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Thomas Martin, Ulrich Gengenbach, Helmut Guth, Georg Bretthauer, Rudolf F. Guthoff; Actuator concepts for the optics of an Artificial Accommodation System. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1369.
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An implantable mechatronic microsystem is a novel approach to restore the accommodation ability after catarct surgery or in case of presbyopia. It consists of a sensor to detect the accommodation demand, optics of variable refractive power, a microcontroller, energy supply, a communication device and a biocompatible and hermetic encapsulation. Axial-shift optics as well as lateral-shift optics have been shown to be suitable for such an implant. They have to be driven by an actuator. The paper presents an approach to this challenge as well as two elaborated actuator solutions.
Quasistatically driven piezoelectric actuators offer high dynamics, energy efficiency, reliability, and durability proven on an industrial level. For the required axial or lateral lens shifts of about 300 µm mechanical displacement amplification is necessary. It can be accomplished by a planar compliant mechanism linkage in wear-free single-crystal silicon that also realizes suspension and synchronization of the lenses. Different designs have been elaborated and verified by finite element analysis (FEA) of the linkages. Linkages for the axial-shift optics have been fabricated on a scale of 1.5:1 and characterized by measurements.
Compact actuator solutions with novel compliant mechanisms for axial-shift optics as well as lateral-shift optics have been elaborated (Fig. 1). They are virtually friction-free, designed for high durability, and feature postoperative refractive compensation. A safe failure state is ensured the implant being equivalent to a conventional IOL. Fabricated linkages were measured to have an unloaded displacement amplification ratio of 18.1 (SD = 0.80, n = 5) which is in excellent agreement with the ratio of 18.1 calculated by FEA indicating sufficient displacement amplification to generate the required lens shift.
Actuator solutions were presented that meet the requirements for an Artificial Accommodation System - bringing the implant closer to realization.
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