Hemoglobin measurement by retinal imaging

A non-transitory computer readable medium comprising computer-executable instructions that, when executed by a computer, cause the computer to perform a method comprising:

• receiving a plurality of backscattered reflection intensities resulting from illuminating a retinal tissue having blood vessels by light including two isosbestic wavelengths, wherein the isosbestic wavelengths correspond to isosbestic points where oxyhemoglobin and deoxyhemoglobin have a same molar extinction coefficient, wherein the plurality of backscattered reflection intensities are:
• spectrally resolved at least for the two isosbestic wavelengths, and
• position-resolved for at least a blood vessel location coinciding with a selected blood vessel and a tissue location coinciding with a retinal tissue without a blood vessel;
• and
• calculating the hemoglobin concentration as a quantity representing a sum total of oxyhemoglobin and deoxyhemoglobin per unit volume of blood based on a combination of measurements of the plurality of backscattered reflection intensities at the two isosbestic wavelengths, each being position-resolved for the blood vessel location and the tissue location.

A system for measuring hemoglobin concentration, the system comprising:

• a light source configured to illuminate a retinal tissue having blood vessels by light including two isosbestic wavelengths, wherein the isosbestic wavelengths correspond to isosbestic points where oxyhemoglobin and deoxyhemoglobin have a same molar extinction coefficient;
• collection optics configured to receive a plurality of backscattered reflection intensities, wherein the plurality of backscattered reflection intensities are:
• spectrally resolved at least for the two isosbestic wavelengths, and
• position-resolved for at least a blood vessel location coinciding with a selected blood vessel and a tissue location coinciding with the retinal tissue without a blood vessel;
• and
• a processor programmed to calculate the hemoglobin concentration based on a combination of measurements of the plurality of backscattered reflection intensities at the two isosbestic wavelengths, each being position-resolved for the blood vessel location and the tissue location.