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D. J. Mordant, I. Al Abboud, A. R. Harvey, A. I. McNaught; Hyperspectral Imaging of the Human Retina - Oximetric Studies. Invest. Ophthalmol. Vis. Sci. 2007;48(13):148.
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Hyperspectral imaging of the human retina is a relatively new concept that has the potential to determine the metabolic status of the retina. Oximetric studies have been the main focus of research with the use of hyperspectral technology as the spectral characteristics of the two functional haemoglobin derivatives are well known. However, there is much debate as to the accuracy of quantitative oximetric measurements because of several main confounding factors that influence reflectance spectroscopy. This study aims to determine the variation in the oxygen saturations in the retina amongst normal patients and in patients with retinal arteriopathy.
A hyperspectral retinal imaging system consisting of a modified fundus camera, a liquid crystal tuneable filter and a low noise CCD was used to capture hyperspectral human retinal images. A hyperspectral data cube with a spectral bandwidth of 500nm to 700nm and a spectral resolution of 10nm at wavelength steps of 2nm were obtained for each subject. Normal subjects (n= 15) and subjects with retinal arterial occlusions (n = 3) were examined. Reflectance spectral analysis and linear spectral unmixing algorithms were used to determine the oximetric status of the retina.
Linear spectral unmixing algorithms produced consistent oximetric maps of the retina in normal subjects. In subjects with arterial occlusions, this technique was able to detect changes in the oximetric status of the retinal arterioles, optic discs and choroidal circulation. In particular, one of these subjects with arteritic retinal vasculopathy caused by giant cell arteritis demonstrated a significant improvement in the retinal, optic disc and choroidal oxygenation following treatment with intravenous methylprednisolone.
Hyperspectral imaging is capable of accurately detecting of hypoxic changes in the retina and monitoring its response to treatment. This holds much promise for its application in detecting circulatory changes in diabetic retinopathy and glaucoma.
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