The Retinal Prosthesis for the Blind October, 2012 Shawn K. Kelly, - - PowerPoint PPT Presentation

The Retinal Prosthesis for the Blind

October, 2012 Shawn K. Kelly, PhD

VA Center for Innovative Visual Rehabilitation Carnegie Mellon University

The Retinal Prosthesis

An electronic implantable device to restore functional vision to patients with certain forms of blindness, primarily retinal degenerative diseases. The device works by stimulating nerves in the visual system based on an image from an external camera.

Anatomy of the Eye

Anatomy of the Retina

Direction of Light Inside/ Front Outside/ Back

Sending Images to the Brain

Degenerative Diseases

• f the Outer Retina
• Age-related Macular Degeneration (AMD)

– Loss of photoreceptors in macula (center), working outward – Strikes at age 60-80 with increasing incidence – May take decades to go blind – 2 (?) million cases in US, tens of millions worldwide

Degenerative Diseases

• f the Outer Retina
• Retinitis Pigmentosa (RP)

– Loss of photoreceptors in periphery, working inward – Genetic, strikes at age 15-60 – Typically a decade or less to go blind – 100,000 cases in US, 1.7M worldwide

Living with RP

The Boston Retinal Implant

• Electronic prosthesis to restore functional

vision to patients with retinitis pigmentosa and age-related macular degeneration

• 20-year collaboration: MIT, MEEI, VA,

Cornell, Carnegie Mellon, and others

Subretinal Implant Placement

Direction of Light Inside/ Front Outside/ Back

Retinal Prosthesis Function

• Electrically stimulates ganglion nerves based on an

external camera image

Image Processing Power And Data Transmission

Other Visual Prostheses

Epiretinal Cortical

Visual Prosthesis Research Worldwide

Optic Nerve Cortical Retina Epi Retina Sub

Challenges

• Surgical

– Place electrode array safely and securely – Place electronics where they won’t cause damage

• Microfabrication

– Electrode materials that can safely deliver needed charge but not physically damage tissue – Water-tight packaging of electronics

• Electrical Engineering

– Deliver balanced electrical current to electrodes – Wirelessly deliver power and image data to implant

• Image Processing

– Intelligently downsample camera images to 256 pixels – Convey saliency, maximum information about environment

Short-term Human Proof-of-concept Trials

• 1998 – 2000, Surgical trials on six

volunteers

• Epiretinal stimulation for a few hours
• Reported spots, lines, not complex shapes

Rizzo, et al. IOVS, 2003 Rizzo et al. IOVS, 2003

Portable, 100-channel Neural Stimulator

Short-term Human Proof-of-concept Trials

Video - surgery

Short-term Human Proof-of-concept Trials

Video - clouds

Short-term Human Proof-of-concept Trials

Video - spots

What We Learned

• This concept works – patients can see

spots and lines, distinguish from control

• We need to develop a chronic implant

to allow patients to learn

• A number of new technologies needed

to be developed for chronic implantation

Wireless Power and Data

Power and data are delivered by inductively coupled coils via magnetic fields

Miniaturize: Integrated Circuit Design

Custom chip design is labor-intensive, but necessary given our size and power restrictions

Kelly, et al. IEEE ISSCC, 2004 Theogarajan et al. IEEE ISSCC, 2006 Kelly, et al. IEEE TBioCAS, 2011 Theogarajan IEEE JSSC, 2008

First-Generation Implant

• Implanted in 3 minipigs for up to 10 months in

2008

• Wireless power and data telemetry
• Coated in silicone – viable for many months, not

decades

Shire, et al. IEEE TBME, 2009

Improvements to First Generation Implant

• Hermetic barrier to protect circuits
• Larger telemetry coils
• Easier surgical access for electrode

insertion

Second Generation Implant Ab externo approach

• Electrode array enters the space under the

retina through the scleral wall of the eye.

Hermetic Titanium Case

• Ceramic 19-pin hermetic feedthrough
• Curved titanium case
• Laser-welded top and bottom lids

Sputtered Iridium Oxide Film Electrodes

• Higher charge capacity
• 1 to 6 mC/cm2
• Pt is limited to 100 µC/cm2
• But the Shannon Limit is still in effect!

Prototype Implant

In vivo Results

• Recorded artifact of current

pulses from cornea – shows implant was working

• Waveform is measured at

implant and telemetered out

• Noisy, but you can see the

step-ramp components, and variation of voltage with current

Kelly, et al. IEEE ISABEL, 2009 Kelly, et al. IEEE TBME, 2011 Kelly, et al. IEEE EMBC, 2009 Kelly, et al. BSPC, 2011

Third Generation Prosthesis

• Hundreds of channels (>256)
• Smaller hermetic case
• Stimulator chip and electrode array under

development

Image Processing

Future Research

• Finish 256+-channel retinal prosthesis,

prepare for FDA clinical trials

• Design external camera system, portable

telemetry system, etc.

• Image processing to convey maximum

information with 256 pixels.

The Boston Retinal Implant Project

Engineering

• John L. Wyatt, PhD (MIT)
• Douglas B. Shire, PhD (VA, Cornell)
• Shawn K. Kelly, PhD (VA, CMU)
• Ashwati Krishnan, MS (CMU)
• Marcus Gingerich, PhD (VA, Cornell)
• Attila Priplata, PhD (VA, MIT)
• William Drohan, MS (VA, MIT)
• Bruce McKay, BS (MEEI, Cornell)
• Oscar Mendoza (MIT)
• Carmen Scholz, PhD (Alabama)
• Stuart Cogan, PhD (EIC Biomedical)
• William Ellersick, PhD (Analog Circuit Works)
• Sonny Behan (Sonny Behan Consulting)

Medicine and Biology

• Joseph F. Rizzo, MD (VA, MEEI)
• Jinghua Chen, MD, PhD (MEEI)
• Hank Kaplan, MD (Louisville)
• Vasiliki Poulaki, MD (MEEI)
• Shelley Fried, PhD (VA, MGH)
• Ralph Jensen, PhD (VA)
• Ofer Ziv, PhD (VA, MIT)
• Lotfi Merabet, OD, PhD (VA)

Thanks to:

Department of Veterans Affairs, MOSIS, NIH, NSF, DoD, Catalyst Foundation

Discussion