April 2019


Innovations in Lenses
An eye on future vision
Adjustable lens technology continues to improve

by Vanessa Caceres EyeWorld Contributing Writer

A rabbit eye implanted with a monofocal commercially available hydrophobic acrylic lens, which underwent refractive power adjustment by femtosecond laser
Source: Liliana Werner, MD, PhD

The Zepto capsulotomy achieved perfect 360-degree
overlap of the Light Adjustable Lens so with capsule fibrosis, the lens is stable and does not tilt or decenter.
Source: John Berdahl, MD

Adjusting the power of the Light Adjustable Lens
Source: John Berdahl, MD

Dr. MacRae performs the first-in-human study of corneal LIRIC. Pseudophakic patients with monofocal IOLs were treated with a diffractive multifocal refractive index wavefront in the corneal stroma.
Source: Clerio Vision

Eye surgeons in the U.S. are still anxiously awaiting the possibilities of adjustable IOLs as the technology itself continues to become more sophisticated in lab and clinical studies.
At one point, there was one IOL in this category—the Light Adjustable Lens (LAL, RxSight). Now, the offerings have expanded to include the Perfect Lens (Perfect Lens LLC) procedure and technology from Clerio Vision that allows for an adjustment of the cornea, contact lens, or IOL.
“All of our latest advances in preoperative biometry, intraoperative aberrometry, and IOL formulae have helped us to reduce the mean error and standard deviation of our IOL calculations,” said David F. Chang, MD. “However, these methods are still generating a prediction of the best IOL power to select and still rely on assumptions of the effective IOL position, surgically induced astigmatism, and posterior corneal astigmatism. We assume posterior corneal curvature based on the anterior corneal curvature, and this can introduce additional errors with keratoconus and post-LASIK eyes.” This becomes even more complex with toric IOL calculations, Dr. Chang added.
“With an adjustable IOL, we would wait until the IOL can no longer rotate or shift axially before treating the net postoperative refraction. We would no longer have to rely on preoperative assumptions,” he said. The precision and accuracy of an adjustable lens will be especially valuable for difficult eyes, such as those post-LASIK, post-RK, extremely long or short eyes, oblique astigmatism, or eyes with mature cataracts that precluded preop optical biometry, he explained.
Here’s a summary of recent advances in adjustable lens technology and when surgeons in the U.S. may find it clinically available.

Light Adjustable Lens

The LAL, which the U.S. FDA approved in late 2017, uses a proprietary ultraviolet light treatment that produces modifications in the lens curvature. The technology allows surgeons to reshape the lens based on a patient’s individual vision correction needs after cataract surgery. The lens is approved in the U.S. to correct hyperopia, myopia, and astigmatism. Use of this approach requires both the LAL and a Light Delivery Device.
“Many surgeons are eagerly awaiting the launch [of the Light Adjustable Lens],” said John Berdahl, MD. “There are post-approval studies that are underway. I am hopeful that the technology is available in the next 12 to 18 months commercially.” Dr. Chang was a clinical investigator for the U.S. clinical trial and predicts that the technology will become available in the U.S. later this year.
Although Nick Mamalis, MD, is now working with the Perfect Lens, he and colleague Liliana Werner, MD, PhD, performed the animal and lab studies for the LAL. “It’s a very interesting technology that can change the power of the lens implant,” Dr. Mamalis said. However, it does require the use of a special IOL made by the company versus the use of a non-specific IOL, he said.

Perfect Lens

Dr. Mamalis and Dr. Werner now work with the Perfect Lens procedure, which uses a femtosecond laser to modify an implanted IOL. Surgeons can use the technology to correct spherical aberration, asphericity, toricity, and multifocality.
Perfect Lens has created a femtosecond laser system for IOL power adjustment based on refractive index shaping.
“Refractive index shaping combines a device, a mechanism, and a process,” Dr. Chang said. “The device employs a femtosecond laser, an OCT, a scanner, and a proprietary objective lens. The mechanism is a laser material interaction that changes the refractive index of the targeted material. The processing is an algorithm that uses this mechanism to create a diffractive or refractive lens by modulating the laser energy and controlling the position of the refractive index change inside the IOL. Refractive index shaping is theoretically available for any hydrophilic or hydrophobic intraocular lens.”
The Perfect Lens technology also can be used several times and can reverse adjustments made previously, Dr. Werner said. The approach can create multifocality in a monofocal lens and turn that same IOL back into a monofocal if necessary. “It can also cancel the diffractive multifocal add of a traditional IOL, all without significant changes to the IOL optic quality,” Dr. Werner said.
Drs. Werner and Mamalis have published studies related to the Perfect Lens technology. “What I find impressive is that it’s extremely precise,” Dr. Mamalis said. “In the lab, when we’re changing the power of a lens, it’s accurate to one-tenth of a diopter of a correction.” In rabbit studies, there have been no signs of inflammation after corrections or any problems with toxicity when examining the histopathology, he said.
Current studies of the Perfect Lens technology have been done in the lab, but clinical studies should start relatively soon, Dr. Mamalis said.


Clerio Vision introduced an approach called laser induced refractive index change (LIRIC). “Laser induced refractive index change works by focusing a femtosecond laser beam into the IOL material,” said Len Zheleznyak, PhD. “Within the laser focus, the native refractive index of the IOL material is adjusted by a predetermined amount. With this technology, it is possible to correct refractive error, such as sphere and cylinder.” It is also possible to induce and remove multifocality and correct the eye’s higher order aberrations.
The LIRIC approach is under development for compatibility with a range of widely used IOLs. It also can be used with the cornea and contact lenses.
Scott MacRae, MD, presented information at the 2019 Hawaiian Eye Meeting about the first-in-human study of corneal LIRIC. A total of 27 eyes have had the LIRIC approach for presbyopia correction. No degradation of far vision occurred, and there was a significant improvement in intermediate and a moderate improvement for near vision after LIRIC, Dr. MacRae said.
“We demonstrated the writing of diffractive optics into the corneal stroma of subjects implanted with monofocal IOLs,” Dr. Zheleznyak said. “We expect this procedure to be followed by a version of LIRIC where the LIRIC patterns can be written directly into the IOL instead of into the cornea.”
Studies with LIRIC are still underway. Dr. Zheleznyak anticipates that it will be available commercially in late 2022 or early 2023.

At a glance

• A growing number of companies offer IOLs that can be adjusted after cataract surgery.
• The LAL has been around the longest and is approved by the U.S. FDA. However, it is not yet available commercially in the U.S.
• Perfect Lens offers technology that allows for adjustment of a lens with a low-energy femtosecond laser.
• The LIRIC approach also uses a femtosecond laser to adjust an IOL, cornea, or contact lens.

About the doctors
John Berdahl, MD
Vance Thompson Vision
Sioux Falls, South Dakota

David F. Chang, MD
Clinical professor,
University of California,
San Francisco

Scott MacRae, MD
Flaum Eye Institute
University of Rochester
Rochester, New York

Nick Mamalis, MD
Professor and co-director
Intermountain Ocular Research Center, John A. Moran Eye Center
University of Utah
Salt Lake City

Liliana Werner, MD, PhD
Professor and co-director, Intermountain Ocular Research Center, John A. Moran Eye Center
University of Utah
Salt Lake City

Len Zheleznyak, PhD
Vice president of vision science Clerio Vision
West Henrietta, New York

Financial interests
Berdahl: RxSight
Chang: Perfect Lens, RxSight
Mamalis: Perfect Lens
MacRae: Clerio Vision
Werner: Perfect Lens
Zheleznyak: Clerio Vision

Contact information
: johnberdahl@gmail.com
Chang: dceye@earthlink.net
MacRae: scott_macrae@urmc.rochester.edu
Mamalis: nick.mamalis@hsc.utah.edu
Werner: Liliana.werner@hsc.utah.edu
Zheleznyak: lzheleznyak@cleriovision.com

An eye on future vision Adjustable lens technology continues to improve An eye on future vision Adjustable lens technology continues to improve
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