On-chip spatial filter for subretinal implants

Retinal implants are raising hope for blind people to restore part of their visual capabilities. Enormous advances have taken place in this field while several groups worldwide are striving to achieve this long-yearned-for accomplishment. Current studies about visual perception parameters from patients using subretinal implants showed that effects like electric field interference limit the achievable visual acuity. According to our previous work, discussing a model of the implant-plus-retina system, this effect could be moderated by the implementation of a spatial high-pass filter. This work introduces an on-chip realization of a contrast enhancement circuit using a four-neighbor high-pass filter, extending the functionality of an existing retinal stimulator. For the evaluation of different filter kernels a new approach, combining the methods of image processing with the techniques of analog circuit design, is proposed. The circuits discussed in this work are already designed and they will be fabricated in a 180nm CMOS technology in near future.