Artificial vision research builds to a ‘critical mass’

Teams around the world are developing devices to simulate vision in blind patients. A device could be on the market within a few years, some believe.

Retinal implants that enable blind individuals to see light and simple patterns, and even to regain lost visual function, are in clinical trials, and one or more could become commercially available within several years, according to researchers.

The field of artificial vision research continues to grow, and a market-approved device may be nearer to reality than many clinicians realize, said George A. Williams, MD, in a telephone interview with Ocular Surgery News. Dr. Williams, an OSN Retina/Vitreous Section Member, is also a member of the board of the Detroit Institute of Ophthalmology, which sponsored the fourth biennial World Congress on Artificial Vision: The Eye and the Chip 2006. The event, held in Detroit, showcased developments in artificial vision with presentations by leaders in the field.

Dr. Williams said research into artificial vision and industry development in the field have expanded substantially since the congress was first held in 2000, proof that continued advancements have generated further research. He said he anticipates that a retinal implant device for artificial vision could become commercially available within 3 years.

“I think we’re now at the point where we really have a critical mass of investigators,” Dr. Williams said. “In any field, it takes a while to develop enough people who are interested in it, and now we have that interest. That’s why I’m so optimistic that we’re going to see much improved progress over the next few years.”

Artificial vision field outlook

Several groups, working separately, are in the process of investigating a number of technologies for artificial vision in blind patients or patients with low vision, according to Dr. Williams. The goal of artificial vision research has been to restore ambulatory vision, Dr. Williams said, so that patients can independently navigate and ambulate in unfamiliar situations.

He said the first generation of such devices has been designed mainly for patients who have no useful vision. Patients currently involved in clinical trials of these devices typically have inherited retinal diseases such as retinitis pigmentosa that cause reduced vision.

Technologies under investigation include epiretinal implants, electronic devices that sit on the front surface of the retina; devices implanted in the subretinal space; and devices that directly simulate the optic nerve.

Dr. Williams said that in the future, continued improvements in the field could restore visual function and even some reading vision.

“It’s a very exciting time for the continued development of artificial vision,” Dr. Williams said. “We now have active programs in virtually every major country, including the United States, Japan and Germany. As a result, we expect that we’re going to see continued progress.”

There are a number of devices in development and in clinical trials. For this article, Ocular Surgery News spoke to researchers investigating two devices that have reached the stage of human clinical investigations.

The Artificial Silicon Retina chip is implanted in the subretinal space and powered by incoming light that produces a small current that operates the device. Image: Chow AY
Closeup of the ASR implant. Image: Chow AY	The IMI 49-electrode retinal stimulator sends visual data through gold wires to a small electrode array implanted on the retina. Image: Zehnder

Learning Retinal Implant

One of the devices on the forefront of the artificial vision technology wave, according to Dr. Williams, is the Learning Retinal Implant, being developed by the Swiss company Intelligent Medical Implants AG and its subsidiary, the German-based IIP-Technologies GmbH.

Thomas Zehnder, PhD, chief medical officer and industrial engineer for IIP-Technologies, said in a telephone interview with Ocular Surgery News that the Learning Retinal Implant has been successfully implanted in four patients, two with 6 months follow-up and two with 4 months. The subjects have participated in stimulation sessions since their implantations, which help them learn to use the device.

“The patients had been completely blind for more than 10 years, and they must get used to seeing again,” Dr. Zehnder said. “We walk through different sequences of training sessions. We actually do overall, according to study protocol, 20 sessions, which take half a day, per patient. The longer you train them, usually the better they can recognize objects and the movement of objects.”

He said patients can detect lines and points being moved in different directions. A study performed with a single electrode version of the device showed that 19 out of 20 formerly totally blind patients could see a small point of light.

The company will start key clinical trials in Europe in 2007 and in the United States in mid-2007, Dr. Zehnder said. If the device receives CE Mark certification in Europe, it could be on the market there by 2008, he said. If U.S. clinical trials stay on track and the device receives Food and Drug Administration approval, the device could be on the U.S. market by 2009, he estimated.

How the implant works

Thomas Zehnder

The Learning Retina Implant system has three components, according to Dr. Zehnder. The core component is the implant, a retinal stimulator that is implanted in the eye. The second component is the Pocket Processor, a battery source and image processing computer, which is worn at the patient’s waist. The third component is the visual interface, a pair of spectacles with a camera and transmitter.

The camera captures information from the surrounding environment and sends it to the Pocket Processor, which converts the information into stimulation commands. The stimulation commands are sent to the implant and converted into electrical impulses that stimulate the retina directly.

The impulses from the 49-electrode implant to the retinal nerve cells approximate a healthy retina’s response, Dr. Zehnder said.

“With everything we were able to do with simple pattern stimulation, we have achieved all our internal goals,” he said. “The next step – and this is very important to the learning process of the patient – is to have a camera view, so that you have a real-time image processing, because only when the patient sees the object, can actually touch the object, can take the object in his hand and move it around in front of his camera spectacles and put all these things together – his experience from seeing and feeling – that’s where the important learning curve will come into play.”

The criteria for patient selection are strict, so that the implant can achieve maximal functionality, he said. Patients must have intact nerve tissues, including the ganglion cells. Those cells are stimulated to fire by electrical pulse sequences from the implant, so the device essentially takes over the function of the rods and cones, he said. The optic nerve must also be fully intact and the visual cortex must be fully developed and undamaged.

The device is currently being used in patients with retinitis pigmentosa, Dr. Zehnder said. Patients’ ages range from 20 to 75 years old. Dr. Zehnder said age has not been a factor in selecting patients.

Artificial Silicon Retina implant

The Artificial Silicon Retina implanted in an eye with retinitis pigmentosa. The chip does not require wires, but works by stimulating the surrounding retina cells to power the implant. Image: Chow AY

The U.S. corporation Optobionics is investigating a different wireless retinal implant approach, a chip called the Artificial Silicon Retina. Researchers implanted the device in 10 patients with retinitis pigmentosa between 2000 and 2006 as part of an FDA feasibility and safety study. Those patients have not had problems with rejection or infection, said researcher Alan Y. Chow, MD, a co-founder of Optobionics with his brother, Vincent Chow, MD.

In 2005, the microchip was implanted in 20 more patients in a FDA-approved expanded study. In a telephone interview with Ocular Surgery News, Dr. Chow said initial results in those patients have been released, and full 1-year follow-up results are expected to be reported later this year. Of the first 10 patients in this group of 20, nine have experienced moderate to substantial improvements in visual function, with improvements in visual acuity, contrast sensitivity, size of visual field and color perception, Dr. Chow said.

Patients have also experienced improvements in “darkness” perception, Dr. Chow said. He and his colleagues discovered that after patients lose vision, “sight” becomes a constant light grey, whether the blind person is in dark or light environments. As patients’ vision improves, they begin noticing that night becomes dark again and day becomes light, he said.

Some patients in the study had adequate central vision but extremely small visual fields, sometimes less than 2° or 3°, before the chip implant, Dr. Chow said. Other patients have lost visual field and their central vision has decreased to hand motions or light perception vision. Patients in the study are on average 30 years old, he said.

Dr. Chow said Optobionics hopes to expand the use of the device to younger patients as development progresses.

How the implant works

Alan Y. Chow

The Artificial Silicon Retina is implanted into the subretinal space, Dr. Chow said. The chip is powered by incoming light and produces a small amount of electrical current, which stimulates the surrounding retinal cells. The wireless device does not require an additional power source.

Initially, researchers thought the chip would produce an image similar to a pixel-by-pixel display on a computer screen, allowing patients to see their surroundings, Dr. Chow said. As research progressed, they learned that that assumption was incorrect.

“We discovered that the predominant and most exciting effect of the chip was that the chip was stimulating the remaining retinal cells to begin functioning on their own, a neurotrophic effect of the chip,” Dr. Chow said. “As a result of that, the vision that is returning is the vision that one lost. In other words, color vision and contrast perception and visual acuity. These are visual functions that cannot be mimicked by direct simulation. It really has to be from the return of the natural function itself.”

For more information:

• George A. Williams, MD, can be reached at 3535 West 13 Mile Road, Royal Oak, MI 48073; 248-288-2280; e-mail: gwilliams@beaumont.edu.
• Thomas Zehnder, PhD, can be reached at Intelligent Medical Implants AG, Industriestrasse 24, CH-6302 Zug, Switzerland; 41-41-723-3838; fax: 41-41-723-3839; e-mail: thomas.zehnder@intmedimplants.com.
• Alan Y. Chow, MD, is an assistant professor at the Rush University Medical Center. He can be reached at 386 Pennsylvania Ave. 3N, Glen Ellyn, IL 60137-4323; 630-858-4411; e-mail: AlanYKC@aol.com.

• Optobionics Corporation, maker of the Artificial Silicon Retina chip, can be reached at 850 East Diehl Road, Suite 120, Naperville, IL 60563-9386; 630-245-0600; fax: 630-245-0601; Web site: www.optobionics.com. Intelligent Medical Implants AG, maker of the Learning Retinal Implant, can be reached at Industriestrasse 24, CH-6302 Zug, Switzerland; 41-41-723-3838; fax: 41-41-723-3839; Web site: www.intmedimplants.com; e-mail: info@intmedimplants.com.

• Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.