Heidelberg Retina Flowmeter (HRF)

• confocal laser scanning and laser Doppler flowmetry
• no pupil dilation is necessary
• data acquisition time is 2 seconds
• two-dimensionally resolved perfusion maps are computed allow quantifying the local values of flow, volume, and velocity of the red blood cells
• operation software runs on a standard personal computer
• database handling, image acquisition, image processing, image contrast enhancement, printout of examination reports with color or black/white printers, and image archiving

The Heidelberg Retina Flowmeter uniquely merges two sophisticated measurement techniques, confocal laser scanning and laser Doppler flowmetry, to a new kind of instrument that provides non-invasive two-dimensional mapping of the retinal micro-circulation.

Using an infrared laser, the retina or optic disc is scanned two-dimensionally. Light reflected or scattered at moving objects is frequency shifted due to the optical Doppler effect. It interferes with unchanged light reflected at surrounding tissue. The interference causes characteristic temporal intensity variations of the measurable reflected light intensity. The Heidelberg Retina Flowmeter measures this temporal intensity variation at each point in the two-dimensional scan field by multiple scanning. The Doppler frequency shift of the reflected light is computed from the acquired data and used to quantify the local velocity of moving particles. The excellent performance of this technique allows to resolve blood flow in individual capillaries.