Abstract

P 234

A demonstrator device for illustration of the main functions of an Artificial Accommodation System

Helmut Guth, Ulrich Gengenbach, Andreas Hellmann, Rudolf Scharnowell, Klaus Peter Scherer, Ingo Sieber, Peter Stiller
Institut für Angewandte Informatik, Forschungszentrum Karlsruhe GmbH, Eggenstein-Leopoldshafen

Objective
In an aging society presbyopia and cataract are issues of increasing importance. Hence an intelligent, autonomous microsystem that can be implanted in place of an IOL in cataract surgery is being developed. In order to illustrate the main functions of such a system an upscaled demonstrator device has been built. The subsystems whose interaction shall be demonstrated are sensor system for accommodation demand measurement and optics with adjustable refraction power.
Methods
The demonstrator consists of two eyeballs on the scale of 5:1 with respect to their natural archetype. They are composed of a cornea lens, the CCD-chip of a video camera as retina equivalent and in between, behind an aperture the optics with adjustable refractive power (active optics). These eyeballs are set up in such a way that they automatically follow an object that is being moved in the plane in front of them. For control purposes the images acquired by the CCD-camera are displayed live on a monitor. Moreover the eyeballs house sensors to measure accommodation demand. Control of the active optics based on these sensor signals and is being done on a PC.
Results
In this demonstrator the accommodation demand is determined by measuring the angular position of the eyeballs with respect to the earth’s magnetic field. This information allows calculation of the vergence angle which in turn yields the accommodation demand. An Alvarez-Humphrey lens as active optics and a downstream aspherical lens provide the required refraction power to ensure acute imaging of the sighted target on the CCD-chip. A piezo motor is used for adjustment of the Alvarez-Humphrey lens by lateral motion of the two lens components.
Conclusions
The demonstrator illustrates nicely how two main subsystems of an Artificial Accommodation System, the sensor system for accommodation demand measurement and optics with adjustable refraction power interact. The device is of modular design; thus its components can be changed for evaluation of other active principles.

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