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Degenerative retinal diseases could cause loss of vision completely. The progress in certain technological fields and multidisciplinary studies conducted with collaboration from different branches of science makes vision restoration possible with visual prosthesis. Visual prosthesis concept uses electrical stimulation of retinal tissue. Computational modeling of retina tissue in silico provides optimization of stimulation parameters and advantages in terms of both financial and time issues. In this study, 3 dimensional retina is modelled and the effects of monophasic electrical stimulation is investigated under stationary conditions. The solution is made using Finite Element Method (FEM). It is concluded that electric field distribution is much more near stimulation electrode than periphery retina. With the needed improvements in the model, it could be used efficiently for time dependent and parameter based investigations. [ABSTRACT FROM AUTHOR]

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The degenerative retina diseases such as Age Related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP) are recently encountered because of visual loss. There is not any known cure for these diseases, but studies are in progress on restoration of visual perception. In studies carried out recently by virtue of innovations in the field of microtechnology, bioengineering, packaging, it is aimed to develop visual prosthesis systems for purposes of activation of visual perception. In this study, various factors affecting efficiency of the visual prosthesis systems are reviewed, and then electric field distribution on tissue is simulated under quasi-static limits by using the finite element analysis. In this context, a layered retina tissue, stimulation and return electrodes which are in contact with the retina tissue are modeled. It is seen that deeper nerve cell communities are stimulated as the potential difference applied between the electrodes increases. Given that the nerve cells need to be stimulated individually for a visual prosthesis system with high resolution, it is concluded that the stimulation electrodes in contact with the tissue need to be penetrated into the tissue. [ABSTRACT FROM PUBLISHER]

In this paper we present a control methodology to smooth the power consumption for battery operated optoelectronic/optogenetic neural prostheses. Optogenetics is a gene therapy method which photosensitizes neurons. It is therefore possible using micro photonics to stimulate neural activity using short high intensity pulses of light. We have previously demonstrated that stimulation can be achieved with combined CMOSGallium Nitride optoelectronic systems. But as these systems have intensity control utilizing pulse width modulation, there is a scaling issue with power supply spikes if large numbers of LEDs are turned on simultaneously. This can lead to power supply inefficiency and intensity droop. We have therefore developed a smoothing methodology, which redistributes pulse width modulation patterns to smooth out power fluctuations. [ABSTRACT FROM PUBLISHER]

The recognition accuracy and response time of Chinese characters formed by simulated irregular phosphene arrays based on changing four parameters —distortion, dropout, pixel-size and grey level were performed. The results of the experiments indicate that the recognition accuracy of different parameters and combinations were increased with the level decreasing from the highest to the lowest level in one day's test. For different days, the trends were increased with the increasing from day 1 to day 15. The response time showed opposite trends. It can be concluded that long-term training would increase the performance of recognition. [ABSTRACT FROM PUBLISHER]