BB&T Contributing Editor
Intraocular lenses are emerging as a major presence in ophthalmology with several introduced over the past three years, with ophthalmologists now attempting to determine which are the best performers.
At this year’s annual symposium of the American Society of Cataract and Refractive Surgery (ASCRS; Reston, Virginia), Mark Packer, MD, of the ophthalmic surgery practice Fine, Hoffman and Packer (Eugene, Oregon), told analysts that “aspheric IOLs clearly outperform spherical lenses” and that as a clinical investigator of the Tecnis lens, he clearly feels it is the best available aspheric IOL. “I believe that spheric lenses will eventually go by the wayside,” he said.
Advanced Medical Optics (AMO; Santa Ana, California) is now marketing the Tecnis multi-focal lens outside the U.S. and hopes to gain FDA approval in late 2007. Meanwhile, Alcon (Fort Worth, Texas) plans to expand the ReSTOR product line with new products, with the likely launch of an “IQ” (aspheric) version of the lens that will make it more competitive with AMO’s Tecnis multifocal. A toric version, which will take longer to bring to market, is also in the works.
“Our goal is to surround the ophthalmologist with a variety of refractive technologies and provide a complete solution,” Russ Trenary, chief marketing officer for AMO, told analysts.
A newcomer to the domestic refractive surgical scene is Lenstec (St. Petersburg, Florida). Its Tetraflex IOL has been CE-marked since 2003 as a solution to patients seeking accommodation for their presbyopia, but the company has been relatively unknown within the U.S.
Designed by Robert Kellan, MD, director of the Kellan Eye Center (Boston), the Tetraflex IOL is a foldable lens made of a hydrophilic acrylic, and its design appears to offer some advantages over existing technology. It is not designed on a hinge principle like the Crystalens, but rather on a configuration that allows the lens to move along with the entire capsular bag. Its optic is designed to act as a “sail,” catching the “wave” of vitreous to provide maximum forward movement for near vision and return to the intended plane in the “flat” position for clear intermediate and distance vision.
Getting the clinical treatment
Lenstec is quickly generating positive notice in the U.S. as its clinical trial is gaining significant momentum. Based upon strong European safety data, the company received FDA approval to begin a 300-patient pivotal trial last September and, according to a company spokesman, some 60 lenses have been implanted to date. Although it is too early to evaluate the U.S. data, it looks promising.
According to David Brown, MD, of the Eye Center of Florida (Fort Myers, Florida), the Tetraflex lens has been a “consistent performer so far,” with his patients achieving both excellent near and far uncorrected visual acuity. About half of the total patients implanted thus far have occurred at Brown’s center.
Deepak Chitkara, MD, of the Viewpoint Centre (Manchester, UK), reported solid clinical results and said that Tetraflex provides “true accommodation.” Chitkara has had the longest history with the Tetraflex and has implanted a large series of lenses.
Paul Dougherty, MD, Dougherty Laser Vision (Los Angeles), described his comparative experience with 70 Crystalens implants and 10 Tetraflex cases. So far, Dougherty has observed potential benefits for the Tetraflex IOL in several areas, including refractive accuracy, stability in the capsular bag, surgical technique, lens material, and optic size.
The company said it hopes to finish enrollment of the trial within the next few months and, after an FDA-mandated one year follow-up, could file its PMA application in late 2007 or early 2008.
Privately-owned, venture capital-backed Visiogen (Irvine, California) began its pivotal trial for the Synchrony dual optic accommodating IOL in late 2005 and will be vying with Lenstec as the next company to attain FDA approval for an accommodating IOL.
The Synchrony has now been implanted in more than 200 patients worldwide, and early reports demonstrate that the lens will have a greater accommodative range than single-optic vaulting designs, such as the Crystalens and the TetraFlex.
Surveying accommodative lenses
A presentation by Steven Dell, MD, Dell Laser Consultants (Austin, Texas) provided an excellent update of the many accommodative lenses that are either FDA or CE-mark approved.
He mentioned three single optic IOls: the Akkommodative 1CU IOL from HumanOptics (Erlangen, Germany), CE-marked and sold in Europe for several years; the Crystalens, both-FDA approved and CE marked; and the Tetraflex, which is CE-marked.
Several promising accommodative lenses are traversing the rocky shoals of either product refinement or clinical and regulatory trials. These include two dual optic lenses, the aforementioned Synchrony lens from Visiogen and the Safarazi dual optic lens from Bausch & Lomb (B&L; Rochester, New York) which, according to Dell, has yet to reach the human implant stage. Additionally, B&L has begun U.S. clinical trials with a single-optic accommodating IOL, the OPAL, a lens which was jointly developed with HumanOptics.
Further down the road but quite intriguing are lenses from three private companies – Medennium (Irvine, California), NuLens (Herzliya Pituach, Israel) and PowerVision (Belmont, California).
The Medennium Smart IOL – in a concept stage thus far – is comprised of a hydrophobic acrylic that has thermodynamic properties, enabling it to change shape once introduced into the capsular bag. The company has been seeking funding for many months and thus far has been unsuccessful.
The NuLens real accommodative IOL is unique in that it is designed to change its true power during accommodation. In animal models, it has delivered more than 40 diopters of accommodation. The basis of the concept involves pressing a soft material such as silicone against a hard plastic surface that has a round hole in it, enabling the soft material to bulge through the hole. Since the silicone material is transparent and has a different refractive index, that bulging essentially acts as a lens.
The birds’ eye view
A similar accommodating mechanism has been demonstrated in waterfowl. In these birds, a rigid muscular iris acts as a hard surface through which the crystalline lens bulges during the act of accommodation. This design allows for large accommodative potential through minimal movement, as the increase in the lens’ anterior radius of curvature is responsible for the large ranges of accommodative amplitude in waterfowl and in the NuLens RA-IOL.
The company has been performing a series of animal trials and it is likely that at some point in the relatively near future it will begin human trials.
Venture capital-backed PowerVision is developing a proprietary, fluid-controlled accommodating IOL which uses natural accommodating forces in the eye to transport fluids in the lens. In the eye, the lens goes from thin (unaccommodated) to thick (accommodated) as fluids move from the periphery of the lens through internal fluid channels to a piston-like structure in the center of the lens, thus deforming the anterior surface of the optic. This results in a shape change of the lens, similar to what occurs to the natural lens during accommodation.
The company believes that this approach will enable an accommodative range of up to 10 diopters, equivalent to the vision of a 25-year-old. PowerVision anticipates beginning its human trials outside the U.S. in late 2006 or early 2007.
Another accommodating IOL is the FlexOptic lens, which is being developed by AMO. The lens was invented by the founder of Quest Vision Technologies, which AMO acquired in May 2005.
AMO’s lens uses a flexible material designed to mimic the eye’s natural crystalline lens. The company it is pushing to begin its human clinicals as quickly as possible.