1. EPI-RET: IIP Animal experiment
1mC/cm2 is a reasonable safety level to avoid retinal edema
Acute human experiments in 20 RP patients
phosphene (+): 19 patients
threshold (+): 15 patients
perception threshold: 191.5±189.7nC (20-380)
Size: match head (36%), coin (35%), apple (23%) in 1m distance, previewed experiment
brightness: candle (45%), light bulb (33%)
color: white (31%), yellow (30%), blue (22%)

2. Epiretinal IIP technologie, Hamburg-Eppendorf

4. Fixation of retinal stimulator
glue
biochemically unstable; species difference
degeneration of inner retina (rabbit)
fibrin formation (pig)
metal retinal tack
invasive to membrane & tissues, expensive
material: titanium
silicon retinal tack
photolithography; mass produce, reproduce
easily shaped

5. Stimulating Electrode
Suprachoroidal NIDEK-Osaka University
Vitreous
Stimulating Electrode
Reference electrode

6. Optic Nerve Stimulator
Pros.
For severe retinal damage
Cons.
High density of axons (1.2million/2mm diameter) with tough dura
Specialized topological arrangement of nerve fibers
UCL (Universite Catholique de Louvain), Belgium
Stimulation level: BC  GC  ON  LGN  VC
1998. First human trial in the blind patient due to glaucoma
2004. Second human trial
spiral cuff electrode (Au-Ti)

7. Optic Nerve Stimulator
good retinotopic correspondence but poor spatial resolution
phosphene location depended on gaze direction
phosphene size and position are very different from what could have been expected on the basis of the the retinotopically activated axons in the optic nerve

11. 50° field
10° / Div

12. Visual Cortex Stimulator
Pros.
Therapeutic potential is greatest - more wide range of indication, e.g. optic nerve damage
Cons.
Neurosurgery: It’s no kidding!!
Difficulty of maintaining a stable interface
More complex topology of neurons
Epileptogenic property: occipital lobe epilepsy ?
Utah, Dobelle Inst., Kresge
Stimulation level: BC  GC  ON  LGN  VC

13. Visual Cortex Stimulator
Dobelle & Mladejovsky (1974)
'acute' 38 experiments, succeeded in 15 patients undergoing brain surgery, using 11 Pt electrode
area no. 17 seems the most effective locus for cortical stimulation
Dobelle (1974)
'Artificial Vision for the Blind' in Science
64 Pt electrode, 8 x 8 array on 3 mm centers in Teflon ribbon cable matrix
pattern recognition was unsuccessful

14. Visual Cortex Stimulator
Dobelle (1976):
“'Braille' reading by a blind volunteer by visual cortex stimulation” in Nature
64 Pt electrode, 8 x 8 array on 3 mm centers in Teflon ribbon cable matrix
6 non-interacting phosphenes were selected to form a ‘braille cell’

15. Visual Cortex Stimulator
Normann
MEMS hairbrush depth probe
Si-array, multi-point stimuli
1.5mm below the surface of the visual cortex
RF telemetry
intracortical vs. surface stimuli
Thresholds : x2 to x3 lower
2-point resolution: x5 closer
Small phosphenes
Electronic components must be small and resilient
Techniques for surgical implantation and recording
High insertion speed
Avoid tissue injury, inflammation, tissue destruction
Topographic relationship
poor correlation between stimulating pattern and recognition pattern

16. Telemetry Simple daylight; Optobionics Wired; Dobelle
RF; Doheny-NCSU, Louvain
Laser; MEEI-MIT

17. Chemical stimulation Pros. Cons. “Caged glutamate” Releasing
no electric current
no heat
no oxidation
high specificity to soma
high spatial resolution
high turnover
Cons.
transscleral device
need reservoir
pharmacokinetics
glutamate excitotoxicity
in vivo microfluidic device
“Caged glutamate”
C60 buckminsterfullerene
glutamate conjugate
Releasing
EXCIMER
Ga:N UV LED
Stanford, Wayne State Univ.

18. Image still image vs. moving image - “motion blur”
steady image vs. flickering image - “flicker fusion”
Essential functions; eye positioning, data compression, contrast enhancement, image remapping & customization
How many pixels are required ?
25 x 25 : 20/440 - independent movement
32 x 32 : 20/26 - character recognition with LVA
8bit 8bit 4bit bit
320x x32 32x x8

19. Mapping nonlinearity

20. SNU Prosthesis Chip I Front Chip II Back Data/Power Receiver Chip
Current Stimulator Chip
In the year 2004, we showed that….
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