The new presbyopia treatment, which is undergoing clinical trials in the United States but which has been used for several years in other countries, is called presbyLASIK or multifocal LASIK. The term multifocal is used because the procedure addresses the eyes’ need for multiple focuses in terms of near, intermediate and distance vision.
In a study led by Robert L. Epstein, of the Mercy Center for Corrective Eye Surgery, in McHenry, Ill., 92 percent of middle-aged patients were freed of the need for glasses. In follow-up on the participants, who had an average age of 53 and who came to the study wearing bifocals and reading glasses, the beneficial result was shown to last beyond two years.
Presbyopia is usually corrected with multifocal eyeglasses or contact lenses, which are made with at least three “zones” of power for enhancing sight at all distances. In presbyLASIK, which can also help patients who have had cataract surgery or whose eyes are otherwise inappropriate for LASIK surgery, a laser sculpts three corrective vision zones into the surface of the eye – for far, near and intermediate vision. The patient’s brain then chooses which zone to use for the vision that’s required for a particular task.
In each zone, the sculpted cornea bends light differently, allowing presbyopia sufferers to regain good vision at any distance. This is just how multifocal contact lenses work – but, since they rest on the eye’s surface, they can shift, causing sight distortions.
To date, the Food and Drug Administration has approved only one LASIK procedure for correcting presbyopia. It provides so-called monovision, in which one eye is operated on to improve distance vision, and the other for better near vision. But many people find it difficult to adapt to this arrangement, which can cause problems such as loss of depth perception.