November 2007

 

CATARACT/ IOL

 

Current and future innovations for acrylic IOLs


by Christine Hamel EyeWorld Contributing Editor

 

Acrylic IOLs chart

 

Cataracts are the most common eye disorder in North America, affecting half of the population aged 55 to 64 and 85% of the population older than 75. With the aging of the baby boomers in America, the need for cataract surgery has increased, which has driven the interest in improving IOL technology.

Specialty lenses Multifocals

Specialty lenses are one of the recent improvements in acrylic IOL technology that have addressed patients’ quality-of-vision concerns. Presbyopia-correcting IOLs offer the ability to see well at more than one distance, without glasses or contacts. Two multifocal lenses that were approved by the U.S. Food and Drug Administration (FDA) in March 2005 are the AcrySof ReSTOR IOL (Alcon, Fort Worth, Texas) and the ReZoom Multifocal Lens (Advanced Medical Optics, AMO, Santa Ana, Calif.).

AcrySof ReSTOR is a multifocal that uses apodized diffractive technology to provide correction. Kevin M. Miller, M.D., Kolokotrones Professor of Clinical Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, says that the central 3.6 mm of ReStor’s optic is diffractive for focusing on near and distance simultaneously while the outer portion of the lens is refractive for focusing on far distances. He says, “The idea within the Alcon lens is that someone is not going to be reading when their pupils are dilated 5 or 6 mm. It’s more likely they’ll be driving or outdoors, and Alcon wanted patients to have good distance vision when they’re dilated. In dim lighting, the lens gives good distance vision for driving purposes but not very good reading vision. Under normal lighting conditions, the lens provides good focus for distance and near.” This design minimizes halos around lights at night but makes reading in dim light more difficult.

Dr. Miller says that the next generation lens for Alcon will be the AcrySof ReSTOR aspheric IOL. “This one will add an aspheric front surface, so that there is no longer a net positive spherical aberration.” The lens is available now, but the official launch of the product will be at the American Academy of Ophthalmology (AAO) meeting in November. ReZoom is Advanced Medical Optics’ second-generation multifocal. It is a three-piece IOL with a zonal refactive optic design that distributes light over five optical zones to provide near, intermediate, and distance vision. When the pupil is small, in bright light, the ReZoom functions as a distance dominant refractive lens with no loss of efficiency. When the pupil opens to about 3.0 mm the near focal point becomes active. The zonal refractive design therefore provides a benefit for reading in dim light. Dr. Miller notes that ReZoom’s current zonal refractive lens design can produce prominent halos or glare around lights, particularly at night. Therefore, the complementary strengths and weaknesses of ReSTOR and ReZoom have led some surgeons to pursue the “mix and match” strategy.1 Currently under FDA-monitored clinical investigation in the United States and approved for use in Europe, is the Tecnis Multifocal Lens (AMO), which incorporates a diffractive design. Dr. Miller says that for any diffractive design, “When light hits the edge of a diffractive ring, it splits the light into multiple orders. The zero and first orders are used to create distance and near foci.”

The Tecnis Multifocal lens has a unique wavefront-designed optic for reduced spherical aberration and restored balance. Dr. Miller says, “The Tecnis Multifocal lens is going to use the aspheric optic design of the Tecnis lens, which is already on the market. And it’s going to add multifocal capability, similar to the original 811E lens marketed in Europe by Pharmacia [Peapack, N.J.].”

Torics

The FDA approved the AcrySof Toric IOL (Alcon, Fort Worth, Texas) in September 2005. Says Dr. Miller, “So far, they have three powers: 1.5, 2.25, and 3.0 dipopters in the lens plane.”

Dr. Miller says, “Alcon will eventually marry the toric lens to the aspheric multifocal lens, so there will be a toric, aspheric multifocal. Right now if someone wants a multifocal lens, but they have too much astigmatism, they’re not eligible. But pretty soon those people will be eligible, because we’ll have a toric optic that also happens to be multifocal.” He adds that the company is still waiting to hear whether the FDA will require a clinical trial to approve the product. Richard J. Mackool, M.D., director of the Mackool Eye Institute, Astoria, New York, senior attending surgeon at New York Eye and Ear Infirmary, and clinical professor, New York University Medical Center, New York, sees additional changes for torics in the future. “Right now we can only correct two diopters of corneal astigmatism, but there’s really no limit to how much astigmatism you can design the IOL to correct. I think soon that we’ll see corrections of up to five or more diopters of corneal cylinder,” says Dr. Mackool.

IOL and biodevice researchers, designers, manufacturers and surgeons have expended much energy and money in an attempt to create and market these exciting “specialized” IOLs. David J. Apple, M.D., professor of ophthalmology and pathology, Unveristy of Utah, Salt Lake City, noted that “as we continue to study the overall development of lenses one should not overlook basic lens safety and efficiency. Research and development need to ensure that present cataract-IOL surgical techniqes and lenses are capable of serving as platforms for future models.”

Dr. Apple and his colleagues, Guy Kleinman and Mr. Brian Zaugg are presently evaluating various “specialized” IOL designs and materials in relation to posterior capsular opacification (PCO). He and his colleagues have also gone on to recommend that surgical techniques and IOLs which require long term clarity and stability mandate careful review and selection. An example of a recent modification includes the addition of a 360-degrees edge configuration which has been added to a recently launched AMO design. “This is an important component; I believe it will turn out to be one more useful factor in impeding the growth of cells over the visual axis,” noted Dr. Apple.

Photochromics

Some lenses, such as AcrySof Natural IOL (Alcon, Fort Worth, Texas), which was approved by the FDA in September 2005, filter both UV and high-energy blue light. Now the Photochromic Aurium hydrophobic acrylic lens (Medennium, Irvine, Calif.) is on the market in Europe.

“The lens is colorless, but the optic becomes yellow when exposed to UV light, so there are no concerns about any possible effect of the yellow optic on night vision,” says Liliana Werner, M.D., Ph.D., research associate professor, John A. Moran Eye Center, University of Utah, Salt Lake City, and director of preclinical research, Berlin Eye Research Institute, Germany Dr. Werner and her coworkers performed studies in vitro and in vivo in a rabbit model to test the effectiveness of Aurium. Those and clinical trials in Mexico showed positive results. The lens is thought to allow patients better night vision while aiding in the protection of retinal damage from blue and UV light and age-related macular degeneration. In March 2007 CE Mark clearance was received for marketing Aurium in Europe, making it the first and only photochromic IOL introduced in the cataract lens industry.

Dr. Apple noted that the “aforementioned photochromic IOL is fabricated from a hydrophobic acrylic material, and thus impacts PCO as noted earlier. Furthermore, I have never been fully convinced as to the value of retinal protection by various blockers...”

Considerations

Dr. Mackool says that a majority of the patients will eventually receive a specialty lens. “Most of the IOLs that I’m using today weren’t even available four or five years ago. So that’s a pretty big quantum leap,” says Dr. Mackool.

However, he notes that it raises the question of which surgeons will be able to implant these lenses. “More and more of these new lenses that offer refractive advantages will be outside the realm of government reimbursement,” says Dr. Mackool. “Some patients will not be happy if a technology that they might be interested in isn’t offered to them. So it is in everybody’s interest, the surgeon and the patient, to have an honest discussion preoperatively about the pros and cons of [specialty] IOLs, so that the patient can choose his/her best option.”

Editor’s note: Dr. Miller has financial interests with Alcon (Fort Worth, Texas) and Hoya Optics (San Jose, Calif.). Dr. Mackool has a financial interest with Alcon. Dr. Werner’s studies were partially supported by a research grant from Medennium (Irvine, Calif.).

Contact Information

Apple: djapple@comcast.net 

Mackool: 718-728-3400, MackoolEye@aol.com 

Miller: 310-206-9951, kmiller@ucla.edu

Werner: liliana.werner@hsc.utah.edu, werner.liliana@gmail.com

1 Pepose JS, Qazi MA, Davies J, et al. Am J Ophthalmol 2007; 144(3): 347-357.

Current and future innovations for acrylic IOLs Current and future innovations for acrylic IOLs
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