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P. Lemaillet, J. C. Ramella Roman, Q. Nguyen; Construction of a Dynamic Eye Phantom for Retinal Oximetry Measurements. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3295.
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Measurements of oxygen saturation in the retina can yield information about the onset of eye pathologies. Calibration of a retinal oximeter is difficult due to the layered structure of the eye and the lack of alternative measurement techniques. The study is designed to develop an artificial eye mimicking structures of the ocular fundus with a dynamical oxygen supply that could be used in the investigation of light transport in the retina.
The artificial eye is composed of a retina vessel and 3 layers: the choroid, the RPE, and the sclera. The sclera is represented by a Spectralon slab; the optical properties of the other layers are mimicked using titanium dioxide and ink. Epoxy is used as a supporting structure. The optical thickness of each layer of the eye phantom matches the respective ocular layers. The retinal vasculature is simulated with a micro-tube connected to a pump and a hemoglobin (Hb) reservoir in a closed circulatory system; hemoglobin oxygenation in the vessel can be altered using a reversible fuel cell.
Monte Carlo simulations of the reflectance for a two-layer model of the eye (RPE and a bloodless choroid) were computed for the eye phantom and the eye fundus, showing the validity of the eye phantom (left image). Vessel oxygen was estimated by spectrometric measurements, starting from fully deoxygenated bovine hemoglobin. There was a noticeable transition from a classic deoxygenated Hb curve to the two maxima oxygenated Hb curves (right image). The resulting oxygen saturation was computed using the Delori's equation.
An artificial eye mimicking the structure and optical properties of the eye was developed for retinal oximetry measurements. Diffused reflectance of both eye phantom and eye fundus was computed using Monte Carlo simulations and closely matched experimental values.
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