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Noninvasive measurement of oxygen saturation in optic-nerve head tissue

We describe a non-invasive in vivo hyperspectral imaging technique for visualizing the spatial distribution of retina and optic nerve head (ONH) tissue oxygenation. Real time images of the fundus are acquired with continuous wavelengths (410-918 nm) to generate a data cube consisting of one spectral and two spatial dimensions. Reflected light from the one-dimensional (1-D) area of the sample is first passed through a grating and is then imaged onto a 12-bit silicone charge- coupled device (CCD) detector. A scanner then proceeds to the next 1-D area of the sample. Acquired image frames contain 256 spatial pixels and 256 wavelengths along rows and columns. Image sequences are scanned along the perpendicular spatial dimension using the push-broom method, whereby the spectrograph and camera are translated under constant velocity with respect to the fundus camera image over 6.6 mm of travel. This set of acquired images contains the full reflected light spectrum at each pixel of a two dimensional area of the retina and ONH. The system employs a focal plane scanner (FPS) using a linear actuator to provide motion. An algorithm processes spectral information at each pixel to represent the varying spatial distribution of retina and ONH tissue oxygenation. Imaging data are obtained from ONH tissue at both normal intraocular pressure (IOP) and acutely raised IOP.