253 research outputs found
Microcomputer-based artificial vision support system for real-time image processing for camera-driven visual prostheses
It is difficult to predict exactly what blind subjects with
camera-driven visual prostheses (e.g., retinal implants) can perceive.
Thus, it is prudent to offer them a wide variety of image processing
filters and the capability to engage these filters repeatedly in any userdefined
order to enhance their visual perception. To attain true portability,
we employ a commercial off-the-shelf battery-powered general
purpose Linux microprocessor platform to create the
microcomputer-based artificial vision support system (µAVS^2) for
real-time image processing. Truly standalone, µAVS^2 is smaller than a
deck of playing cards, lightweight, fast, and equipped with USB, RS-
232 and Ethernet interfaces. Image processing filters on µAVS^2 operate
in a user-defined linear sequential-loop fashion, resulting in vastly
reduced memory and CPU requirements during execution. µAVS^2
imports raw video frames from a USB or IP camera, performs image
processing, and issues the processed data over an outbound Internet
TCP/IP or RS-232 connection to the visual prosthesis system. Hence,
µAVS^2 affords users of current and future visual prostheses independent
mobility and the capability to customize the visual perception
generated. Additionally, µAVS^2 can easily be reconfigured for other
prosthetic systems. Testing of µAVS^2 with actual retinal implant carriers
is envisioned in the near future
Wafer-Level Parylene Packaging With Integrated RF Electronics for Wireless Retinal Prostheses
This paper presents an embedded chip integration
technology that incorporates silicon housings and flexible
Parylene-based microelectromechanical systems (MEMS) devices.
Accelerated-lifetime soak testing is performed in saline at elevated
temperatures to study the packaging performance of Parylene C
thin films. Experimental results show that the silicon chip under
test is well protected by Parylene, and the lifetime of Parylenecoated
metal at body temperature (37°C) is more than 60 years,
indicating that Parylene C is an excellent structural and packaging
material for biomedical applications. To demonstrate the proposed
packaging technology, a flexible MEMS radio-frequency (RF) coil
has been integrated with an RF identification (RFID) circuit die.
The coil has an inductance of 16 μH with two layers of metal
completely encapsulated in Parylene C, which is microfabricated
using a Parylene–metal–Parylene thin-film technology. The chip
is a commercially available read-only RFID chip with a typical
operating frequency of 125 kHz. The functionality of the embedded
chip has been tested using an RFID reader module in both air
and saline, demonstrating successful power and data transmission
through the MEMS coil
Lycium barbarum Polysaccharide Improves Bipolar Pulse Current-Induced Microglia Cell Injury Through Modulating Autophagy
published_or_final_versio
Wide field epiretinal micro-electrode-design and feature test
This study was aimed to design and fabricate a wide field implantable epi-retinal microelectrode array for the purpose of retinal repair, and to perform electrochemical test on the array. With parylene as flexible substrate material and Pt as electrode and route material, microelectrode array prototypes was designed and fabricated, and electric characteristics of the array was tested with the three-electrode test system. The feature analysis showed that morphological and electrical properties of the array well met the requirements of implantation and electrical stimulation of retina. The microelectrode array can be put in the in vivo electrophysiological experiments on animal and can perform reliably. © 2013 IEEE.published_or_final_versio
Implantable CMOS Biomedical Devices
The results of recent research on our implantable CMOS biomedical devices are reviewed. Topics include retinal prosthesis devices and deep-brain implantation devices for small animals. Fundamental device structures and characteristics as well as in vivo experiments are presented
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Visual Acuity of Simulated Thalamic Visual Prostheses in Normally Sighted Humans
Simulation in normally sighted individuals is a crucial tool to evaluate the performance of potential visual prosthesis designs prior to human implantation of a device. Here, we investigated the effects of electrode count on visual acuity, learning rate and response time in 16 normally sighted subjects using a simulated thalamic visual prosthesis, providing the first performance reports for thalamic designs. A new letter recognition paradigm using a multiple-optotype two-alternative forced choice task was adapted from the Snellen eye chart, and specifically devised to be readily communicated to both human and non-human primate subjects. Validation of the method against a standard Snellen acuity test in 21 human subjects showed no significant differences between the two tests. The novel task was then used to address three questions about simulations of the center-weighted phosphene patterns typical of thalamic designs: What are the expected Snellen acuities for devices with varying numbers of contacts, do subjects display rapid adaptation to the new visual modality, and can response time in the task provide clues to the mechanisms of perception in low-resolution artificial vision? Population performance (hit rate) was significantly above chance when viewing Snellen 20/200 optotypes (Log MAR 1.0) with 370 phosphenes in the central 10 degrees of vision, ranging to Snellen 20/800 (Log MAR 1.6) with 25 central phosphenes. Furthermore, subjects demonstrated learning within the 1–2 hours of task experience indicating the potential for an effective rehabilitation and possibly better visual performance after a longer period of training. Response time differences suggest that direct letter perception occurred when hit rate was above 75%, whereas a slower strategy like feature-based pattern matching was used in conditions of lower relative resolution. As pattern matching can substantially boost effective acuity, these results suggest post-implant therapy should specifically address feature detection skills
Data analysis of retinal recordings from multi-electrode arrays under in situ electrical stimulation
The development of retinal implants has become an important field of study in recent years, with increasing numbers of people falling victim to legal or physical blindness as a result of retinal damage. Important weaknesses in current retinal implants include a lack of the resolution necessary to give a patient a viable level of visual acuity, question marks over the amount of power and energy required to deliver adequate stimulation, and the removal of eye movements from the analysis of the visual scene. This thesis documents investigations by the author into a new CMOS stimulation and imaging chip with the potential to overcome these difficulties. An overview is given of the testing and characterisation of the componments incorporated in the device to mimic the normal functioning of the human retina. Its application to in situ experimental studies of frog retina is also described, as well as how the data gathered from these experiments enables the optimisation of the geometry of the electrode array through which the device will interface with the retina. Such optimisation is important as the deposit of excess electrical charge and energy can lead to detrimental medical side effects. Avoidance of such side effects is crucial to the realisation of the next generation of retinal implants
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