Surgery for Presbyopia
Presbyopia is the inability of the eye to focus at all distances, usually noticed when fine print starts to blur.
Some eye doctors disagree about what causes presbyopia. Most believe stiffening of the eye's lens contributes to the condition. Other theories suggest that presbyopia also could be related to continued growth of the lens or atrophy of the muscles controlling the lens.
In the past, the usual remedy was to wear reading glasses or special multifocal lenses (bifocal or progressive lenses) for presbyopia. But in modern times, surgical remedies for presbyopia also are available for qualified candidates.
One of the first effective surgical options for presbyopia correction involved producing what is known as "monovision" during LASIK. But other surgical procedures such as conductive keratoplasty or CK (see below) also have been approved by the FDA, which gives eye surgeons additional options for correcting this common vision problem.
Several other experimental devices and procedures also are under investigation, but not yet FDA-approved. Here is a rundown.
Producing monovision is one way eye care professionals deal with presbyopia. Normally, both your eyes work together equally when you look at an object, to produce what's called binocular vision.
However, you probably have a dominant eye that your brain tends to favor for "sighting" (most right-handed people are right-eye dominant, for example).
Contact lens fitters often take advantage of this "one-eye dominance" to produce monovision, where typically the dominant eye is prescribed a contact lens power for optimum distance vision and the other eye is fit with a contact lens that has a modified power to provide good near vision.
To a large extent, binocular vision is preserved in monovision so you have adequate depth perception for driving, for instance. But one eye sees more clearly in the distance, and the other eye sees better up close.
Some LASIK surgeons will produce monovision in their presbyopic patients by purposely leaving the non-dominant eye slightly nearsighted so that these patients can see up close without glasses. Other surgeons are wary of the technique because not everyone can become accustomed to monovision.
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It's a good idea to try monovision with contact lenses or trial lenses in the doctor's office first to be sure you can adapt to it before you opt for monovision LASIK.
A surgeon performing CK first numbs the eye with drops. A circular treatment pattern then is imprinted in ink on the cornea. This pattern helps guide a tiny probe as radio waves are applied to shrink collagen. The treatment works like a belt to tighten and steepen the curvature of the cornea, resulting in better near vision. (Images: Refractec)
Monovision and Conductive Keratoplasty
Conductive keratoplasty (CK) uses low-level, controlled radio-frequency energy to shrink collagen fibers in the periphery of the cornea. This steepens the central cornea, in effect lengthening a too-short eyeball.
CK was FDA-approved in 2002 for the temporary reduction of farsightedness, then received approval in April 2004 for the temporary improvement of near vision in people with presbyopia.
In a monovision technique called NearVision CK (Refractec), conductive keratoplasty is performed on one eye only usually the non-dominant eye to correct presbyopia in a person who can see well in the distance without glasses or contact lenses, but who needs help with near vision.
Again, it's a good idea to try monovision with contact lenses or a trial lens in the doctor's office before undergoing NearVision CK to make sure you'll adapt to it. After the three-minute procedure, you'll likely notice improvement in your reading vision, but it can take a few weeks before you reach the final level of vision correction.
One attractive feature of CK is that it is minimally invasive. Some people experience tearing, foreign-body sensation and/or vision fluctuation, but this usually is temporary.
A new corneal surgery for the correction of presbyopia, known as IntraCor (Bausch + Lomb Technolas), has shown promising results outside the United States. The IntraCor procedure uses a femtosecond laser to create precisely placed gas bubbles, which then reshape the interior of the cornea without penetrating the outer surface. This means less chance of infection, inflammation or other complications.
Researchers so far report significant improvement in near vision, as long as ample light is provided for tasks such as reading fine print. The technology is approved in Europe for presbyopia correction in people with farsightedness.
Artificial Lenses (Refractive Lens Exchange or RLE)
One currently available option for presbyopia correction involves removing the eye's natural lens and inserting an artificial one in a procedure identical to cataract surgery. While this surgical procedure is not FDA-approved specifically for presbyopia correction, it may be available off-label for qualified candidates.
The surgical procedure, known as refractive lens exchange (RLE) or clear lens extraction, is becoming more popular because of the recent availability of FDA-approved multifocal or accommodating artificial lenses capable of correcting presbyopia.
Multifocal LASIK (PresbyLASIK)
Different zones in a multifocal artificial lens correct vision at near, intermediate and far ranges. In an investigational procedure known as multifocal LASIK or presbyLASIK, similar zones are created on the eye's clear front surface (cornea) with an excimer laser to correct presbyopia.
PresbyLASIK is an investigational procedure, which is not yet FDA-approved. U.S. clinical trials investigating the effectiveness and safety of the procedure currently are being conducted.
Corneal Inlays and Onlays
Corneal inlays and onlays are implantable devices that are surgically inserted just under the superficial layers of the cornea. Because the corneal implants alter the way light enters your eye, near vision is improved.
One corneal inlay currently undergoing FDA clinical trials is the Kamra (AcuFocus and Bausch + Lomb). Formerly known as the ACI 7000, this corneal inlay uses principles similar to how a camera works. In a camera, the aperture opens or closes to control exposure to light and refine focus. When the aperture is small, greater depth of focus is achieved.
In the same way, the Kamra corneal inlay corrects presbyopia by controlling the amount of light that enters your eye and increasing the range of what you see in focus.
Other corneal inlays under investigation include:
- InVue intracorneal microlens (Biovision), which is placed in a tiny tunnel in the center of the cornea.
- Raindrop Near Vision (ReVision Optics), an ultra-thin lens (formerly known as PresbyLens in the U.S. and Vue+ in Europe) implanted in the cornea.
- Flexivue Microlens (Presbia Cooperatief U.A.), which uses a femtosecond laser to create a tiny "pocket" into which the implant is inserted.
Corneal onlays use genetically engineered, collagen-like lens material placed in a pocket under the outer layer of the cornea to achieve better focus. In the future, lasers also may be used to reshape this material to refine focus without altering the eye itself.
Marilyn Haddrill also contributed to this article.
[Page updated February 2014]