Nearly three million cataract surgeries are performed every year in the United States. The majority of patients must wear prescription glasses after the procedure to see properly. But a new technology may eliminate this problem.
Based on technology developed by researchers from UCSF and Cal Tech, Calhoun Vision, Inc. is developing a photosensitive silicone intraocular lens. This lens can be adjusted - non-invasively, weeks after surgery—with a low-power source of light to eliminate refractive errors post implantation.
Preliminary findings regarding this technology are being presented at the American Society of Cataract and Refractive Surgery in Philadelphia June 1-5, 2002.
Currently, patients experience refractive errors after cataract surgery because of unpredictable wound healing, inaccuracies in pre-operative measurements of ocular dimensions, or pre-existing corneal disorders such as astigmatism. “With this technology, we can make power adjustments after the lens is in place, wound healing has occurred, and the eye is stabilized,” said Daniel Schwartz, MD, UCSF associate professor of ophthalmology, director of the UCSF retina division and a co-inventor of the Light Adjustable Lens (LAL™).
“As currently envisioned, the procedure will be relatively simple. The surgeon would implant the LAL™ using standard surgical techniques. When the eye has healed after two to four weeks, the patient returns to have the lens customized. By directing a cool, low intensity beam of light onto the lens, the surgeon would precisely adjust the lens power to the patient’s specific needs. The lens material is photosensitive and designed to respond in a predictable manner according to the duration and intensity of light delivered,” said Schwartz.
Initial human trials are expected to begin in the summer of 2002. U.S. clinical trials will follow only with FDA approval. It is anticipated that the lens will be available commercially in Europe in late 2003 and in the United States by 2006.
The in vivo fine-tuning is based on the interaction of light and photosensitive materials (macromers) that reside throughout the lens. If the implanted lens is under-powered, the physician directs the beam of light to the center of the lens. This causes the macromers in the irradiated area to bind together to form a polymer. The unreacted macromers in the non-irradiated area then move toward the center to equalize their concentration throughout the lens. This physical movement of material causes a swelling in the irradiated area - and an increase in lens power. The physician locks in the optimized LAL™ power by treating the entire lens with light, thereby consuming all remaining macromers.
For the opposite effect—a reduction in lens power - the physician would treat the periphery of the lens instead, driving unreacted macromers to that area. The treatment of astigmatism, a commonly occurring irregularity of the cornea that causes blurred vision, could be accomplished in a similar fashion, by suitably orienting the light beam.
In another presentation, Nick Mamalis, MD, professor of ophthalmology at the University of Utah, will summarize research from animal testing of Calhoun Vision, Inc.‘s light adjustable lenses. Research on rabbits has shown an absence of inflammation or other adverse effects, predictable power changes after irradiation, and high optical quality, according to Mamalis and Calhoun Vision, Inc. scientists.
The researchers note that this technology may have application beyond correcting vision problems in post cataract surgery patients. The lens could potentially be used as an alternative to LASIK surgery for severe myopia (nearsightedness), said Schwartz. He explained that LASIK surgery for severe myopia has resulted in complications including glare, halos and unpredictable refractive outcomes. LALs™ may also be effective in treating farsightedness, which often cannot be treated optimally with LASIK surgery. The ability to implant and precisely adjust lens power post-operatively offers farsighted patients a wider range of correction and potentially more predictable outcomes than LASIK.
Funding for the initial research was provided by That Man May See, Inc. Additional researchers working with Calhoun Vision, Inc. include Robert Grubbs, PhD, professor of chemistry at Cal Tech; Julia Kornfield, PhD, professor of chemical engineering at Cal Tech, and Jeffrey Hubbell, PhD, formerly of Cal Tech and now professor of biochemistry at the University of Zurich.
Calhoun Vision, Inc. is a privately held company engaged in developing and commercializing novel technology combining advanced principles in chemistry and optics. The company, founded in 1997, is headquartered at 2555 East Colorado Blvd., Pasadena, CA. For more information, visit www.calhounvision.com.
Schwartz has a proprietary interest in this technology, as do all Cal Tech researchers. Mamalis has no proprietary interest.