Forward scattered light from the anterior segment of the human eye can be measured by Shack-Hartmann (SH) wavefront aberrometers with limited visual angle. We propose a novel Point Spread Function (PSF) reconstruction algorithm based on SH measurements with a novel measurement devise to overcome these limitations.In our optical setup, we use a Digital Mirror Device as variable field stop, which is conventionally a pinhole suppressing scatter and reflections. Images with 21 different stop diameters were captured and from each image the average subaperture image intensity and the average intensity of the pupil were computed. The 21 intensities represent integral values of the PSF which is consequently reconstructed by derivation with respect to the visual angle. A generalized form of the Stiles-Holladay-approximation is fitted to the PSF resulting in a stray light parameter Log(IS). Additionaly the transmission loss of eye is computed. For the proof of principle, a study on 13 healthy young volunteers was carried out. Scatter filters were positioned in front of the volunteer's eye during C-Quant and scatter measurements to generate straylight emulating scatter in the lens. The straylight parameter is compared to the C-Quant measurement parameter Log(ISC) and scatter density of the filters SDF with a partial correlation.Log(IS) shows significant correlation with the SDF and Log(ISC). The correlation is more prominent between Log(IS) combined with the transmission loss and the SDF and Log(ISC).Our novel measurement and reconstruction technique allow for objective stray light analysis of visual angles up to 4 degrees.

Objective measurement of straylight in the human eye with a Shack–Hartmann (SH) wavefront aberrometer is limited in imaging angle. We propose a measurement principle and a point spread function (PSF) reconstruction algorithm to overcome this limitation. In our optical setup, a variable stop replaces the stop conventionally used to suppress reflections and scatter in SH aberrometers. We record images with 21 diameters of the stop. From each SH image, the average intensity of the pupil is computed and normalized. The intensities represent integral values of the PSF. We reconstruct the PSF, which is the derivative of the intensities with respect to the visual angle. A modified Stiles Holladay approximation is fitted to the reconstructed PSF, resulting in a straylight parameter. A proof-of-principle study was carried out on eight healthy young volunteers. Scatter filters were positioned in front of the volunteers’ eyes to simulate straylight. The straylight parameter was compared to the C-Quant measurements and the filter values. The PSF parameter shows strong correlation with the density of the filters and a linear relation to the C-Quant straylight parameter. Our measurement and reconstruction techniques allow for objective straylight analysis of visual angles up to 4 deg.

Ensuring medical support of patients of advanced age in rural areas is a major challenge. Moreover, the number of registered doctors—medical specialists in particular—will decrease in such areas over the next years. These unmet medical needs in combination with communication deficiencies among different types of health-care professionals pose threats to the quality of patient treatment. This work presents a novel solution combining telemedicine, telecooperation, and IHE profiles to tackle these challenges. We present a telecooperation platform that supports longitudinal electronic patient records and allows for intersectoral cooperation based on shared electronic medication charts and other documents. Furthermore, the conceived platform allows for an integration into the planned German telematics infrastructure.

To examine the use of a modified Hartmann–Shack wave front aberrometer (WASCA; Carl Zeiss Meditec AG, Germany) to measure objective stray light caused by forward light scatter from the anterior segment of the human eye.

Article MODERNE INFORMATIONSTECHNOLOGISCHE WERKZEUGE BEI DER REALISIERUNG VON MEDIZINISCHEN LEITLINIEN-SERVERN was published on January 1, 2000 in the journal Biomedical Engineering / Biomedizinische Technik (volume 45, issue s1).

To avoid the problem of knowledge acquisition bottleneck a process oriented method for knowledge acquisition was developed. The approach is based on so called scenarios. A scenario describes a certain step within the decision process to be elicited from the medical expert. By using scenario techniques the knowledge engineer is able to represent the elicited knowledge in a way that give both experts control over the whole acquisition process. Key-Words: Knowledge Acquisition, Process, Model, Medicine

EINFÜHRUNG Informationssysteme in der klinischen Routine sind häufig heterogen, inkompatibel und redundant. Damit sind Probleme bei der Verwaltung und Speicherung von Daten sowie dem Einsatz unterschiedlicher Applikationen vorgezeichnet. Im Rahmen eines gemeinsamen Forschungsprojektes mit der Klinik für Intensivmedizin und Anästhesiologie wird bei Einsatz moderner Methoden des Software-Engineering ein experimentelles Stations-Informations-System SIS entwickelt. Dabei ergeben sich eine Reihe von Anforderungen, die man im Sinne einer Wunschliste wie folgt aufführen kann.

Im klinischen Bereich und in der Forschung wird für die Analyse von mehrkanaligen bioelektrischen Signalen eine Vielzahl unterschiedlichster Dateiformate verwendet. Sie sind häufig hardware-spezifisch oder für ganz spezielle Anwendungen entwickelt. Die Aufzeichnung bioelektrischer Signale gestaltet sich durch eine Reihe von Zusatzinformationen u.U. sehr komplex. Dadurch bedingt ist immer wieder ein großer Zeitaufwand für die programmtechnische Umsetzung simpler Aufgaben (z.B. Leseund Schreibroutinen). Ebenso inakzeptabel ist es, daß uneinheitliche Datenformate wieder und wieder Neuimplementierungen von Standardroutinen der Signalverarbeitung erzwingen.

A central problem for the design of knowledge-based systems is the so-called knowledge acquisition bottleneck. Knowledge acquisition is crucial for the quality and efficiency of a planned knowledge-based system. These systems are always based on one or several knowledge bases, whose contents are an influential quality factor for the system's result. For that reason, it is evident that a consistent approach to knowledge acquisition is of great importance. In relation to the problem domain the knowledge-based system is intended for, the knowledge acquisition can be highly problematic. While, for example, in technical problem domains, the access to expert knowledge can usually be achieved in an acceptable manner, the acquisition of medical knowledge for formalisation and usage in an information system is not possible without difficulty

Medical guidelines provide algorithms to optimize intensive care and reduce the costs of therapy. Therefore, guideline servers provide topical medical knowledge and research results for a wide range of users without any delay of time. The knowledge is not only visualized. Knowledge based information systems are used for guidance and to optimize the goals of the medical therapy process. These information systems may supported by semantic agents for information retrieval. This results in a contribution for quality assurance in medicine by information systems. Key-Words: Agents, Medical Information System, Medical Guideline Server, Knowledge Acquisition