Artificial lens may help cataracts

February 5, 2010

Eye-opener — Engineer Paul Hamilton (standing) and ophthalmologist Nathan Ravi, chief of staff at the St. Louis VA, collaborated to build a robotic "lens stretcher" that mimics the function of the ciliary muscle inside the human eye. The machine helps Ravi's team learn how a natural lens focuses and has guided their design of a synthetic replacement lens made from a nanocomposite hydrogel. (Photo by Jerry Naunheim)

An auto-focusing artificial lens that turns from liquid to gel after being implanted in the eye may one day be a leap forward in cataract care, says the inventor of the technology.

Nathan Ravi, MD, PhD, and his team at the St. Louis VA and Washington University are developing a lens based on nanomaterials that mimics the soft, pliable lens of the human eye. In cataracts, the normally transparent lens becomes cloudy. Even advanced cases can usually be fixed through surgery, in which a prosthetic lens is placed inside the eye. But current prosthetic lenses have only limited focusing power, and most patients still need to wear glasses.

According to Ravi, his lab's artificial lens could potentially restore natural focusing ability. Plus, it could be placed in the eye through a technique that is less invasive than current cataract surgery.

Besides fixing cataracts, the lens could potentially be used to correct near- or farsightedness. That would be an elective procedure, says Ravi, similar to laser eye surgery, whereas cataract procedures are medically necessary to preserve vision.

To help develop their artificial lens, Ravi's group invented a robotic device that mimics the action of the ciliary body, the muscle in the eye that stretches the lens and thus enables it to focus. The octopus-like machine, with eight stainless-steel arms, simulates the natural movement of the eye as it shifts focus. In real life, says Ravi, this movement "occurs almost instantaneously and imperceptibly."

By measuring the dynamic forces involved in focusing, the researchers have been able to design an artificial lens that responds to the ciliary muscle as would a natural lens.

"This [device] is unique to our lab and has enabled us to characterize the timedependent mechanical response of the lens," says Ravi.

The group has also developed a related product to replace the vitreous gel, the clear "jelly" that fills the space behind the lens. In a procedure called a vitrectomy, doctors remove this part of the eye to treat a number of vision-threatening conditions. Ravi said the hydrogel his group is now testing in rabbits may be more biocompatible than the vitreous replacements currently in use. He said the nano-gel could also potentially be used to hold the retina in place in cases of traumatic eye injury.

This article originally appeared in the February 2010 issue of VA Research Currents.