|
Measurements of oxygen saturation and flow in the retina can yield information about the eye health and the
onset of eye pathologies such as Diabetic Retinopathy. Recently we have realized an instrument capable of
measuring oxygenation in the retina using six different wavelengths and capable of measuring blood flow using
speckle-based techniques. The calibration of such instrument is particularly difficult due to the layered structure
of the eye and the lack of alternative measurement techniques. For this purpose we have realized an in vitro
model of the human eye. The artificial eye is composed of four layers: the retina vessels, the choroids, the retinal
pigmented epithelium (RPE), and the sclera. The retina vessels are modeled with 150 μm tube connected to a
micro-pump delivering 34 μl/min. The micro-tube, the pump, and a blood reservoir were connected in a closed
circulatory system; blood oxygenation in the vessel could be modified using an external oxygen reservoir. The
optical properties of all other layers were mimicked using titanium dioxide as a scatterer and ink as an absorber.
The absorption coefficient μa and the scattering coefficient µs of these layers were independently measured using
an integrating sphere. Absorption and scattering coefficient of all layers were modified before experimental
measurements and a Monte Carlo program was finally used to model the experimental results.
|
