This document describes a photovoltaic retinal prosthesis being developed to restore sight to blind patients suffering from retinal diseases. The prosthesis uses a video camera and LCD display to project near-infrared images onto a subretinally implanted chip containing photovoltaic pixels. Pillar microstructures on the chip prompt the retina to migrate close to the implant, allowing the pixels to electrically stimulate remaining retinal neurons and produce perceptions of light. Previous implants with fewer electrodes showed promising results, but a prosthesis with thousands of pixels may be needed to provide functional vision like reading or face recognition.

1. Photovoltaic Retinal
Prosthesis for Restoring Sight to the Blind
Presented by
Roopa.D Vyshnavi.K
10JM1A0528 10JM1A0529
CSE, 3rd year CSE, 3rd year

2. PHOTOVOLTAIC RETINAL
PROSTHESIS FOR RESTORING
SIGHT TO THE BLIND

3. ABSTRACT:
Blindness is one of the most devastating consequences of disease. We develop electronic retinal
prosthesis for restoration of sight to patients suffering from degenerative retinal diseases such as
Retinitis Pigmentosa and Age-Related Macular Degeneration.
In these conditions the photoreceptor cells slowly degenerate, leading to blindness. However,
many of the inner retinal neurons that transmit signals from the photoreceptors to the brain are
preserved to a large extent for a prolonged period of time.
Electrical stimulation of the remaining retinal neurons can produce phosphenes - perception of
light, and the first retinal implants involving a small number of electrodes (16 to 60) yielded
encouraging results in patients with retinal degeneration. However, thousands of pixels are likely
to be required for functional restoration of sight, such as reading and face recognition.

4. Contents
 SYSTEM DESIGN
 PROXIMITY OF ELECTRODES TO TARGET CELLS

5. SYSTEM DESIGN
Data stream from a video camera is
processed by a pocket PC, and the
resulting images are displayed on a liquid
crystal micro display (LCD), similar to video
goggles. The LCD corresponding to
approximately 30 degrees of visual field is
illuminated with a pulsed (1 ms) near-
infrared (~900 nm) light, projecting the
images through the eye optics onto the
retina. The IR image is then received by
the photovoltaic pixels in a subretinally
implanted chip.

6. SYSTEM DESIGN
Optical approach to information delivery
allows for simultaneous activation of
thousands of pixels in the implant, and
retains a natural link between the eye
movements and the visual perception.
Since each photovoltaic pixel operates
independently, they do not need to be
physically connected to each other. Thus,
segments of the array may be separately
placed into the subretinal space, greatly
simplifying surgery.

7. PROXIMITY OF ELECTRODES TO TARGET CELLS
Addressing the problem of proximity, we
have found that certain 3-dimensional
microstructures prompt the retina to
migrate into very close proximity to the
implant with its neural circuitry largely
intact. One strategy involves pillar
microelectrodes that, upon retinal
migration, reach the required layer of cells.

8. Histology of the RCS rat retina 6
weeks after implantation of a pillar
array into a subretinal space. Tops
of the pillars achieve an intimate
proximity with the cells in the inner
nuclear layer.
Conceptual diagram of the photovoltaic
pixels with pillar electrodes (1)
penetrating into the inner nuclear layer.
The return electrodes (2) are located in
the plane of the photodiodes.

9. CONCLUSION
Blindness is one of the most devastating consequences of disease. We develop electronic retinal
prosthesis for restoration of sight to patients suffering from degenerative retinal diseases such as
Retinitis Pigmentosa and Age-Related Macular Degeneration. In these conditions the
photoreceptor cells slowly degenerate, leading to blindness. However, many of the inner retinal
neurons that transmit signals from the photoreceptors to the brain are preserved to a large extent
for a prolonged period of time.
Electrical stimulation of the remaining retinal neurons can produce phosphenes - perception of
light, and the first retinal implants involving a small number of electrodes (16 to 60) yielded
encouraging results in patients with retinal degeneration. However, thousands of pixels are likely
to be required for functional restoration of sight, such as reading and face recognition.