Retina implant - a bioMEMS challenge

A key application for microsystems in life-science are active microimplants for restoring and substituting lost or impaired biological functions in humans. The development of functional microdevices that fit in the human eye and that take over lost biological functions to restore vision is a challenge that several international research are engaged in. This paper describes the joint multi-team efforts of German scientists to develop a microelectromechnical implant to stimulate retinal structures for regaining lost visional functions. Different types of active eye implants have been developed for stimulation in the epiretinal and subretinal space. Microelectrode arrays for electrical stimulation have been integrated into flexible and rigid substrates. Innovative microtechniques have been developed for obtaining biocompatible flexible microstructures, interconnects, and hybrid assemblies to fit in the eye ball. Biocompatibility of material and devices was investigated in all design phases utilizing in vitro cell and tissue culture test. Devices at various stages of development have been evaluated in acute and chronic animal models. Passive stimulator electrode arrays (without electronic components) remained in animals for more than 6 months after implantation. Furthermore, animal experiments have shown that active devices equipped with silicon chips could be inserted and housed into the eye. Fully functional chronic devices are presently tested in animals. Experiments on humans are planned in the near future. (C) 2002 Elsevier Science B.V. All rights reserved.