Introduction The work described here involved the use of a modified fundus camera to obtain sequential hyperspectral images of the retina in 14 normal volunteers and in 1 illustrative patient with a retinal vascular occlusion. Methods The paper describes analysis techniques, which allow oximetry within retinal vessels; these results are presented as retinal oximetry maps. Results Using spectral images, with wavelengths between 556 and 650 nm, the mean oxygen saturation (OS) value in temporal retinal arterioles in normal volunteers was 104.3 ( ± 16.7), and in normal temporal retinal venules was 34.8 (±17.8). These values are comparable to those quoted in the literature, although, the venular saturations are slightly lower than those values found by other authors; explanations are offered for these differences. Discussion The described imaging and analysis techniques produce a clinically useful map of retinal oximetric values. The results from normal volunteers and from one illustrative patient are presented. Further developments, including the recent development of a 'snapshot' spectral camera, promises enhanced non-invasive retinal vessel oximetry mapping.

We describe the use of wavefront coding for the mitigation of optical aberrations in a thermal imaging system. Diffraction-limited imaging is demonstrated with a simple singlet which enables an approximate halving in length and mass of the optical system compared to an equivalent two-element lens.

There was reasonable agreement between the measured oxygen saturation values and those calculated by the oximetry model. The oximetry model could be used to determine the functional health of the retina.

Purpose To determine whether there are differences in retinal vascular oxygen saturation measurements, estimated using a hyperspectral fundus camera, between normal eyes and treated eyes of subjects with asymmetrical primary open-angle glaucoma (POAG). Methods A noninvasive hyperspectral fundus camera was used to acquire spectral images of the retina at wavelengths between 556 and 650 nm in 2-nm increments. In total, 14 normal eyes and both eyes of 11 treated POAG subjects were imaged and analyzed using algorithms that use the spectral variation of the optical densities of blood vessels to estimate the oxygen saturation of blood within the retinal vasculature. In the treated POAG group, each of the eyes were categorized, based on the mean deviation of the Humphrey visual-field analyzer result, as either more-advanced or less-advanced, glaucomatous eyes. Unpaired t-tests (twotailed) with Welch's correction were used to compare the mean oxygen saturation between the normal subjects and the treated POAG subgroups. Results In less-advanced and moreadvanced-treated POAG eyes, mean retinal venular oxygen saturations (48.2 ± 21.6% and 42.6 ± 18.8%, respectively) were significantly higher than in normal eyes (27.9 ± 9.9%; P ¼ 0.03 and 0.01, respectively). Arteriolar oxygen saturation was not significantly different between normal eyes and treated POAG eyes. ConclusionsThe increased oxygen saturation of the retinal venules in advancedtreated POAG eyes may indicate reduced metabolic consumption of oxygen in the inner retinal tissues.

We describe the mapping of the optical transfer function (OTF) of an incoherent imaging system into a geometrical representation. We show that for defocused traditional and wavefront-coded systems the OTF can be represented as a generalized Cornu spiral. This representation provides a physical insight into the way in which wavefront coding can increase the depth of field of an imaging system and permits analytical quantification of salient OTF parameters, such as the depth of focus, the location of nulls, and amplitude and phase modulation of the wavefront-coding OTF. The optical transfer function (OTF) is a critical parameter of aberrated optical systems. Except in restricted cases, such as when the well-known Fouriertransform relationships are valid, 1 the numerical methods of wave-optics analysis can obscure the underlying physical processes of OTF formation. We show here how a geometrical analysis of a phasor representation of a decomposed OTF enables an improved description and quantification of OTF parameters to be made. Although this approach is pertinent to all aspects of incoherent image formation, its application to wavefront coding 2 (WC) is of particular interest. When it is combined with digital postprocessing, a WC mask placed in the pupil plane of a conventional imager produces greatly reduced sensitivity to defocus-related optical aberrations.2-4 The resultant OTFs are approximately invariant over a restricted range of defocus, but there has been no reported analytical treatment of the range of defocus invariance, of the magnitude of departures from invariance, or of a physical, wave-optics explanation of the underlying physical processes. In this Letter we demonstrate that the OTF of a defocused WC system can be considered in terms of a generalized Cornu spiral (GCS) and that the performance parameters of a WC system can be readily derived from the geometry of such a spiral. We start by describing how the OTF can be decomposed to enable its composition to be plotted as a curve in the complex plane. We then apply this technique to an imaging system, incorporating first defocus and then both defocus and a cubic phase function.Consider first the decomposition of the OTF: For clarity the analysis is restricted to the case of a onedimensional optical system. The OTF, L͑f͒, for spatially incoherent illumination is determined by the normalized autocorrelation of the pupil function, P͑x͒:where x is the transverse linear coordinate, R f/ f max is a pupil-plane coordinate representing spatial frequency f, R is the transverse half-width of the pupil, and f max is the cutoff spatial frequency. We define the integralwith h͑r , v͒ = P͑r + v͒P * ͑r − v͒ and h͑r ,0͒ = ͉P͑r͉͒ 2 , where r = x / R is the normalized pupil coordinate and v = f / f max is the normalized spatial frequency. The normalized OTF is L͑v͒ = H͑1−v , v͒ − H͑−1 + v , v͒. We now decompose the OTF, L͑f͒, into phasor components, h͑r , v͒. We represent incremental contributions hdr in the complex plane and perform the integral in Eq. (2) as rЈ is ...