W2 Bionic Eye

Question 1

List the desires vs. challenges that needed to be balanced when considering the development of the Bionic Eye

Answer 1

Desires:

• user expectations
• surgical ease
• small size
• life-long implantable
• fast track to regulatory compliance
• versatility (e.g. channels)
• strong
• flexible
• fast implementation

Challenges:

• human limitations
• multiple iterations
• difficult fabrication
• hermetic challenge
• existing biomaterials with associated limitations
• more features = larger
• stiff materials
• compromises to strength
• $ + collaboration

Question 2

What are the two leading diseases of Retinal Degeneration?

Answer 2

Retinitis pigmentosa (RP) - one of the leading causes of blindness in young people. The leading cause of inherited blindness. Affects 1 in 3500 in USA. ~1.5M affected worldwide.

Age-related macular degeneration (AMD) - a leading cause of blindness in the elderly population. The leading cause of blindness in over 55’s. By 2020, it will affect 3M people in USA.

Question 3

What do the two leading diseases of Retinal Degeneration leave behind which has potential to be harnessed in treatment?

Answer 3

Both RP and AMD leave behind a viable optic nerve

Question 4

What is the location (of the eye) in which a Retinal Prosthesis is located?

Answer 4

Supra-choroidal space.

Substantial thinning of the choroid leads to closer placement of stimulating electrodes to target neurons.

Question 5

What are the layers of the eye from superficial to deep?

Answer 5

Epi-retinal
Nerve fibre layer
Retinal ganglion cells
Amacrine cells
Bipolar cells
Horizontal cells
Photoreceptors
Sub-retinal
Pigment epithelium
Choroid
Supra-choroidal

Question 6

Which cells of the eye die in RP and AMD?

Answer 6

Photoreceptors –> rods and cones.

The cells ‘above’ survive (e.g. horizontal, bipolar, amacrine, retinal ganglion), and can be electrically stimulated

Question 7

When was the original bionic eye patented? What did the first patient report?

Answer 7

Aug. 28, 1956, as a ‘Retinal Stimulator’, a ‘supra-choroidal’ implant.

The patient reported seeing uniform white light in the region of the implant where a “great dark patch” existed prior to the operation. The patient also reported increased confidence in mobility.

Question 8

What are alternative points of intervention in the visual pathway of the nervous system?

Answer 8

Eye –> retina, optic nerve
Lateral Geniculate Nucleus (LGN)
Visual Cortex

Question 9

Describe the implant method of a retinal prosthesis

Answer 9

Array sits within a stable ‘pocket’.
Significantly simplified surgical approach.
Protection of neurons from stimulation by-products due to physical separation (behind choroid).
Can co-exist with residual vision (potential for AMD therapy).

Question 10

What is the general idea for how the bionic eye should work?

Answer 10

Small, supporting electronics affixed to the surface of the globe, inductive power and data supplied from an implant placed behind the ear

Question 11

How does the design of the Electrode Array impact the scleral wound?

Answer 11

Appropriate physical and electrochemical size of electrodes –> minimisation of the scleral wound (currently 3.1 mm)
(appropriate robustness)

Question 12

What are some of the beneficial features of Gregg’s Bionic Eye Microelectronics?

Answer 12

• robust safety features
• parallel stimulation capabilities
• focal activation via hexapolar multiplexing
• threshold reduction through Quasi-monopolar stimulation
• reverse telemetry
• high compliance voltage for stimulation from the suprachoroidal space