PresbyLASIK (Multifocal LASIK, Bifocal LASIK Or LASIK For Presbyopia)
Multifocal LASIK (presbyLASIK) is an advanced type of laser vision correction surgery that changes the shape of the eye’s cornea to create different power zones for seeing at varying distances.
If you are nearsighted and have presbyopia, you may be able to see up close without your usualeyeglasses or contact lenses but not when you are wearing them.
No one escapes presbyopia, which begins to show up at about age 40. Solutions for presbyopia includemultifocal 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 glassesor 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 orprogressive 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.
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.
(Excerpts from an article published at http://www.allaboutvision.com/visionsurgery/presby-lasik.htm)