Derived from the Greek words for aging eye, presbyopia refers to age-related refractive changes in the eye that occur when the lens of the eye (which focuses light on the retina) hardens and loses elasticity.
As presbyopia develops, typically starting at age 40, focusing on objects that are up close becomes increasingly difficult —and so people with presbyopia typically reposition reading material in an effort to see it clearly. Eventually, most older adults need reading glasses to bring near objects into focus.
Although there is no way to restore the elasticity of the lens, carefully calibrated changes in the cornea can compensate. But until now, the only alternative to reading glasses for people with presbyopia has been an off-label use of excimer laser surgery, or LASIK, that corrects one eye for close vision and adjusts the other eye for distance vision, a technique known as monovision.
Although this approach can work well for presbyopia, the LASIK procedure requires cutting a flap in the cornea (the transparent front window of the eyeball) and may sometimes lead to dry eye and other potential complications.
Recently, the Food and Drug Administration (FDA) approved a technique called conductive keratoplasty (CK), a minimally invasive procedure that does not pose the problems related to the LASIK flap.
CK appears to be a relatively safe and effective treatment to cope with presbyopia, but there are several caveats for anyone considering the procedure if you have presbyopia. Many people with presbyopia are not candidates for CK; the procedure may have to be repeated in a few years because the corrective effect is not permanent; and complications, though rare, can occur.
Who Is a Candidate for CK?
CK is suitable for people over 40 who presbyopia, have had relatively good distance vision most of their lives, and do not have eye diseases. People who are nearsighted (myopic) or very farsighted (hyperopic to an extent greater than +3 diopters) are not good candidates. Because CK employs radio waves that may interfere with the operation of electronic equipment, anyone wearing a pacemaker should not undergo this procedure.
According to Terrence O’Brien, M.D., Director of Refractive Eye Surgery at Johns Hopkins, “People older than 55 are not necessarily good candidates for CK because they may be developing cataracts and because their aging corneas may not respond in quite the same way as those in the 45- to 55-year-old group.” In addition, people who have astigmatism (an asymmetric curvature of the cornea that can affect vision), he notes, “would be far better off undergoing LASIK, which can treat both astigmatism and farsightedness simultaneously.”
Somebody who has already had LASIK to correct farsightedness could later undergo CK for coping with presbyopia. But, according to Dr. O’Brien, “it’s usually easier to just lift the flap on the cornea and apply more of the excimer laser treatment to achieve the same effect.”
How CK Is Done
In CK, an ophthalmic surgeon uses a tiny, hair-thin probe to apply radio waves to the outer cornea in a circular pattern. The radio waves shrink small areas of collagen to create a constrictive band that increases the overall curvature of the cornea, thereby improving near vision. CK is performed using a topical anesthetic in a doctor’s office or clinic. People can usually return to work or their normal activities the day after the procedure.
CK is generally performed in one eye only—usually the nondominant eye—to improve close-up vision. The other eye, which is left untouched, provides most of the distance vision. The effect is similar to the monovision achieved by LASIK for presbyopia. Some people adapt well to monovision, while others do not.
“Usually, before patients undergo CK, we suggest they get the feel of monovision by using a contact lens to simulate slight nearsightedness in one eye,” Dr. O’Brien comments. “If they say, ‘Oh, this is just fabulous,’ we know they’ll be a good candidate for CK. But not everybody can adapt to monovision.”
Most presbyopia patients notice improvement in their near vision immediately, but it usually takes several weeks for the eyes to reach their final level of vision correction. After one year of follow-up, according to clinical data submitted to the FDA during the approval process, 98% of patients who had undergone CK could read newspaper-sized print unaided with the treated eye.
Other Factors to Consider before CK Is Performed
- Durability. Experts estimate that many patients will require retreatment after about 3 to 5 years to restore the initial correction. Dr. O’Brien says, “A problem with CK is that the heat that shrinks the corneal collagen can sometimes induce a temporary effect. As the aging of the eye continues, the corneal collagen relaxes and the corrective effect weakens over time.”
- Potential complications of CK. Thus far, there have been no reports of serious, sight-threatening complications. Some presbyopia patients may initially experience such problems as double images, halos, blurry vision, and a slight overcorrection of their near vision after the procedure, but these side effects typically disappear in several weeks. In a small percentage of patients, the procedure has induced astigmatism. Many patients experience some loss of depth perception after CK.
Dr. O’Brien observes, “CK can work very well for the patient who has been properly selected, but it is not the miracle cure for presbyopia. It does not lead to a return of the dynamic ability to focus at near distances. Much like excimer laser surgery, it creates monovision to allow some improved performance without the need for reading glasses.”
- Precautions after CK. Patients will have to apply antibiotic eyedrops for a week after the procedure to reduce the chance of infection. In addition, for 1 week after undergoing CK, all patients must avoid getting contaminated water (such as water from swimming pools, lakes, or spas), soap, or sweat in their eyes, and women must avoid applying eye makeup. It is also recommended that patients avoid rubbing their eyes for 2 weeks following the procedure.
- Cost. CK typically costs about $1,500, and the expense is not covered by medical insurance because CK is considered a cosmetic procedure.
For more Vision articles,
please visit the
Vision Topic Page
Posted in Vision on February 7, 2006
Reviewed May 2007
