Procedures for Presbyopia
Presently, there are several new refractive surgery procedures being developed for the treatment of presbyopia. The market potential for such a treatment is enormous because as we age, we all become presbyopic and lose our ability to focus on objects up close.
Perhaps one of the most promising new procedures under investigation is called PresbyLASIK. A modification of the current LASIK procedure, PresbyLASIK creates a multifocal laser ablation pattern on the cornea, where the central zone of the cornea is steepened for good near vision and the peripheral zone is shaped for good distance vision. (This pattern is similar to the design used in some multifocal contact lenses.)
In a 2005 Canadian study of 33 patients with farsightedness and presbyopia who received the PresbyLASIK treatment, one-third of the patients reported being glasses-free for all reading and about 50% said they wore glasses some of the time to work at the computer. None of the patients needed eyeglasses for day driving, night driving, or any recreational activity.
Additional studies of the PresbyLASIK procedure are currently taking place in the U.S.
Another presbyopia surgery procedure currently in clinical trials is called the PresView Scleral Spacing Procedure (Refocus Group, Inc., Dallas, TX). Research by Refocus Group suggests that as the crystalline lens inside the eye continues to grow with age, it eventually causes overcrowding of the ciliary muscle that surrounds the lens. The ciliary muscle is responsible for changing the shape of the lens so the eye can focus on near objects – a process called accommodation. When the ciliary muscle no longer has enough room to focus the lens, we can no longer see close-up.
In the PresView Scleral Spacing Procedure (SSP), four small plastic segments, each about the size of a grain of rice, are implanted in different quadrants of the sclera (the white outer coating of the eye). These PresVIEW Scleral Implants cause a slight elevation of the sclera, reducing the crowding of the underlying ciliary muscle, restoring its ability to change the shape of the lens for good near vision.
Clinical results of the U.S. Food and Drug Administration (FDA) Phase II investigational study of the PresView SSP were reported in September 2005. About 90% of the patients who received the PresView Scleral Spacing Procedure reported that their close-up vision was either better or significantly better. None of the patients showed any deterioration of uncorrected distance acuity or contrast sensitivity.
In August 2005, Refocus Group received FDA approval to start Phase III clinical trials, which are still ongoing.
Combining Cataract Surgery with Presbyopia Correction
It's also possible to address presbyopia while performing cataract surgery.
Cataract surgery involves removal of the eye's natural, opacified lens. After removal of the lens, refraction must be facilitated with either post-cataract eyeglasses or contact lenses both of which are virtually obsolete or with an implanted artificial lens, called an intraocular lens or IOL.
IOLs have been routinely used for about 30 years. They're appreciated by patients for eliminating their cloudy, cataract-induced vision and restoring the clarity of vision they may not have had for years or decades. But historically, despite their newfound vision, these patients continued to use need bifocals or reading glasses to correct presbyopia.
Now three IOLs are marketed in the United States to correct presbyopia. ReZoom and Tecnis from Abbott Medical Optics and AcrySof ReStor from Alcon are multifocal IOLs that incorporate optics to correct vision at varying distances. And Bausch + Lomb's Crystalens is an accommodating IOL, featuring a lens that moves slightly in response to focusing effort, resulting in improved near and intermediate vision.
Research continues around the globe for new methods to simultaneously address the effects of presbyopia and cataracts.