backgrounds of similar colors. But some research indicates that reduced contrast sensitivity associated with multifocal LASIK may be only temporary and tends to disappear in three to six months.
If you develop cataracts after multifocal LASIK surgery, you will still be able to have cataract surgery. But changes made to your cornea during the LASIK procedure make it a bit more challenging for your cataract surgeon to determine the correct power for your intraocular lens to give you a perfect visual outcome after cataract surgery.
It's possible you may need to wear eyeglasses after cataract surgery or you may need additional corneal refractive surgery to regain acceptable vision for driving and/or reading without glasses.
Finally, there is no guarantee that results of your multifocal LASIK surgery will be permanent. If your eyes change as the years go by after your LASIK surgery, future surgical enhancements may be needed. Another possible complication associated with the procedure can include an inability to see as well as you once did, even with the help of glasses or contact lenses after surgery.
Correction of presbyopia in hyperopia with a center-distance, paracentral-near technique using the Technolas 217z platform. Journal of Refractive Surgery. May 2008.
Presbyopia treatment of monocular peripheral presbyLASIK. Journal of Refractive Surgery. July 2008.
Marilyn Haddrill also contributed to this article.
About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.
[Page updated March 2014]
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