Abstract
A Monte Carlo simulation of light propagation through the retina has been developed to understand the path-length distributions within the retinal vessel. For full-field illumination, the path-length distribution within the vessel comprises directly backscattered light and light that has passed once or twice through the vessel. The origins of these light path-length distributions can be better understood by investigating different combinations of single-point illumination and detection positions. Perhaps the most significant observation is that illumination at the edges of the vessel, rather than over the whole field of view, and detection directly above the vessel capture only the light that has taken a single pass through the vessel. This path-length distribution is tightly constrained around the diameter of the vessel and can potentially provide enhancements for oxygen saturation imaging. The method could be practically implemented using an offset-pinhole confocal imaging system or structured light illumination.
Highlights
The measurement of oxygen saturation in retinal vessels is useful as a diagnostic aid in a number of ocular vascular disorders such as glaucoma,[1] diabetic retinopathy,[2] and central retinal vein occlusion,[3] where hypoxia of the retina and optic-nerve head[4,5,6] are believed to contribute
We describe a Monte Carlo simulation of light propagation through a retinal vessel located above a homogeneous fundus
To assess the validity of the Monte Carlo simulation developed, the results were compared with images of an eye phantom obtained from a hyperspectral fundus camera
Summary
The measurement of oxygen saturation in retinal vessels is useful as a diagnostic aid in a number of ocular vascular disorders such as glaucoma,[1] diabetic retinopathy,[2] and central retinal vein occlusion,[3] where hypoxia of the retina and optic-nerve head[4,5,6] are believed to contribute. Spectral imaging is potentially a useful tool for making reliable measurements of oxygen saturation in the human ocular fundus; a deeper understanding of light propagation from the illumination source through the various layers of the retina and to the detector is needed to enable these measurements to be made accurately.[7]. An important aspect of making accurate oxygen saturation measurements is an understanding of light paths within the retina. Due to the high levels of scattering within the retina, the path-lengths of light that has propagated through blood vessels are diverse with photons generally passing through various tissues and structures with different flight times through each
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