A 1600-pixel Subretinal Chip with DC-free Terminals and ±2V Supply Optimized for Long Lifetime and High Stimulation Efficiency

Retinal implants are developed to restore visual perception in blind patients. The retina can be stimulated from either side (epiretinal (M. Ortmanns et al., 2007) or subretinal (L. Theogarajan et al., 2006), (E. Zrenner, 2002)). With a subretinal light sensitive chip, the natural optical system of the eye is still used, allowing the patient to intuitively locate objects. The patient was 1 out of 7, who have been implanted in a clinical study in 2006 in Tuebingen, Germany (E. Zrenner et al., 2007). The space beneath the retina is limited. Either just an electrode array is placed there (L. Theogarajan et al., 2006), or a silicon chip thinned to about 70mum, or both. The experiments (E. Zrenner et al., 2007) used a device including a light-sensitive CMOS chip and separate direct stimulation electrodes. The device was connected to an external power supply by a polyimide-ribbon (comparable to (L. Theogarajan et al., 2006), however much longer), forming a flexible connection into the eyeball. Feasibility of the wired supply approach for humans was proven; no perception of the ribbon was reported by the patients. After 5 weeks, all implants were removed, and no damage of the patient's retina was observed.