The eyes have it: Analysis improves artificial lens design
During cataract surgery, an ophthalmologist generally replaces a cloudy lens with an artificial one that — in theory — should help a patient see more clearly.
Made of plastic, acrylic or silicone and available in either flexible or rigid varieties, current artificial lenses aren’t designed to mimic natural lens function.Consequently, patients gain unobstructed vision but require glasses to help them focus on objects up close.
The problem has bothered medical doctor Gerald Clarke for some time. Based in Appleton, Wisconsin, Clarke and colleagues own OptiVision Laser Centers and offer eye-care services, including LASIK vision-correction and cataract surgeries, in three Wisconsin cities.
About five years ago, Clarke developed a biomimetic artificial lens design, which takes into account the way eye muscles control lens curvature to adjust focus. He submitted a patent application for the design and asked Engineering Physics Professor James Blanchard and Researcher Carl Martin to evaluate it before he prototypes it.
The two are conducting a finite-element analysis, but the process is anything but straightforward. Optics researchers lack a clear understanding of eye muscle forces, so Blanchard and Martin are applying assumed forces in their calculations. In addition, Clarke’s design incorporates a silicone oil “pocket” in the center of a solid lens, and few researchers have experience in finite-element models of materials that combine liquids and solids. Blanchard and Martin, however, recently applied similar techniques in a study of safe nuclear reactor design.
Although their analysis of Clarke’s lens is still under way, Blanchard’s and Martin’s initial calculations showed there’s room for improvement. “We’ve already made some design decisions based on what they’ve showed us,” says Clarke.