design and analysis of an efficient less noisy biocompatible subretinal cmos imager electrode for visual prosthesis

Abstract

newline The objective of visual prosthesis is to develop techniques which can functionally newlinereplace the degenerated photoreceptors (cells responsible for generating the visual newlinesensations) either by inserting the clinical aid inside the eye or by providing external newlinemeans. Age-related macular degeneration (AMD) and retinitis pigmentosa (RP) were newlinefound to be main cause of vision loss followed by cataract and glaucoma. newlineCategorically visual prosthesis is divided into visual cortex, optic nerve and retinal newlineimplantation techniques for restoration of vision in blinds. With technological newlineadvancements, retinal implants have gained popularity over other methods and newlineadopted as potential way for yielding the artificial vision. Retinal implant is further newlinedivided into two subtypes as epiretinal and subretinal implant. This thesis explores the newlinedesign and analysis of subretinal implant system. The requirement of less stimulation newlinecurrent, less mechanical fixation and reduced surgical trauma are the several newlineadvantages of subretinal implant over epiretinal implant. Subretinal implants are newlinebased on the theory of replacement of degenerated photoreceptors using the newlinemicrophotodiodes, charged coupled devices (CCDs), and nowadays with CMOS newlineimagers. With low-cost, lower power consumption, and integration technology of newlineCMOS devices, nowadays the CMOS imager is the new hope for researchers and newlineclinicians. This work is also based on the utilization of CMOS imager as subretinal newlineimplant device for visual prosthesis. newlineApart from all the advantages of CMOS imager, it still lacks in the noise performance newlinein comparison with other competing devices like CCD. The subretinal implantation newlinestrategy also suffers from the serious drawback of absence of on-chip clock extraction newlinecapability, resulting in dependency on external circuitry causing severe surgical newlineconditions. Further, the placement of subretinal CMOS imager inside the retina newlinegenerates three fundamental concerns. First concern is the dissipation of heat due to newlinethe close proximity of electroni