Photovoltaic Retinal Prosthesis for Restoring Sight to the Blind

Presented byRoopa.D Vyshnavi.K

10JM1A0528 10JM1A0529CSE, 3rd year CSE, 3rd year

PHOTOVOLTAIC RETINAL PROSTHESIS FOR RESTORING

SIGHT TO THE BLIND

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.

Contents

SYSTEM DESIGN

PROXIMITY OF ELECTRODES TO TARGET CELLS

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.

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.

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.

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.

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.