Abstract
To treat retinal degenerative diseases, a transcorneal electrical stimulation-based system is proposed, which consists of an eye implant and an external component. The eye implant is wirelessly powered and controlled by the external component to generate the required bi-polar current pattern for transcorneal stimulation with an amplitude range of 5 μA to 320 μA, a frequency range of 10 Hz to 160 Hz and a duty ratio range of 2.5% to 20%. Power delivery control includes power boosting in preparation for stimulation, and normal power regulation that adapts to both coupling and load variations. Only one pair of coils is used for both the power link and the bi-directional data link. Except for the secondary coil, the eye implant is fully integrated on chip and is fabricated using UMC (United Microelectronics Corporation, Hsinchu, Taiwan) 0.13 μm complementary metal-oxide-semiconductor (CMOS) process with a size of 1.5 mm × 1.5 mm. The secondary coil is fabricated on a printed circuit board (PCB) with a diameter of only 4.4 mm. After coating with biocompatible silicone, the whole implant has dimensions of 6 mm in diameter with a thickness of less than 1 mm. The whole device can be put onto the sclera and beneath the eye’s conjunctiva. System functionality and electrical performance are demonstrated with measurement results.
Highlights
Retinal degenerative (RD) diseases are a clinically and genetically heterogeneous group of primary retinal abnormalities that cause degeneration of the photoreceptors or the retinal pigment epithelium and lead to progressive loss of vision
Transcorneal electrical stimulation (TcES) is one of the therapies that promotes the survival of photoreceptors and preserves retinal functions [1]
The internal implant unit consists of the power supply module, the data telemetry module, the digital controller and the stimulation unit
Summary
Retinal degenerative (RD) diseases are a clinically and genetically heterogeneous group of primary retinal abnormalities that cause degeneration of the photoreceptors (rods and cones) or the retinal pigment epithelium and lead to progressive loss of vision. It consists of an external control unit and an internal. The internal implant unit consists of the power supply module, the data telemetry module, the digital controller and the stimulation unit. A detection coil is used to receive the back-scattered data transmitted from the internal implant unit, and a digital controller is used to encode and decode the data For this TcES system, the power link and the data link share the same pair of coils. Power boosting is activated to increase the transmission power prior to the scheduled task of electrical stimulation With these proposed power control strategies, the rectified DC output is well regulated and achieves better immunity to coupling and loading variations. The current amplitude can be programmed to range from 5 μA to 320 μA, the stimulation frequency from 10 Hz to 160 Hz, and the current pulse duty ratio from 2.5% to 20%
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