Walter Wrobel

Restoration of useful vision up to letter recognition capabilities using subretinal microphotodiodes

Our group has developed a subretinal microphotodiode array for restoration of vision. In a clinical pilot study the array has been implanted in 11 patients suffering from photoreceptor degenerations. Here we present promising results from some of those patients where the retinal tissue above the chip was functional and the implant fulfilled its expected function. A spatial resolution of approximately 0.3 cycles/degree could be achieved with fine stripe patterns. In one subject where the implant had been placed directly under the macular region of the retina a visual acuity of 20/1000 could be measured. Artificially restored visual acuity of this quality has not been reported previously. Finally, we present images illustrating an approximation of how the visual perceptions might have appeared to the subjects, based on a mathematical model and patient reports.

Laboratory and clinical reliability of conformally coated subretinal implants

Despite recent developments and new treatments in ophthalmology there is nothing available to cure retinal degenerations like Retinitis Pigmentosa (RP) yet. One of the most advanced approaches to treat people that have gone blind due to RP is to replace the function of the degenerated photoreceptors by a microelectronic neuroprosthetic device. Basically, this subretinal active implant transforms the incoming light into electric pulses to stimulate the remaining cells of the retina. The functional time of such devices is a crucial aspect. In this paper the laboratory and clinical reliability of the two active subretinal implants Alpha IMS and Alpha AMS is presented. Based on clinical data the median operating life of the Alpha AMS is estimated to be 3.3 years with a one-sided lower 75 % confidence level of 2.0 years. This data shows a significant improvement of the device lifetime compared to the previous device Alpha IMS which shows a median lifetime of 0.6 years with a lower confidence bound (75 %) of 0.5 years. The results are in good agreement with laboratory data from accelerated aging tests of the implant components, showing an estimated median lifetime for Alpha IMS components of 0.7 years compared to the improved lifetime of Alpha AMS of 4.7 years.