1. Artificial Retina Imaging For The Sight Impaired: Sensors and Transducers
Robert Jubie
April 14th, 2017

2. Covered in this Presentation:
Anatomy of the Eye
Pathologies of the Eye
How Implants Simulate Vision
Types and locations of Implants
Design and Construction of Implants
Quality of Vision Achieved via Implantation

3. Anatomy of the Eye
Source:

4. Examples of Ocular Pathologies
Glaucoma
Macular Degeneration
Diabetic Retinopathy
Retinal Detachment
Retinitis Pigmentosa

5. Categories of Implants
Epiretinal
Complex Design Requiring External Sensing and Image Processing
Direct Stimulation of Ganglia
Can be used on very damaged retinas
Has FDA Approved Devices
Argus II
Subretinal
Devices in Clinical Trials in US and Approved in Europe
Alpha AMS
Use Photodiode Arrays
Simpler Design
Requires Mostly Intact Retina

6. Location of Implants Johnson Lee J, Scribner Dean A.
Electrode Architecture: Meeting the Challenge of the Retina–Electrode Interface

7. How do Implants Work? Electrical stimulation of cells in the retina
Causes “dots” of light in vision
Activation threshold of cells is inversely proportional to the distance of stimulation
Subretinal implants can remain simple because they use most of the eye’s built in mechanisms for processing imaging
Uses arrays of photodiodes to induce current
Epiretinal implants directly stimulate ganglia and require external sensing such as cameras to obtain visual information
Complex image processing required to create meaningful visual data

8. Construction of Implants
Flexible Designs
Feature Sizes ~ tens of μm
Polyamide over Silicon Substrate Layer
Allows fit to custom curvatures of the retina
Reduces available space for electrodes
Argus II only accommodates arrays of <100 electrodes
Not enough resolution for text or facial recognition
Alpha AMS ~1500 photodiodes
Allows text interpretation
MEMs Based
Micro structured springs that fit to eye curvature
Closer to retinal cells -> Lower excitation current needed
Frail and difficult to implant

9. Construction of Implants
Electrode Architecture: Meeting the Challenge of the Retina–Electrode Interface

10. Construction of Implants
Rigid Designs
Allows for higher densities of electrodes
Arrays of roughly 5000 devices
Large distance between center of implant and retina
Can use silicon columns as micro-leads to penetrate retina
Glass matrix insulation between leads

11. Obtainable Vision with Current Implants
Vision is Pixelated
Degree depends on resolution of electrode array
Large, clear texts can be legible with current experimental technologies
Varying Degrees of Spatial and Temporal Perception
Even low resolution arrays allow navigation through environment
Limited Field of View
Breadth of electrodes determines field of view
Sommerhalder J, Oueghlani E, Bagnoud M, Leonards U, Safran AB, Pelizzone M.
Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning. Vision Res 2003;43:269–283.

12. Going Forward - Conclusions
Retinal Implants have improved over the last several years to where implantees can navigate environments and read text
There are many approaches to retinal implants but the most state of the art use arrays of photodiodes on a flexible polyamide layer and are implanted subretinally
Although resolution has been greatly improved, refresh rates tend to be very slow at < 10 Hz

13. Sources
Sommerhalder J, Oueghlani E, Bagnoud M, Leonards U, Safran AB, Pelizzone M.
Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning. Vision Res 2003;43:269–283.
Johnson Lee J, Scribner Dean A.
Electrode Architecture: Meeting the Challenge of the Retina–Electrode Interface
A 4+1 ARCHITECTURE FOR IN VIVO ELECTROPHYSIOLOGY VISUAL PROSTHESIS
Alejandro Barriga-Rivera1, Calvin D. Eiber1, Paul B. Matteucci1, Spencer C. Chen1, John W. Morley1, 2, 3, Nigel H. Lovell1,
Gregg J. Suaning1
G. Chader; J. Weiland; M. Humayun (2009). "Artificial vision: needs, functioning, and testing of a retinal electronic prosthesis". Progress in Brain Research. 175: 0079–6123. doi: /s (09)
Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS
Katarina Stingl, Karl Ulrich Bartz- Schmidt, Dorothea Besch, Angelika Braun, Anna Bruckmann, Florian Gekeler, Udo Greppmaier, Stephanie Hipp, Gernot Hörtdörfer, Christoph  Kernstock, Assen Koitschev, Akos Kusnyerik, Helmut Sachs, Andreas Schatz, Krunoslav T. Stingl, Tobias Peters, Barbara Wilhelm, Eberhart Zrenner

14. Five Key Concepts
The retina is composed of many cell types and damage to these types determines type of implant that can be used and location
Implants can be either flexible and fitting to the retina, or rigid, each having tradeoffs
Epiretinal implants stimulate ganglia directly – which requires extremely complex designs and external sensing hardware,
Subretinal implants use photodiodes to simulate damaged photoreceptors in the eye – these designs are much simpler and usually consist of implant, ribbon, and wireless power supply
State of the art implants have densities of over 1500 photodiodes per implant, which is enough to allow some patients to see movement, differentiate between light/dark objects, or even read some texts

15. Questions?