Beck: Hi Dr. Greenberg. Thank you for time today.
Greenberg: Hi. Dr. Beck, my pleasure.
Beck: I know youre one of the pioneers involved with Second Sight, which is a company developing implants for vision, but before we get into the topic at hand, if you dont mind, Id like to start with a little biographical information about you, so the readers will know who you are!
Greenberg: Sure. I went to medical school at Johns Hopkins, and did my Ph.D. graduate training there too. I finished my Ph.D. in 1996 and graduated from medical school in 1998. After completing my MD I went to work at the FDA as a medical officer and it was my responsibility to evaluate medical devices.
Beck: Can you tell me about your Ph.D. dissertation please?
Greenberg: My dissertation was in biomedical engineering regarding the theoretical analysis of electrical stimulation of the retina so it was very much along the lines of the work Im doing now. However, the dissertation was theoretical in nature, and of course Second Sight is focused on the real world and has a pragmatic approach to the same topic.
Beck: When did Second Sight begin?
Greenberg: Second Sight was incorporated in 1998 and really got going in 1999. The company was founded by Alfred Mann, and as you know Doug, Mr. Mann was also the founder of Advanced Bionics, one of the leading companies in cochlear implants.
Beck: Yes, I had the honor of meeting him a year or two ago. I think many of us have been waiting for someone to apply cochlear implant technology to vision, and it seems like Second Sight is actually making that happen.
Greenberg: Yes, the technology and research from cochlear implants has been very useful for us, and allowed us to start with a strong knowledge base which does apply and overlap in some respects to the visual system.
Beck: What would be the best overview or general description of Second Sight?
Greenberg: The mission of Second Sight is to restore vision for patients who have been blinded by outer retinal degenerations, such as; macular degeneration and retinitis pigmentosa, There are approximately 3 million of these people in the western world. They have intact optic nerves, but their retina is damaged.
Beck: So thats similar to cochlear implants in the sense that both devices depend on the cranial nerve being intact, with damage or dysfunction limited to the sensory end organ, either the cochlea or the retina. Is the eye set-up topographically, much like the ear is set-up tonotopically?
Greenberg: Yes, thats essentially correct. And I believe that is probably the anatomic and physiologic key to success. We depend on being able to stimulate certain parts of the retina to produce visual images. The retina is spatially keyed, so when you stimulate a particular location on the retina, the patient perceives a spot of light at that location. The goal is to present an array of electrodes to the retina to build a visual perception that allows the patient to visually perceive the image.
Beck: With cochlear implants weve had decades of discussion to figure out how many electrodes (i.e. contact points) were necessary to allow open set speech recognition, and in many respects, that discussion still goes on. How many contact points are necessary to present a realistic visual image to the patient?
Greenberg: No one really knows. One of the things that surprised us, is how well patients have performed with as few as 16 contact points along the retina. Patients have been able to read large letters and identify objects with these very few contact points. Our ultimate goal to provide excellent vision is still 1000 electrodes, as I mentioned to you a few years ago, but we now believe that useful vision can be obtained with significantly fewer electrodes. We can currently produce electrodes with a few dozen contact points at this time, and were still in the early stages of development of higher resolution devices. Most of the work at this time is monocular (one eye) and most of it is based on black and white perception -- though we expect to be able to produce color vision in the not too distant future.
Beck: In the auditory world, we can say with reasonable certainty that with one ear hearing, one cannot truly get localization, is that the same with the visual system? That is, with monocular vision, can the patient perceive depth perception?
Greenberg: With one eye you cannot get the true 3-D visual cues, but there are some figure-ground hints the patient can get with one eye, without perceiving the true and full 3D image.
Beck: Dr. Greenberg, where are you in terms of clinical trials at this time?
Greenberg: We have four patients who have been implanted at this time. All three patients have a device which is similar in some respects to a cochlear implant. The device is called it the ARGUS 16 (or the Model One) after the all-seeing mythological god of the same name. It is a crude device in some respects. It has only 16 contact points but it is the worlds first retinal prosthesis capable of producing individually controllable multiple spots of light.
Beck: What about the hardware? In the early days of cochlear implants we had a processor that was the size of a pack of cigarettes, and we had wires to and from the processor, which went to and from the microphone and the external coil, and the signal was sent across the skin via electromagnetic information. Is that similar to the visual device?
Greenberg: Yes, the system is indeed similar. Of course cochlear implants started in the analog days, and were starting visual implants in the digital age. The digital advantage is enormous, so our technology is more flexible, and of a higher quality regarding the electrical and engineering systems. Of course, we have a very close relationship with our sister company, Advanced Bionics, and theyve been down this road before. Advanced Bionics R and D helped us better understand where we are and where we want to go. Regarding the actual hardware, what we have is a device behind the ear, placed there by an otolaryngologist. The wires are the width of a human hair and they are tunneled through to the eye by an orbital-facial surgeon, and then the electrode array is placed on the retina by two vitreo-retinal surgeons. Our second-generation device, which is more compact, is being biologically tested and electrically bench tested as we speak.
Beck: Can I assume that the entire device is subcutaneous (below the skin), and there are no visible wires or electronics?
Greenberg: Yes, thats correct. However, as this evolves well quickly have systems that will be placed entirely in the eye, requiring only the retinal surgeons.
Beck: This is really amazing technology! Can you tell us anything about the visual perceptions the four patients have experienced?
Greenberg: I can tell you the patients are pleased and very excited about the system. I should mention that of these four people, one was totally blind and the other three could just barely discern light. With the device, the patients can discern spatially distinct spots of light and they can also locate and identify objects, such as a plate versus a knife or a cup on a table in forced choice tests. They can also read large letters, such as a 12 inch letter from arms length selected from a subset of letters.
Beck: When do you anticipate implanting the next individual? And while were talking about timelines, can you gaze into your crystal ball and give me any idea as to when this might be ready for FDA approval?
Greenberg: Probably over the next few months well be implanting the next patient. As you can imagine, engineering and rehabilitation takes tremendous time. As far as FDA approval, were probably a few years away from a commercially available product, assuming everything goes well, but were getting closer every day.
Beck: Thanks Dr. Greenberg. This is an amazing science, and even though its a little beyond our normal interview topics regarding hearing healthcare, I think most of the hearing healthcare professionals and patients, and their families are very interested in this topic, and I appreciate your taking the time to discuss this with me.
Greenberg: My pleasure Dr. Beck. Thank you for the invitation and the opportunity too.
Beck: I hope well be able to get together next year for an update?
Greenberg: That would be fine. Lets do that.
HH/Beck: Thanks Dr Greenberg.
For more information about the Alfred Mann Foundation, visitwww.aemf.org.
For More information about Second Sight, visit www.2-sight.com.
Beck: Hi Dr. Greenberg. Thank you for time today.