EyeNet Magazine


 
Clinical Update: Cataract
Steady Progress on the Light-Adjustable Lens
By Jean Shaw, Contributing Writer
 
 

Of all the innovative IOLs currently in the research pipeline, the light-adjustable lens is perhaps the most eagerly anticipated. After all, its developers say, this is an IOL that can be adjusted postoperatively to correct for higher-order aberrations and common postsurgical refractive errors—a boon in this age of demanding patients with high expectations.

It will be some time before the light-adjustable IOL (LAL; Calhoun Vision) is available on the U.S. market. But with clinical data emerging from work abroad, and research sites being selected in this country, cataract surgeons are beginning to get a sense of the LAL’s potential. “The rising tide of patient expectations—along with the variability in results with current IOL technology—has really opened the door” for an IOL such as the LAL, said Francis W. Price Jr., MD, medical director of the Price Vision Group in Indianapolis. He added, “A number of companies are working on toric or aspheric lenses to minimize residual refractive errors. But this IOL has the potential to provide customized correction for each individual eye. This is like the difference between buying a suit off the rack and having one custom tailored.”

How It Works

The idea for the LAL “came from research on ways to get a scleral buckle that would adjust itself,” said Randall J. Olson, MD, chairman of ophthalmology at the University of Utah. “With silicone IOLs, there are still spaces on a molecular level within the IOL. In the LAL, these spaces are filled with light-sensitive, free-floating macromolecules,” said Dr. Olson, who is the medical monitor for the upcoming U.S. clinical trials of the lens. “If the right wavelength of light hits one of the macromolecules, it will attach to the silicone, and what’s left will redistribute itself and reshape the IOL.”

Specifically, the free-moving photosensitive macromolecules are fixed in place through polymerization when the surgeon shines UV light in the near range (365 nm) on the lens. When some of the macromolecules are polymerized, the remaining macromolecules redistribute through the lens, changing its shape and refractive power.

The UV light is delivered with a digital light delivery device, made by Carl Zeiss Meditec. This allows “a precise pattern on the lens that can be controlled,” Dr. Olson said. As a result, the LAL can be customized to treat spherical, cylindrical and other higher-order aberrations as well as to create refractive multifocality and diffractive bifocality. “Spherical aberration has been one of the weaknesses with traditional IOLs,” Dr. Olson noted. “If the IOL is decentered a little from the optical axis, then the effect drops dramatically. But with the LAL, you can actually correct on the axis.”

One of the LAL’s appealing qualities is that you can “redo the correction until you get it right,” Dr. Olson said. “You can adjust it to see how the patient likes it.” Once it is finally adjusted to the patient’s satisfaction, the surgeon “applies light over the entire LAL to lock in the molecules of the lens so they won’t react further to ambient UV light,” Dr. Olson said. “At that point, the LAL becomes a regular silicone lens.”

Beyond Proof of Concept

Initial clinical results with the LAL have been promising. In as-yet unpublished animal research, researchers at the University of Utah have confirmed the accuracy of the correction for higher-order aberrations, Dr. Olson said.

In people, Arturo S. Chayet, MD, who has performed the bulk of the clinical investigations to date, has implanted the LAL in more than 50 eyes. Corrections ranged from 0.5 D to 1.75 D, said Dr. Chayet, medical director of the Institute de Oftalmologia in Tijuana, Mexico. Overall, he reported that “95 percent of eyes are within 0.25 D of the intended results.” Dr. Olson commented, “It’s hard to measure more accurately than that.”

Thus far, the length of follow-up is approximately one year, Dr. Chayet said, and the results of the corrections are stable. “Patients are basically back to BCVA—20/20—and they are very happy; their vision is nice and sharp.”

Looking Forward

Some issues to consider as the research continues:

Approval timeline. Early this year, the LAL was approved for use in Europe with the full CE Mark. But those familiar with the lens caution that U.S. approval will take some time. “I think we’re looking at phase 2 studies in this country during the first quarter of 2008,” Dr. Olson said. It’s possible that approval might come in 2009 or 2010, he said, but he cautioned that that’s an optimistic assessment. “We will want to carefully evaluate the outcomes with each and every patient,” he said, adding, “Canada will probably have the LAL much sooner than that, which raises the possibility that patients will be going over the border for the lens.”

Patient selection. The LAL can “basically be used in anyone with astigmatism, up to 1.5 D,” Dr. Chayet said. “It does seem best if the cornea is relatively clear, with minimal opacities.”

Dr. Price noted that patients who’ve had previous laser refractive surgery may especially benefit from the LAL.“With current IOLs, these patients are our biggest challenge—the predictive for-mulas are not very accurate. While most patients do well, a number have unex-pected results.”

Expanded applications. Dr. Olson expects that the LAL could be used as a piggyback lens. “It would fit on like a contact lens that you could tweak and adjust.” He also noted that it could be used as a phakic IOL or in a dual-optic.

Money issues. While the question of reimbursement is still under discussion, odds are that the LAL won’t be covered by Medicare, at least initially. “But for most patients, once they get the lens, they’ll have it the rest of their lives,” said Dr. Price. “Many may feel it is well worth it to pay a little extra to get really crisp vision.”

Interest is running high among cataract surgeons, Dr. Price said, “especially among those who are working with the presbyopia lenses, where any residual refractive error can really degrade quality of vision.”

He added, “You know, 10 years ago, if patients still had to wear glasses [after cataract surgery], they didn’t make too much of a fuss. Now, that’s not true. And with some of the newer IOLs, you don’t want to have any refractive error left, as you end up having to make incisions in the cornea or do another touch-up procedure. It would be so much cleaner and more precise if we could use a laser to accurately treat from the start. That would be much more stable than operating on the cornea.”

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Dr. Chayet reports no proprietary interest in the LAL. Dr. Olson is head of Calhoun Vision’s medical advisory board and owns stock in the company. Dr. Price is a member of the medical advisory board and owns stock in the company.

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Current Controversies will be the focus of Spotlight on Cataract Surgery at the Annual Meeting in New Orleans. Rapid-fire talks by leaders in the field will tackle issues in phaco, IOLs and cataract pharmacology.

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