Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a new technique to detect changes in the human retina. The autofluorescence decay over time, generated by endogenous fluorophores, is measured in vivo. The strong autofluorescence of the crystalline lens, however, superimposes the intensity decay of the retina fluorescence, as the confocal principle is not able to suppress it sufficiently. Thus, the crystalline lens autofluorescence causes artifacts in the retinal fluorescence lifetimes determined from the intensity decays. Here, we present a new technique to suppress the autofluorescence of the crystalline lens by introducing an annular stop into the detection light path, which we call Schweitzer's principle. The efficacy of annular stops with an outer diameter of 7 mm and inner diameters of 1 to 5 mm are analyzed in an experimental setup using a model eye based on fluorescent dyes. Compared to the confocal principle, Schweitzer's principle with an inner diameter of 3 mm is able to reduce the simulated crystalline lens fluorescence to 4%, while 42% of the simulated retina fluorescence is preserved. Thus, we recommend the implementation of Schweitzer's principle in scanning laser ophthalmoscopes used for fundus autofluorescence measurements, especially the FLIO device, for improved image quality.

Das induktiv gekoppelte Plasma (ICP) eignet sich unter atmosphärischen Bedingungen besonders für das Aufschmelzen und Verdampfen von Werkstoffen. Das elektrodenlose ICP kann ohne Ausnahme mit beliebigen Gasgemischen betrieben werden. Mit der Verwendung eines Argon-Sauerstoff Hüllgasgemisches des ICP werden Reaktion metall-organischer, flüssiger Precursoren, die in den heißen Plasmakern injiziert werden, nanokristalline Schichten erzeugt. Für den Beschichtungsprozess wir ein Ü berschallplasmastrahl eingesetzt. Durch den Aufprall der Partikel auf dem Substrat, das direkt am Düsenausgang des Plasmatrons positioniert ist, werden dünne Schichten hoher Dichte mit Kristallitgrössen von 30-40 nm erzeugt. Die Struktur und Korngrössen der abgeschiedenen Schichten werden mittels XRD analysiert.Schlagworte: Termisches HF-Plasma, nanokristalline Schichten, Ü berschallplasmastrahl, Titandioxid (TiO 2 ), PerowskitThe Inductively Coupled Plasma (ICP) at atmospheric pressure is particularly suited for melting and evaporation of materials. The electrodeless ICP can be generated without limitation of the kind of plasma forming gases. Therefore, using an argon-oxygen gas mixture as sheath gas of the ICP nanophase coatings can be processed by synthesis with metal-organic liquid precursors injected in the hot plasma core. For depositions, the plasma jet has to be supersonic. For particles which impinge onto the substrate placed near the nozzle exit of the plasma torch thin and dense coatings are obtained with crystallite sizes of 30-40 nm. The composition and the grain size of as-deposited coatings are analyzed by XRD.

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In the last 20 years, the role of ultrashort pulsed lasers in ophthalmology has become increasingly important. However, it is still impossible to guide ultra-short laser pulses with standard glass fibres. The highly energetic femtosecond pulses would destroy the fibre material, and non-linear dispersion effects would significantly change beam parameters. In contrast, photonic crystal fibres mainly guide the laser pulses in air, so that absorption and dispersive pulse broadening have essentially no effect. This article compares classical beam guidance with mirrors, lenses and prisms with photonic crystal fibres and describes the underlying concepts and the current state of technology. A classical mirror arm possesses more variable optical properties, while the HCF (Hollow-Core Photonic Crystal Fibre) must be matched in terms of the laser energy and the laser spectrum. In contrast, the HCF has more advantages in respect of handling, system integration and costs. For applications based on photodisruptive laser-tissue interaction, the relatively low damage threshold of photonic crystal fibres compared to classic beam guiding systems is unacceptable. If, however, pulsed laser radiation has a sufficiently low peak intensity, e.g. as used for plasma-induced ablation, photonic crystal fibres can definitely be considered as an alternative solution to classic beam guidance.