IV) Neural Implants to Restore Vision

Question 1

Cite the different types of cell composing the retina in the right order.

Answer 1

Ganglion cell (axon -> cell body), amacrine cells, bipolar cells, horizontal cells and photoreceptor.

Question 2

Site the disease that leads to progressive retinal degeneration and site the stages of progression of the disease.

Answer 2

Retinitis Pigmentosa (RP) - Loss of visual field/tunnel vision/blindness.

Question 3

Which disease causes a loss of vision in the center of the retina ?

Answer 3

Age-Related Macular Degeneration (AMD)

Question 4

Which are the different sites to interface the visual system ?

Answer 4

The retina, the visual cortex and the optic nerve.

Question 5

Which are the different strategies to interface the visual system ?

Answer 5

Using natural information processsing or using human brain to handle technical information.

Question 6

Which other opportunities, appart from treating vision, are available to increase quality of life for blind people ? Specify the limit of each.

Answer 6

Tactile information(poor resolution, not detailed) , auditory representation (interference with normal environment) or etablished aids (stick, dogs).

Question 7

What was the dobelle institute prothetis ?

Answer 7

A cortical vision prosthetis, it consisted in a pair of spetacles with a photoreceptor that was linked to a wire with an array inside the visual cortex. Unfortunately the vision wasn’t fully restored and the device elicited some epileptic seizure.

Question 8

Site two other cortical vision prosthetis trials after the dobelle institute one (MEMS approcaches)

Answer 8

Pritzker insitute (1024 IC electrodes).
Cortivis (128 IC electrodes)

Question 9

Describe the principle of the optic nerve prosthetis by prof c.Verrart and colleges.

Answer 9

Artificial eye on a google linkked to an external processor itself linked to coils linked to neurostimulator. The neurostimulator send charges to a sporal cuff electrode that stimulate the spiral cuff electrode. It has been tested on two patientsextraduraly (via orbiter with 8 polar cuff electrode), or intradurally (via temporal lobe with 4 polar cuff electrode)

Question 10

Site five system requirement for a retina implant.

Answer 10

Implantable in the eye (weight, dimension, visual inspection of the retina), energu supply (no battery, wireless), telemetric data transmission from camera or encoder, biocompatibility, long term stability.

Question 11

What are the two types of implants for a retina implant ?

Answer 11

Epiretinal (on the ganglion cell)
Subretinal (between bipolar cells and piment epithelium) this is a technical signal encoding. The stimulation, in this case, is made via graded potential.
-with photo diodes, no subthreshold

Question 12

What was the aim of the microphotodiode array ?

Answer 12

The MPDA is a device with cells that react to light, the back side of the counter electrode stimulate the retina.

Question 13

Which problems were related to the Microphotodiode array ?

Answer 13

The resolution was poor so they had to increase the side of the array.
When they applied it in vivo but they were not made for wet environment.

Question 14

What was the problem with the subretinal vision prosthesis ?

Answer 14

The light was not enough to stimulate the device so they added a powerpump, then this was remplaced by a telemetric device.

Question 15

Site the main component of an epiretinal vision prothesis.

Answer 15

CMOS camera in glasses, retina encoder in handled PC, data transmission and energy supply in glasses and an implant.

Question 16

What is the limit of a retina encoder ?

Answer 16

The different cells composing the retina communicate toether via transfer function but we don’t know exacty how this work, we should in order to mimic them as close a possible.

Question 17

Site systems requirements for retina implant .

Answer 17

The implantability into the eye (size, weight, visual inspection of retina); the energy supply (wireless, no battery), wireless signal transmission from camera/encoder, biological compatibility and long term stability.

Question 18

Site the elements on the scheme of the epiretinal vision implant concepts.

Answer 18

(Telemetry transmitter, single chip CMOS camera, poer data, signal processor, telemetry receiver, micro cable, encapsulated retina stimulator, microelectrodes array, stimulation electronic).

Question 19

Which material is the best for flexible substrate and why ?

Answer 19

Polyimide (PI 2611), thin and flexible, lightweight and low water absorbtion.

Question 20

Define the method for process technology to create flexible subtrates with integrated electrodes and tracks and on the scheme, define the composants.

Answer 20

‘sandwich method”, Gold (interconnects), Platinum (electrodes), polyimide.

Question 21

What are the requirements for the electrodes in a retina ?

Answer 21

Implantability, technical stability, the adaptation to the eyeball, and the physiological requiements.

Question 22

Where to check up for toxicity of materials ?

Answer 22

ISO 10993: biological evaluation of medical devices.

Question 23

Site the different methods of assembly technologies for retinal implant.

Answer 23

The “retina tack” (harpoon), glueing (long term stability -), soldering (toxic, corrosive), Bondig (with wire, MFI, fliip chip) or monolothic integration.

Question 24

What is the Microflex interconnection ?

Answer 24

A standard technology for neural implant based on the modification of ball wedge bonding technique it is used for the riveting of subtrates to flexible ribbon cables.

Question 25

Define the different part of a retinal implant.

Answer 25

receiver part with diode, capacitor, coil an receiver chip.

Stimulator part with the stimulator chip and the stimulation electrodes.

Question 26

Which type of electrodes have been used for the retina imlant ?

Answer 26

Bull eyes electrode with two metal layers?

Question 27

What is the material for encapsulation of retinal implant ?

Answer 27

Parylene C.

Question 28

CIte the steps for implantation of an epiretinal vision prothesis.

Answer 28

1 vitrectomy, kryopexy, 2 phakoemulsification, perfluocarbon 3 § stimulator implantation, 4 receiver implantation, 5 fixation.

Question 29

Why did they try acute stimuation of the retina to test the material ?

Answer 29

to check if retina stimulation elicited electrical activity of the optic nerve.