Advances in the Use of Electronic Devices to Restore Vision
Report from the annual ARVO (Association for Research in Vision and Ophthalmology) meeting
May 5, 2011 - Posters and papers presented at the 2011 ARVO Conference demonstrate that advances continue in the development of prosthetic devices to restore vision to people with retinal degenerative diseases. More than 50 posters were presented at a session on retinal prosthesis. Included in this group were presentations of studies sponsored by both Second Sight and Retina Implant AG, the two companies that currently are testing such devices in human subjects.
The Argus II – Second Sight
The Argus II device was approved for sale in Europe earlier this year. It works by converting video images captured from a miniature camera, housed in the patient’s glasses, into small electrical pulses, which are transmitted wirelessly to electrodes on the front surface of the retina. These electrodes bypass the damaged photoreceptors; they stimulate the retinal cells that send electrical signals to the brain, where they cause glowing and flashing sensations. Although these are quite different from normal visual sensations, with appropriate training, patients learn to interpret them, thereby gaining some functional vision. In addition to the glasses and camera, people using this device must also wear an external power pack.
A clinical trial of the Argus II has been ongoing in 10 centres around the world for more than four years. Dr. Mark Humayun of the University of Southern California presented results at the ARVO conference. He noted that all of the people implanted with the device had only “bare light perception or worse vision, due to retinitis pigmentosa (RP) or related outer retinal degenerative disease,” when beginning the trial.
“All 30 subjects in the trial obtained visual perceptions from the device,” says Dr. Humayun. “A large majority of them experienced benefit from the system in terms of visual function tests that ranged from localizing and identifying an object to grating visual acuity [distinguishing a patch of alternating black and white lines from a patch of uniform gray]. Functional vision orientation and mobility tests demonstrated that the treated subjects were significantly better at performing visual tasks such as following a line or finding a door, with the system ON vs. OFF. These gains in vision were maintained by many subjects during long-term follow-up (i.e. > 2 years)."
Dr. Humayun also reported on research conducted by Dr. Paulo Stanga, from Manchester, UK, which showed that subjects fitted with Argus II were able to perceive colours consistently.
"We were delighted to observe, for the first time ever, that nine participants were able to reliably and repeatedly perceive up to eight different colours using Argus II", said Dr. Stanga. "Colour perception could be achieved by precisely controlling aspects of the electrical stimulation.”
Subretinal Implant - Retinal Implant AG
A number of findings from the second clinical trial of the Retinal Implant AG device were also presented at ARVO. This was the first trial of this product in which the device was implanted permanently.
The tiny device is implanted beneath the retinas of people who have completely lost their sight. Once implanted in the eye, the device captures seven images per second and sends electronic pulses to the retina through 1500 tiny needle-like electrodes, to produce visual sensations – essentially substituting for the role of the person’s damaged or lost photoreceptors. No glasses or external camera are necessary, but the initial model of this device required an external power source, which was usually worn behind the ear.
One of the presentations at ARVO described the successful testing of an updated Retinal Implant AG device with a new wireless power source - a sub-dermal coil implanted under the skin. This device has so far been tested in seven people. The participants were able to identify geometrical shapes, the hands of the clock, and the parts of a common place-setting at a table. Although color vision is not possible, the subjects differentiated 7 to 10 shades of grey; and they showed increased sensitivity for infrared light, resulting in a shifted brightness perception. They could also move freely throughout the activities of their day, because the new power source did not get in their way.
“This study proves that the technology can work well, while offering patients the mobility and the freedom to see beyond the laboratory setting,” says the CEO of Retinal Implant AG, Dr. Walter-G. Wrobel. “We look forward to presenting additional data in the future, as more patients receive implants in Germany and beyond.” In March, Retina Implant AG announced that it would begin the first North American trials of this device at the Wills Eye Institute in Philadelphia.
Retinal Implant AG investigators also reported at ARVO on a successful surgical replacement of one of these devices. After the first implanted device failed, surgeons used it to guide their placement of the new one. The research team reported that the exchange procedure was far easier than the initial implantation process, and that the substitute could be placed exactly in the same position. No adverse reaction occurred. The ability to replace these devices safely and easily when they fail, without having to teach the patient’ how to use them all over again, will be important to their long-term use.
Several other groups are also working to get their own versions of retinal prostheses ready for human trials. This promises to be a busy area of research in years to come.
ARVO Presentations
Subretinal Active Electric Implants In Blind Patients. Transchoroidal Surgery - First Surgical Implant Exchange. Presented Wednesday May 4, 2011. Helmut G. Sachs, Karl Ulrich Bartz-Schmidt, Florian Gekeler, Dorothea Besch, Ursula T. Brunner, Barbara Wilhelm, Walter Wrobel, Veit-Peter Gabel, Eberhart Zrenner.
Improvement of Visual Orientation and Daily Skills Mediated by Subretinal Electronic Implant Alpha IMS in Previously Blind RP Patients. Presented Sunday May 1, 2011. Eberhart Zrenner, A. Bruckmann, U. Greppmaier, G. Hoertdoerfer, C. Kernstock, I. Sliesoraityte, K. Stingl, B. Wilhelm.
Vision Mediated by the Subretinal Implant: Improvement for Activities of Daily Living - Preliminary Results. Presented Sunday May 1, 2011. Katarina Stingl, Gernot Hörtdörfer, Udo Greppmaier, Anna Bruckmann, Barbara Wilhelm, Walter Wrobel, Ieva Sliesoraityte, Eberhart Zrenner.
Interim Performance Results from the Second Sight® ArgusTM II Retinal Prosthesis Study. Presented Tuesday, May 03, 2011. Mark S. Humayun, L da Cruz, Gislin Dagnelie, Jose A. Sahel, Paulo E. Stanga, Eugene Filley, Dean Eliott, Jacque L. Duncan, Robert J. Greenberg.
Patients Blinded By Outer Retinal Dystrophies Are Able To Perceive Color Using The ArgusTm II Retinal Prosthesis System. Wednesday, May 04, 2011. Paulo E. Stanga, Farhad Hafezi, Jose A. Sahel, Lyndon daCruz, Francesco Merlini, Brian Coley, Robert J. Greenberg, Argus II™ Study Group.