AGlimpse Into the Future Because of the Cochlear Implant

[Guest guest]

An interview from Healthy Hearing, May 31, 2004. The interviewer is L.

Beck, Au.D.

......................

Greenberg, M.D., Ph.D., President and CEO of Second Sight

Topic: Restoring Vision via IMPLANTS

Greenberg, M.D., Ph.D., President and CEO of Second Sight

TOPIC: Restoring Vision via IMPLANTS5-31-2004

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

Greenberg: Hi. Dr. Beck, my pleasure.

HH/Beck: I know you’re 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 don’t mind, I’d 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 s 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.

HH/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 I’m 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.

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, one of the leading companies in cochlear

implants.

HH/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.

HH/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.

HH/Beck: So that’s 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, that’s 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.

HH/Beck: With cochlear implants we’ve 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

we’re 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.

HH/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.

HH/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 world’s first retinal

prosthesis capable of producing individually controllable 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 we’re 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

they’ve 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.

HH/Beck: Can I assume that the entire device is subcutaneous (below the

skin), and there are no visible wires or electronics?

Greenberg: Yes, that’s correct. However, as this evolves we’ll quickly

have systems that will be placed entirely in the eye, requiring only the retinal

surgeons.

HH/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 arm’s length selected from a subset of letters.

HH/Beck: When do you anticipate implanting the next individual? And while

we’re 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 we’ll be implanting the next

patient. As you can imagine, engineering and rehabilitation takes tremendous

time. As far as FDA approval, we’re probably a few years away from a

commercially available product, assuming everything goes well, but we’re getting

closer every day.

HH/Beck: Thanks Dr. Greenberg. This is an amazing science, and even though

it’s 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 we’ll be able to get together next year for an update?

Greenberg: That would be fine. Let’s do that.

HH/Beck: Thanks Dr Greenberg.