Oximetry and blood flow in the retina

We present the development of setup composed of a retinal oximeter and a blood velocimeter implemented on a regular fundus ophthalmoscope. The oximeter part can acquire nine wavelength-dependent sub-images of the patient fundus in a single snapshot. The fundus image is projected on a large format CCD by an array of nine lenses and wavelength selection is provided by a filter array. Higher wavelength images help establishing melanin absorption, which is further extrapolated to shorter wavelength and subtracted from the absorption images. The remaining shorter wavelength subimages are used measure the oxygen saturation in the retina by fitting oxy- and deoxy-hemoglobin absorption curves. The setup was calibrated with optical phantoms of know optical properties. The velocimeter part of the setup relies on following clusters of erythrocytes to assess the velocity of blood.