Jan 22, 2003 ( http://www.latc.com/2003/01/22/special_sect/your_health.story04.print.html )

Nanotech may aid vision for people with eye diseases

By Cynthia Marshall Schuman

Special to the Town Crier

There's hope for some 15 million Americans who have age-related macular degeneration (ARMD) and retinitis pigmentosa (RP). Scientists from NASA Ames Research Center and Stanford University Medical Center are working jointly on Vision Chip, a project whose goal is restoring vision to people blinded by these diseases.

Using advances in both biotechnology and nanotechnology, researchers believe they can implant a device into the retina to give sight to people with ARMD, which is the leading cause of blindness in people over 55.

Age-related macular degeneration is caused by the death of photoreceptor cells, which are specialized cells in the eye that detect light.

The photoreceptors die following the demise of a supportive layer of cells called the retinal pigment epithelium (RPE).

"Photoreceptors are responsible for converting optical energy into electrical energy," said David Loftus, M.D., Ph.D., and the principal scientist on the project.

Once converted, the electrical impulses travel via established neural pathways to the optic nerve, then to the brain, where they are interpreted.

Although the photoreceptors die, the nervous system's pathways to the optic nerve and the brain remain healthy and usable. All that's needed to restore vision is a way to detect light and hence, images.

Charge-coupled devices (CCDs), which are used in things like home-video recorders, can convert images to electrical impulses. Loftus explained that to work, a CCD could be simply attached to a pair of glasses.

The real challenge of the NASA/Stanford Vision Chip project then is not so much inventing a light detector, but rather developing an interface between the detector and the patient's retinal tissue. This is where nanotechnology comes in.

Briefly, nanotechnology is the study of things on the scale of 10-9 meters and below very, very small things. The particular technology used by the Vision Chip project is called a carbon nanotube (CNT). The diameter of a CNT is roughly one-fiftieth that of a strand of hair and CNTs conduct electricity.

"The interface between the CCD and the retina will consist of a silicon chip, which forms the substrate or the base for an array of carbon nanotube towers," Loftus said.

The chip would be implanted into the retina in order to deliver signals to the eye's nerve-cell layer. Signals could be delivered between the CCD and the nerve cells using localized FM frequency radio transmitters, Loftus said.

Loftus maintains that CNTs are ideal for this setup, given their electrical conductivity, their strength, their ability to penetrate retinal tissue without damaging it, and their biocompatibility.

The Vision Chip isn't the only possibility for ameliorating ARMD. Working with the knowledge that ARMD is caused by the death, first of RPE cells, then of the photoreceptor cells, the NASA and Stanford scientists reasoned that another way to restore vision would be to replace the lost RPE cells before their absence could be felt by the photoreceptors.

This solution would call for harvesting some of the patient's own RPE cells, growing them on something called Bucky Paper, then returning the new cells back to the patient (called autologous transplantation).

Bucky Paper is a meshwork of CNTs that lie flat like a piece of paper. Using this base for growing new cells would assure the correct physical orientation of the cells and would be easy to work with in a clinical setting.

"We realize that retinitis pigmentosa, another significant retinal degenerative disorder could potentially benefit from this type of technology. This is a disorder that affects perhaps 100,000 people in the United States and certainly more than 1.5 million people worldwide. Some type of autologous transplantation of retinal cells, facilitated by Bucky Paper, could be an important therapeutic strategy for RP, as well," Loftus said.

Loftus concedes that commercial versions of the Vision Chip and the autologous transplantation using Bucky Paper is still several years away. For more information, contact NASA's commercial technology office at dlackner@mail.arc.nasa.gov.

Loftus presented the findings on December 6, 2002 at a conference organized and hosted by the Girvan Institute of Technology. The event was held at the NASA Ames Moffett Training and Conference Center at Moffett Field.