As with all LASIK procedures, the patient's eyes are first examined thoroughly for any condition that might prevent surgery or hinder its effectiveness before subjecting the cornea to laser ablation. In many cases a Wavefront exam is performed to precisely map the patient's eyes and create a detailed guide for the surgeon to use in creating the multi-focal corneal zones needed to correct for presbyopia.

The surgeon then uses an Excimer laser to reshape the cornea into different zones for near, far and intermediate vision. After surgery, the brain then selects which zone it needs to see through to obtain the clearest vision, depending on whether an object is near or far away.

Because light is bent or refracted differently in each zone of the cornea, PresbyLASIK allows patients with presbyopia to regain optimum vision at all distances -- similar to the way multi-focal contact lenses correct for presbyopia. However, because multi-focal contact lenses resting on the surface of the eye can move and cause distorted vision, many patients are dissatisfied using contact lenses in the long run. PresbyLASIK, on the other hand, creates fixed, stationary zones directly on the surface of the cornea.

Just as multi-focal contact lenses and other artificial lenses are offered with different designs, a number of different approaches are used in multi-focal LASIK treatment to determine exactly how the cornea should be shaped to achieve the best correction for presbyopia.

Some surgeons believe multi-focal correction is optimized when the central part of the cornea is dedicated to distance vision with the surrounding corneal tissue being shaped for intermediate and near vision.

Other surgeons prefer to shape the central cornea for good near vision and designate the surrounding zone for distance and intermediate vision. Patients should discuss the pros and cons of each approach with their surgeon to determine which may be right for them.

Multi-focal LASIK typically is performed on both eyes, but also can be applied only to the non-dominant eye for a "modified monovision" correction. The other eye would then be treated with LASIK distance correction only if necessary.