In Situ Analysis of Fundus Blood Flow - Real Time Measurements of Blood Vessel and System Development -

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The purpose of this study is to develop an optical method for real time measurements of retinal vessel diameter and to establish the in situ analyzing system of fundus blood flow by combining with the laser retinal blood flowmeter. Some topical results are reviewed below.1. To measure the retinal spectral reflectance, an experimental apparatus was constructed by using a fundus camera, white light source, optical fiber, and multi-channel spectrometer.2. Analysis of the retinal spectral reflectance measured from human subjects was carried out to determine the optimum wavelength of the light source to be 5 70 nm for high-contrast imaging of vessels. A new method was proposed for optical discrimination of artery and vein using color perception.3. A unit for measuring retinal vessel diameters was developed by using a linear image sensor. In this unit, the scanning time of the sensor was set to be 125 msec and vessels may be imaged over a region of 25-50 pixels on the sensor.4. To determine successfully the vessel diameter from signals of the linear image sensor, a signal-processing software was newly developed by means of the moving average and differentiation of pixel data.5. A calibration test was conducted to the measuring unit. Then, this method was compared with the vessel analysis of video images, and results showed the usefulness of this method.6. The unit for measuring retinal vessel diameters was combined with the laser retinal blood flowmeter, and some software programs were modified to measure simultaneously the blood flow velocity, vessel diameter, and blood flow rate in a real time manner. Finally, the in situ analyzing system of fundus blood flow was established by installing some additional functions.The color perception method for vessel discrimination proposed in this study may potentially be useful for oxygen saturation measurements.