Hyperspectral imaging of the retina presents a unique opportunity for direct and quantitative mapping of retinal
biochemistry - particularly of the vasculature where blood oximetry is enabled by the strong variation of absorption
spectra with oxygenation. This is particularly pertinent both to research and to clinical investigation and diagnosis of
retinal diseases such as diabetes, glaucoma and age-related macular degeneration. The optimal exploitation of
hyperspectral imaging however, presents a set of challenging problems, including; the poorly characterised and
controlled optical environment of structures within the retina to be imaged; the erratic motion of the eye ball; and the
compounding effects of the optical sensitivity of the retina and the low numerical aperture of the eye. We have
developed two spectral imaging techniques to address these issues. We describe first a system in which a liquid crystal
tuneable filter is integrated into the illumination system of a conventional fundus camera to enable time-sequential,
random access recording of narrow-band spectral images. Image processing techniques are described to eradicate the
artefacts that may be introduced by time-sequential imaging. In addition we describe a unique snapshot spectral imaging
technique dubbed IRIS that employs polarising interferometry and Wollaston prism beam splitters to simultaneously
replicate and spectrally filter images of the retina into multiple spectral bands onto a single detector array. Results of
early clinical trials acquired with these two techniques together with a physical model which enables oximetry map are reported.
Spectral imaging of the retina shows great promise for the early detection of retinal disease through retinal screening
programs. Implementation of such a program will require instrumentation capable of efficiently recording the requisite
spectral data cube. We report on the development of two candidate approaches: one employs a traditional liquid crystal
tunable filter to filter the illumination source and enable the spectral data cube to be assembled from mutually
coregistered narrow-band images recorded in time sequence: the second employs, IRIS, a novel image replicating
imaging spectrometer to record a two-dimensional spectral data cube in a single snapshot.
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