Blood oxygenation measurements by multichannel reflectometry on the venous and arterial structures of the retina

The aim of the present study was to propose a model and a method to derive the oxyhemoglobin blood content in the retinal veins and arteries by full spectrum reflectometry measurements in the spectral zone from 430 to 680 nm. We proposed a mathematical equation expressed as a linear combination of two terms S(OHb)(λ) and S(Hb)(λ) representing the normalized spectral absorption functions of the hemoglobin and the oxyhemoglobin, one term λ(-n) representing the ocular media absorption with scattering, and a family of multi-Gaussian functions, which usefully compensate for the noncompatibility of the model and the experimental data in the red spectral zone. The present paper suggests that the spectral reflection function in the area from 520 to 580 nm is optimal in calculating the oxyhemoglobin concentration of the blood contained in the endothelial structures of retinal vessels. The model calculation needs a function (1/λ)(-n) that corrects for the ocular media absorption and light scattering on the vessels' structures. For the spectral area of lights with wavelength larger than 580 nm, the reflected light represents mainly the light scattering on the red blood cells.