Interview with Robert Greenberg

HH/Beck: Hi Dr. Greenberg. Thank you for time today.

Greenberg: Hi. Dr. Beck, my pleasure.

HH/Beck: I know that youre one of the pioneers involved with Second Sight, which is a company developing implants for vision. But before we get into the discussion, 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, thats fine. 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 my responsibility was to evaluate medical devices.

HH/Beck: Can you tell me about your Ph.D. work please? What was your dissertation about?

Greenberg: My dissertation was in biomedical engineering and it was on the theoretical analysis of electrical stimulation of the retina so it was very much along the lines of the work were doing now. However, the dissertation was theoretical in nature, and of course Second Sight is focused on the real world and pragmatic approach to the same topic.

HH/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, they are one of the leading companies in cochlear implants.

HH/Beck: I think many of us have been anxiously waiting for someone to apply cochlear implant technology to vision and it seems like you are on the threshold of getting that done.

Greenberg: Yes, I think the technology and research from cochlear implants has been very useful for us, and has allowed us to start with a strong knowledge base which applies and overlaps in some respects to the visual system.

HH/Beck: What would be the best overview or general description of Second Sight and their goals?

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, and there are approximately 3 million of these people in the western world. These people have intact optic nerves, but their retina is damaged.

HH/Beck: So that is similar to cochlear implants in the sense that both devices depend on the sensory cranial nerve being intact, with damage or dysfunction limited to the sensory end organ, either the cochlea or the retina. Please excuse my ignorance, but I know very little about the eye beyond rods perceiving black and white and cones perceiving color! Is the eye set up topographically, much like the ear is set-up tonotopically?

Greenberg: Yes, that is essentially correct. And that is probably the anatomic and physiologic key to success, as we depend on being able to stimulate certain parts of the retina, in order to produce certain visual images. The retina is spatially keyed, so that when you stimulate a particular location on the retina, the patient perceives a spot of light at that location. So the goal is to present an array of electrodes to the retina to build a perception that allows the patient to visually perceive the image made up of many spots like the scoreboard at a baseball stadium.

HH/Beck: I recall that with cochlear implants we had more than a decade or two 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 do you think are necessary do give a realistic visual image to the patient?

Greenberg: No one really knows, but our goal is 1000 contact points and if those are each individually discernable points, I think well be able to restore vision very adequately. We can physically make electrodes with thousands of contact points at this time, but were still in the early stages of development, and most of the work at this time is monocular (one eye) and most of it is black and white perception though we expect to be able to also produce color vision in the not too distant future.

HH/Beck: In the hearing 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? I mean, 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 that the patient can get with one eye, without perceiving the true and full 3D image.

HH/Beck: Where are you in terms of clinical trials at this time?

Greenberg: We have two FDA clinical trials occurring at the moment. The first involves a device which is similar to a cochlear implant, and we call it the ARGUS 16 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 is the worlds first retinal prosthesis capable of producing multiple spots of light.

HH/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, 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 because theyve been down this road before, that helps us better understand where we are and where we want to go. Regarding the hardware, what we have is an implant that has been implanted behind the ear, and has been placed there by an otologist, and then wires that are the width of a human hair are tunneled through to the eye by an orbital-facial surgeon and the electrode array is placed inside the eye, on the retina by two vitreo-retinal surgeons. Our second-generation device, which is more compact, is being bench tested as we speak.

HH/Beck: So for the early model you had four surgeons, the otologist and the orbital-facial surgeon and the vitreo-retinal surgeons, and everything was subcutaneous (below the skin), and there are no visible wires?

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.

HH/Beck: This is really amazing. How many patients have you implanted at this time?

Greenberg: We have implanted only two patients, and the first is about six months post-op.

HH/Beck: Can you tell us anything about their visual perceptions?

Greenberg: We havent released the outcomes yet, but hope to soon. I can tell you the patients are pleased and very excited about the system.

HH/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 third patient. As you can imagine the engineering takes time, and of course the rehabilitation and the post-op work takes tremendous time too. As far as FDA approval, were probably a few years away from that before youll see a commercially available product, assuming everything goes well!

HH/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.

HH/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, CLICK HERE

Click here to visit the Advanced Bionics website.

For More information about Second Sight, CLICK HERE