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D. Link, B. U. Seifert, G. Henning, W. Vilser; Universal Retina Camera (URC) for Adaptive Retinal Vessel Analysis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2580.
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To obtain an innovative device for adaptive retinal vessel analysis an experimental set-up was realised. The adaptivity relates to functional, metrological, and individual, that means patient eye aligned, properties. Thus, investigation of microcirculation gets an improvement for a better diagnostic analysis by doing no changes referring to the optics (no different optical/ophthalmological devices) because of a free programmable optical path.
A standard fundus camera (VISUCAM lite, Carl Zeiss Meditec AG) was used to provide the optical framework. The two critical optically effective planes of the fundus camera were made accessable. First there is the plane conjugated optically to the anatomic pupil (PP) and second the conjugated plane to the human fundus (FP). Both physical planes of the fundus camera were replaced by Spatial Light Modulators (SLM). Thereby, it was possible to realise the programmable optical path. The temporal and spatial light modulation are accomplished by a DMD (PP conjugated) and a transmissive LCD (FP conjugated). The SLMs were controlled by a standard VGA interface. Accompanying the implementation of the SLMs dimensioning and simulations with ZEMAX were performed.
There was build up an operative demonstrator system. Both anatomic planes, PP and FP, are freely modulatable. These effects are demonstrated and documented by means of an artificial eye to have approximate realistic conditions in the FP and a CCD camera attached to the fundus camera for live imaging. In the PP there were put into effect e.g. variable annulus diameters and segments, and spots according to Scheiner stops. On the FP there were structures imaged such as rectangulars, spots, checkerboards, and fixation marks. All patterns can be combined and modulated over time in the PP as well as in the FP.
As the results show, the developed set-up offers an enormous field of application certainly not limited to retinal vessel analysis. Although there are optical aberrations due to the not conformed optical design and given geometrical conditions the intented aim is reached and the effects of two-plane modulation is displayed. The adjustable spot diameter offers the chance to decrease the light exposure of the patient's eye. Stimulations, for instance a macula flicker, can be applied locally and consequently very effectively connected with an eye movement correction. Further investigations have to be done to demonstrate the opportunities and drawbacks more detailed.
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