Article Date: 6/1/2003

refractive
Presbyopia Surgical Options
New procedures involving LASIK, conductive keratoplasty and IOLs could mean that presbyopia's days are numbered.
BY MARC BLOOMENSTEIN, O.D., F.A.A.O.

ILLUSTRATION BY JOEL AND SHARON HARRIS

I used to joke that if I found the cure for the common cold, I would retire richer than I could imagine. However, as the years catch up with me (and my patients), I think that there's no cure more lucrative than one to reverse presbyopia. We've all heard the statistics regarding baby boomers and presbyopia and they are staggering -- even more staggering is the reality that no one is immune to the disorder.

However, researchers are making strides; procedures are already being performed that improve our presbyopic lives. In the very near future, some surgical options may even reverse presbyopia. Following are the up-and-coming solutions.

Competition for monovision

Currently we use monovision as a way to "cheat" the lack of accommodation. Unfortunately, this isn't always successful; most problematic is the lack of binocularity and the compromise that patients must endure. Refractive surgeons have successfully used lens replacement and hyperopic laser-assisted stromal in-situ kerato-mileusis to accomplish this goal.

More recently, the U.S. Food and Drug Administration approved conductive keratoplasty (CK) to treat upwards of 3.00D of hyperopia. Refractec, which markets the CK system, contends that this is a safer alternative to LASIK. CK works by placing eight to 32 thermal injections into the peripheral cornea, thus preserving the central cornea. This outpatient procedure, performed with a topical anesthetic, heats the stromal tissue in a column that tightens circumferentially, steepening the central cornea.

C&C Vision's CrystaLens (L) and HumanOptics' Akkommodative 1CU (R) both claim to restore accommodation. 

Side effects of induced cylinder, pain, and the need to repeat the procedure have been reported. Moreover, in a recent study, at one year CK was predictable within ±0.50D in 62% of the patients studied and 89% of the patients were within ±1.00D. For the emmetrope not interested in LASIK, conductive keratoplasty may be appropriate.

LASIK goes multifocal

As far back as 1993, topography showed that hyperopic LASIK creates a multifocal effect on the cornea. This led researchers to develop LASIK programs specifically designed to enhance and create a true multifocal effect. VISX is currently working with clinical investigators in and outside the United States to produce a workable program that can customize this procedure. Using the variable spot size capabilities of the VISX Star 3, Bruce Jackson, M.D., achieved 20/40 uncorrected distance VA in all 20 patients in a study at three months post-op, while achieving 20/40 uncorrected near VA in 80% of the patients. Although a small sample, this study indicates that LASIK may soon be a formidable option for bilateral multifocal treatments.


Refractec's CK technology steepens the cornea in an outpatient procedure.

An IOL alternative

For the patients who don't want to wait for multifocal LASIK, there's an intraocular alternative: the Array lens from Advanced Medical Optics. The key to success with this lens is an acute understanding of the limitations and the benefits that it can provide the patient. Presbyopic lens exchange (PRELEX) works best for patients who require low to moderate hyperopic correction (although I have heard of success with high hyperopic corrections), average pupil sizes, minimal corneal astigmatism, and no significant night demands.

PRELEX with the Array lens is best performed bilaterally and although the results are immediate, it may take upwards of four to six months for patients to fully achieve the results. As with any multifocal effect, night vision glare is always a concern; the effect does, however, diminish over time. The superior optical quality of the lens (50% distance, 12.50% intermediate and 37.5% near focal zone) makes the Array a great option for qualified patients. But its use is only successful with the diligent preoperative counseling of the primary eyecare optometrist; moreover, this procedure is no different than cataract surgery, so the follow-up care holds no significant mystery.

The Array IOL is the product of Advanced Medical Optics

Multifocals multiply

The Array will soon have competition from Alcon Laboratories' acrylic diffractive pseudoaccommodative IOL. Now under clinical investigation, the AcrySof ReSTOR uses only the center 3.6 mm of the anterior surface for the diffractive portion. The diffractive pattern of the lens is graduated through a proprietary process called apodization; this process creates a controlled reduction in the diffractive step height from the center of the radius to the periphery. The diffractive region provides near and distance vision periphery. Light energy is equally divided between the near and distance for small pupils; it gradually becomes distance dominant in low lighting/large pupil conditions.


The AcrySof ReSTOR

The ability to use the AcrySof in patients who have large pupils and the apparent minimal photic phenomena are definite advantages for this lens. In fact, a multicenter study, in which Stephen Brint, M.D., is one of the investigators, will compare 300 patients implanted with the AcrySof ReSTOR with 200 monofocal patients. With 80% of enrollment completed, one of the most important findings has been the lack of significant difference between the observations of the patients in the ReSTOR group compared with the monofocal group in regard to glare, flare, nighttime vision problems or halos. The lens received European marketing approval earlier this year and clinical trials are continuing in the United States.

CIBA Vision has taken the multifocal effect and combined it with the early success of their phakic intraocular lens the Vivarte. The Vivarte is a three-point anterior chamber angle-supported lens combined with a distance correction in the periphery and central portion of the lens and near in the paracentral. Now under clinical investigation in Europe, the lens is successful, with 85% of the patients reporting no night vision problems and the remaining 15% only slightly worse than pre-op levels. However, because of reports of pupil ovalization and slight endothelial loss, the Vivarte requires more testing to determine its role in the treatment of presbyopia. A permanent yet reversible treatment option is appealing to skeptics of refractive surgery and will likely be repeated with other phakic lenses.

A postoperative hyperopic LASIK topography: Note the central steepening and peripheral flattening.

Pursuing accommodation

What about being able to restore the the eye's accommodative abilities? Surgical reversal of presbyopia (SRP), with the use of scleral expansion bands or laser, has been slow to gain steam in the United States secondary to the limited success and increased side effects. Therefore, lens options will dominate the SRP; with the early data, we'll soon see turning presbyopic as just another milestone.

Leading the pack of the accommodating IOLs is C&C Vision's CrystaLens. This lens sits in the capsular bag with a flexible haptic at each end of the lens allowing for anterior movement and thus creating the accommodative effect. An ultrasound biomicroscope shows that the contraction of the ciliary muscle forces the vitreous mass forward on the lens and thus creates an accommodative effect. Early studies show that the best results are obtained when the patient is slightly nearsighted, however, this limits the capabilities of the distance vision. Investigators found that a surgeon bias affects the outcome -- the size of the capsulorrhexis is especially important. With reports of fatigue, halos, redness, tearing and small optic zone (4.5 mm), this lens may take time to gain acceptance.


CIBA says that no night vision problems have been reported with the Vivarte.

The other accommodating lens is the HumanOptics Akkommodative 1-CU. The design features a central optic zone surrounded by a ring of silicone. The 1-CU works by the contraction of the ciliary muscle releasing the zonules, thus allowing forward movement. In a head-to-head study of the 1CU and CrystaLens, investigators found 1.50D to 2.00D of accommodative capabilities with both.

Keep an eye on the horizon

The refractive surgical treatment of presbyopia is at the earliest stages. New and exciting procedures are showing promise. This can only mean that our patients will benefit, so stay informed and prepare your patients for the onslaught of exciting new advances.

Dr. Bloomenstein is the refractive clinical medical director for the Barnet Dulaney Perkins Eye Center in Phoenix. He can be reached at (602) 955-1000 or Marc@bdpec.com.

 


Optometric Management, Issue: June 2003