Scientists have been working for decades to create an optical prosthesis that restores at least partial vision to those suffering from retinitis pigmentosa, macular degeneration and other retina-damaging diseases. Some retinal implants have begun to deliver on that promise, but the challenge remains for researchers to develop a technology that, in addition to providing clear images, can be worn comfortably over the long term.

Germany's Retina Implant, AG, thinks it has made great strides in both areas, an assertion that will be put to the test later this year when the company launches its second clinical trial, placing subretinal (under retina) implants in about 50 patients over the next few years. Meanwhile, Sylmar, Calif.–based Second Sight Medical Products plans to make its epiretinal (over retina) implants commercially available in Europe later this year. Researchers at the Massachusetts Institute of Technology and other institutions and medical technology companies are likewise developing retinal implants—the retina lines the eye's inner surface and records images in patterns of light and color—but are not as far along as Retina Implant or Second Sight.

Retinal reawakening
Retina Implant's initial human clinical trial, started in 2005, improved the eyesight of 11 patients to the point where they were able to recognize objects as well as see shapes so clearly they could combine individual letters to form words or, essentially, read at a basic level at normal reading distance and in regular light conditions, says Eberhart Zrenner, the company's co-founder and director and chairman of the University of Tübingen's Institute for Ophthalmic Research in Germany. Zrenner presented the trial's results in May at the 2010 Association for Research in Vision and Ophthalmology's annual meeting in Fort Lauderdale, Fla.

Retina Implant's second clinical trial seeks to implant the latest version of the company's technology in a larger pool of patients. The new implant no longer has external parts—its power supply is positioned under the skin behind the ear, connected with a thin cable that leads to the eyeball so that the chip does not move once implanted. (This could damage the chip.)

Retinitis pigmentosa kills the retina's photoreceptors, which are the rod and cone cells that convert light into electrical signals for the brain, leading to vision loss. This disease, one of the most common forms of inherited retinal degeneration, affects about one in 4,000 people in the U.S. Age-related macular degeneration (AMD), a leading cause of vision loss in the U.S. among people 60 years and older, gradually destroys sharp, central vision. The macula (the light-sensitive retinal tissue at the back of the eye) degenerates in two ways: In "dry" AMD the macula's light-sensitive cells slowly break down; in the "wet" form abnormal blood vessels behind the retina start to grow under the macula, thereby displacing it.

Retina Implant's device is a three- by three-millimeter microelectronic chip (0.1 millimeter thick), containing about 1,500 light-sensitive photodiodes, amplifiers and electrodes that is implanted directly under the retina to generate artificial vision by stimulating inner retina nerve cells. The chip, which is placed in the retina's macular region, absorbs light entering the eye and converts it into electricity that stimulates any still-functioning retinal nerves. This stimulation is relayed to the brain through the optical nerve.

It takes the brain one or two days to adapt to chip-assisted vision, according to Zrenner. "Lines are typically all that can be expected to be seen initially by people with retinal implants," he says. "However, scientists are finding that the human brain can quickly retrain itself to interpret the lines and shapes of different gray levels into meaningful images." With the aid of a chip one Retina Implant patient reported seeing images and words slightly flickering as though they were viewed through small waves at the bottom of a pool, Zrenner adds.

4 Comments

1. 1. femtobeam 08:00 AM 6/16/10

   This is a way to give sight to the blind, see through a person with wireless access, or combine it with laboratory grown braincells to produce a visual cortex equivalent for a robot.
   
   Combinations are "Cyborgs", which we all are becoming now.

   Reply | Report Abuse | Link to this

2. 2. sandraonley 03:48 PM 7/28/10

   My grandson who is 9 has just been diagnosed with cone rod dystrophy. He is under the care of doctors at Duke Eye Center in North Carolina. Can this new discovery possibly help him in the future.

   Reply | Report Abuse | Link to this

3. 3. LINDA 08:04 PM 8/24/10

   MY FATHER SUFFERS WITH FUNDUS FLAVIMACULATUS STARGARDT DISEASE, ALMOST 15 YEARS AGO, RIGHT NOW HE IS 67, DO YOU THING THE RETINA IMPLANT IS AN OPTION IN HIS CASE ? OR THERE IS ANOTHER STUDY THAT HELP HIM TO IMPROVE HIS VISION?

   Reply | Report Abuse | Link to this

4. 4. billenglish 09:14 PM 9/17/10

   Nanotechnology could produce a light powered chip so tiny, that tens of thousands of independent retinal implants could be 'shot' into place in the retina, by a process needing R&D. Such would need no wires to external power source, could restore vision to entire retina instead of 10 X 10 mm square, would also be permanent, and require no radical surgery to implant. Light needs to be sensed, an electric signal can be generated from light, optic nerves can be thus stimulated. The surface of implants would conduct electric signals to those nerves. A means to 'shoot' them uniformly to a very shallow depth in retina wall with one short office visit, might avail itself one day. But even if requiring several treatments at intervals pending development of a one treatment method, the intense need should inspire nanotechnology buffs to work on this prospect. It may be simpler to achieve than I would know about, not being up to date on the subject. I would like to know if it is being developed already and if not, why? We tire of all these gadgets that do nothing but entertain us, when researchers as myself are pounding sand into rat holes, attempting to develop modern assist devices for the handicapped. With so little help from the techno geeks, I myself am now struggling to develop my 'Sense organs synthesizer', Patent Applied for in 2002. Were it not for my grateful collusion with Dr. Peter Meijer, I might not stand a chance of completing a prototype. We are now attempting to create a nonprofit organization, so we may apply for grants, so we may fund R&D toward this end. We only need to 'interface' Dr. Meijer's vOICe system, which "paints a sound scape" of a real-time view for the blind, for my adaptation of adding a linear tactile array. This will give me 'proof of concept' for my approach, to inspire funding for full R&D toward a production model.
   
   To see Dr. Meijer's invention go to seeingwithsoud.com and opt for the online demonstration. If my tactile array option works well, Dr. Meijer has full permission to use it. He would then be the source for this form of tactile representation of real time visual display for the blind until my SOS Device ('Sense organs synthesizer') is in production. As it is, I see his invention as far superior to devices costing $10,000 or more and it costs far less to set up. A web cam on headband, laptop with his software, and earphones, are all one needs to have a 'sound scape' of real visual information for the blind. It takes practice, but it works.
   
   All My best,
   
   Bill English

   Reply | Report Abuse | Link to this