Microphotodiode array

Photodiode arrays have been used as retinal implants [684]. These arrays of p-i-n diodes are fabricated on a thin titanium layer bonded to a glass plate. The total thickness of this flexible structure is 1.5 yum. The microphotodiode array (MPDA) is used to replace photoreceptors (rods and cones) that have become defective due to disease. 

Alan Chow from Optobionics spoke about his Artificial Silicon Retina (ASR) [14], ASRs are semiconductor-based silicon chip microphotodiode arrays (microscopic solar cells) designed to be surgically implanted into the subretinal space. The arrays are approximately 2 to 3 mm in diameter, 50 to 75 /um thick. Dr. Chow reported successful electrical stimulation of normal animal retinas. 

Chow, A.Y. and Peachey, N.S. The subretinal microphotodiode array retinal prosthesis. Ophthalmic Res. 30 195-198,1998. 

Hammerle H, Kobuch K, Kohler K, Nisch W, Sachs H, SteMe M (2002) BiostabiUty of microphotodiode arrays for subretinal implantation. Biomaterials 23 797. 

Chow AY, Paidue MT, Chow VY, Peyman GA, Liang C, Perlman JI, Peachey NS (2001) Implantation of silicon chip microphotodiode arrays into the cat subretinal space. Neural Systems and Rehabilitation Engineering, IEEE Transactions on 9(l) 86-95, E)OI 10.1109/ 7333.918281... 

Systems have been tested in blind humans in several clinical trials. For brevity, the two main trials that have produced the most significant results will be discussed. Retina Implant, GmbH has developed an externally powered, subretinal microphotodiode array (Figure 3-top). This device has been tested in 12 subjects (Zrenner et al., 2011). The device has 1,500 repeating units on a single silicon chip. Each unit has the following elements a microphotodiode to sense light. 

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