A method and device for differentiating a blood absorption contribution and an absorption contribution by other optical structures of a patient's eye to a full spectral retinal reflectometry absorption function, perform reflectometry absorption measurement on the vessels of the patient's retina at a first number of wavelengths in the visible spectral area, corresponding to isosbestic points where hemoglobin and oxyhemoglobin present similar absorption coefficients. The absorption contribution by the other optical structures of the patient's eye at each wavelength is estimated as a difference between the reflectometry absorption measurement and a weighting parameter that amplifies the hemoglobin absorption coefficient. The weighting parameter is adjusted so that points representing the differences are collinear when representing these points on a logarithmic scale of the wavelengths. Also a method and device for evaluating blood oxygenation in vessels of a patient's retina, comprises the above absorption contribution differentiating method. The blood oxygenation evaluating method and device perform reflectometry absorption measurement on the vessels of the patient's retina at a second number of wavelengths where a ratio between the absorption coefficients of the hemoglobin and oxyhemoglobin presents a local maximum, and derive blood oxygenation values of the vessels of the patient's retina from at least a portion of the reflectometry absorption measurements and the absorption contributions.L'invention concerne un procédé et un dispositif permettant de différencier une contribution de l'absorption par le sang d'une contribution de l'absorption par d'autres structures optiques de l'œil d'un patient à une fonction d'absorption de réflectométrie rétinienne spectrale complète, d'effectuer une mesure d'absorption de réflectométrie sur les vaisseaux de la rétine du patient à un premier nombre de longueurs d'onde dans la région du spectre visible correspondant aux points iso
