Ophthalmologists annually perform approximately 3 million cataract procedures in the US. More than 50% of these eyes need spectacle correction after surgery for optimal distance acuity.1,2 Thanks largely to the growing number of individuals who have undergone successful LASIK surgery, patients now have higher expectations than ever for their visual acuity after cataract extraction and IOL implantation. The Light Adjustable Lens (LAL; Calhoun Vision, Inc., Pasadena, CA) has the potential to provide patients with clear distance acuity without spectacle correction.

ADJUSTABILITY
The LAL resembles a silicone lens in appearance and material but can be adjusted noninvasively by means of a digital light delivery system (collaboratively designed by Calhoun Vision, Inc., and Carl Zeiss Meditec AG, Jena, Germany) after the cataract wound has healed. This unique technology relies on photosensitive silicone molecules embedded within a silicone matrix. For a hypothetical LAL patient with a postoperative refractive error of +1.00 D, the surgeon would irradiate the center of the lens with low-intensity, ultraviolet light. The 2-minute exposure would induce polymerization and migration of silicone molecules into the center of the lens, thereby thickening that area and creating emmetropia. Conversely, if the physician wished to reduce the power of the lens, he could simply irradiate its outer periphery. Once a patient has achieved the desired refractive state, the surgeon permanently fixes the lens power by irradiating the entire lens, an action that polymerizes all the remaining photosensitive molecules.

CLINICAL TRIAL
In January 2003, Arturo Chayet, MD, of Tijuana, Mexico, initiated the first clinical trials of the LAL in sighted eyes. As seen in the video, he performs a standard phacoemulsification procedure through a clear corneal temporal incision to remove the patient's cataract. He then implants the folded LAL using his standard technique (Figure 1). Two weeks postoperatively, Dr. Chayet refracted the patient depicted in the video. He later positioned the patient in front of the light delivery system for 2 minutes to induce an intended 0.75-D hyperopic shift in lens power (Figure 2). The patient tolerated the procedure well and experienced no discomfort during or after the adjustment. On the following day, the patient's refraction had changed by 0.50 D, nearly achieving the target. Dr. Chayet reports that the procedure is “simple and easy.”

CONCLUSION
The possibility of performing wavefront corrections on the LAL is even more exciting. In the laboratory, investigators applied a tetrafoil aberration pattern to the lens and then confirmed its presence by wavefront analysis. They have also created a tetrafoil patter in a rabbit model. The LAL may offer significant advantages over LASIK for wavefront correction because wound healing will not alter initially good results.

Robert K. Maloney, MD, is Director of the Maloney Vision Institute in Los Angeles, California. He holds a financial interest in the LAL. Dr. Maloney may be reached at (310) 206-7692; drmaloney@maloneyvision.com.
1. Javitt JC, Steinert RF. Cataract extraction with multifocal intraocular lens implantation: a multinational clinical trial evaluating clinical, functional, and quality-of-life outcomes. Ophthalmology. 2000;107:2040-2048.
2. Lum F, Schein O, Schachat AP, et al. Initial two years of experience with the AAO National Eyecare Outcomes Network (NEON) cataract surgery database. Ophthalmology. 2000;107:691-697.