June 2011

 

COVER FEATURE

 

Next-generation accommodating IOLs: A status update


by Faith A. Hayden EyeWorld Staff Writer

   

Tetraflex, Synchrony to be approved soon

The Tetraflex

The Tetraflex Source: Paul J. Dougherty, M.D.

Tetraflex accommodative IOL A case with the Tetraflex accommodative IOL demonstrating an enhanced refractive range into myopia with near focus Source: Paul J. Dougherty, M.D.

This year may finally be the year the Crystalens (Bausch & Lomb, Rochester, N.Y.), a silicone, hinge design, accommodating IOL, has some competition. The long-awaited Tetraflex (Lenstec, St. Petersburg, Fla.) should garner the coveted FDA stamp of approval soon, becoming a serious market rival.

"The company thought it might get FDA approval before the ASCRS Annual Meeting [in March], but it still hasn't heard," said Paul J. Dougherty, M.D., clinical instructor of ophthalmology at the Jules Stein Eye Institute, UCLA, medical director of Dougherty Laser Vision, Los Angeles, and clinical investigator of the lens. "I look forward to having access to this technology for my patients because my clinical trial patients were so happy with their results." The Tetraflex has a 2.2-millimeter injector allowing surgeons to make a 2.5-mm or 3.0-mm incision. The lens itself is made of hydrophilic acrylic with closed loop haptics and a 5-degree anterior angulation. "This is like any other IOL implantation," said Dr. Dougherty. "It's an extremely easy lens to put in. When it comes out, it will be the most accurate premium lens in the U.S. in terms of refractive outcomes. It is manufactured to a tenth of a diopter tolerance, which is better than any other premium IOL in the world. It's going to come out in quarter diopter steps between 15 and 25."

Dr. Dougherty acknowledged that it is critical that the lens haptics be positioned properly at the time of implantation. He suggested using a lens hook to move the Tetraflex nasally and temporally to make sure the haptics fully unfold in the capsular bag. In terms of quality of vision, in the clinical trial Dr. Dougherty found that 75% of patients were completely reading glasses independent or only minimally dependent in low lights or for fine print. His patients are currently achieving about 0.5-1.0 D of accommodation with the Crystalens, but it is estimated that patients will achieve approximately 1.5 D of accommodation with the Tetraflex. "The main upside of this accommodating lens is the quality of vision; it's spectacular," he said. "There are less glare, halos, and contrast sensitivity issues than with multifocals. The downside is the percentages of patients reading at the 20/20 or 20/25 levels are not as high. The multifocals give crisper near vision, but there are visual side effects. With the Tetraflex, patients get good functional near vision and superb distance vision without those side effects." Dr. Dougherty has been unhappy with the Crystalens and has actually "abandoned" it because of Z syndrome occurrences, unsatisfactory accommodation, and issues with refractive errors. "With hinges, you don't know where the lens is going to end up with respect to the nodal point," he explained. "The Tetraflex doesn't have hinges." John A. Hovanesian, M.D., Jules Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, however, uses the Crystalens for the majority of his presbyopia-correcting IOLs. "I feel very safe in using it," he said. "It's a safe lens to use, and it most closely mimics the way the eye was designed to work."

Dr. Dougherty couldn't reveal a price of the Tetraflex yet, but did indicate it should be treated as a premium IOL and priced as such. Other lenses that are in the pipeline include the Synchrony (Abbott Medical Optics, AMO, Santa, Ana, Calif.), NuLens (NuLens Ltd., Israel), the AkkoLens (AkkoLens International, the Netherlands), and the Electro-active AutoFocal Intraocular Lens (Elenza, Roanoke, Va.). All have varying diopters of accommodation, with the NuLens expecting to have a 4 D to 8 D range and the Synchrony from 1.0 D to 1.5 D, depending on patient age, said Jorge Ali, M.D., Instituto Oftalmologico de Alicante, Spain, and clinical investigator for the Synchrony, NuLens, and AkkoLens.

"There is a range of variability and each lens behaves differently," he said. "The variability reflects the complex condition of accommodation whose mechanism is partially by these lenses. Variability is related to ciliary body action, age, anatomic issues related to the capsule, and capsular bag fibrosis." Whereas the Synchrony, Crystalens, and Tetraflex are intracapsular accommodating lenses, the NuLens and AkkoLens are sulcus placed lenses. The AkkoLens has been used in a handful of European patients with "very promising" but confidential outcomes thus far, said Dr. Ali. "The AkkoLens is implanted in the sulcus and takes advantage of the forces generated in the capsular zonular fiber system to induce changes in the displacement of two sinusoidal surfaces, which are created following the Alvarez principle," he said. "The clinical application of the lens is already a fact as they are being implanted in Alicante."

For truly unique technology, look no further than the Elenza lens, the first electrically activated IOL. The lens is purely experimental so far and will stay that way for some time, but still provides a fascinating glimpse into the future. "The activation of the lens leads to a change in its power based on changes induced in the physical characteristics of the optics," said Dr. Ali. "Elenza may create a completely new concept in intraocular devices. It's not only about the lens, but the technology being used; it is so sophisticated that it might lead to a cascade of intraocular devices, which would be perfect to measure variations in intraocular disease, IOP on a real basis, and many other issues." Accommodative IOL article summary

All three of these lenses are years away from reaching U.S. soil, but Synchrony, which AMO obtained when it acquired Visiogen in 2009, is currently in front of the FDA and could gain approval this year or next. Synchrony is a dual-optic accommodating IOL that uses a preloaded disposable injector allowing for controlled implantation into the bag. Currently, the incision needs to be around 3.8 mm, which does increase the chance of surgically induced astigmatism (SIA). Studies have shown that SIA stabilizes within .5 D by 3 months post-op.

Furthermore, making a circular and centered capsulorhexis of less than 5 mm is crucial; if it's too big the lens won't be retained in the bag.

"There is no question the Synchrony accommodates to a very acceptable degree," said Dr. Hovanesian. "The challenge it will face is that not every surgeon is ready to implant a lens this mechanically complex. The company has done a brilliant job of creating an injector system that, at the time of approval, will probably go into an incision less than 3 mm in size, but you have to have some faith that the lens will unfold the way it's designed to. Not all surgeons are ready for that. It will be well suited for femtosecond laser surgery."

Dr. Dougherty agreed. "From what I understand, it's a much more difficult surgery. For the average surgeon, it's going to be a much more challenging lens." All of this, of course, is speculation. The technology is sure to develop and evolve between now and when most of these lenses are approved. "Right now we can only talk about these lenses conceptually and what we expect to see," said Dr. Hovanesian. "The new lenses are more complicated in their design and implantation, but will probably deliver accommodation that is much closer to what nature did in a young, healthy eye."

Editors' note: Dr. Dougherty has a financial interest with Lenstec. Dr. Hovanesian has financial interests with AMO and Bausch & Lomb. Dr. Ali has financial interests with AMO, AkkoLens International, and NuLens Ltd.

Contact information

Ali: jlalio@vissum.com
Dougherty: flapzap@gmail.com
Hovanesian: drhovanesian@harvardeye.com

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