Imaging spectroscopy of the human ocular fundus in vivo

Hammer, Martin; Schweitzer, Dietrich; Leistritz, Lutz; Scibor, M.; Donnerhacke, Karl‐Heinz; Strobel, J

doi:10.1117/12.285093

Cited by 23 publications

(14 citation statements)

References 21 publications

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“…This goes beyond dual wavelength oximetry and, thus, enables measurements not only in ophthalmoscopically visible vessels but also in capillaries that cannot be resolved optically. On the other hand, our technique does not need the recording of full spectra as described earlier [42,[45][46][47]. In contrast to the three wavelength method, described by Delori [48], our approach compensates for perturbations like melanin absorption and light loss by scattering [38].…”

Section: Discussionmentioning

confidence: 99%

Optic disc blood perfusion and oxygenation in glaucoma

Zoubi

Riemer²,

Simon

et al. 2022

Graefes Arch Clin Exp Ophthalmol

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Purpose To investigate the haemoglobin concentration and oxygenation in the optic disc in glaucoma patients vs. controls. Methods Thirty-one eyes of primary open angle glaucoma patients (mean age: 64.9 ± 2.1 years) and 31 eyes of 31 healthy controls (65.5 ± 2.0 years) were included. Perimetry, optical coherence tomography (OCT), and OCT angiography were performed. Multispectral imaging was used to record the optic disc reflectance at wavelengths 522 nm, 548 nm, 555 nm, 586 nm, and 610 nm, and haemoglobin concentration and oxygenation (SO2) were calculated from these measures. This was done in the rest and under stimulation of neuronal activity by flicker light. Results The haemoglobin concentration was significantly lower (p < 0.001) in the rim (40.0 ± 6.3) and the excavation (35.7 ± 8.0) of the glaucoma patients’ discs than in controls (45.7 ± 7.5). SO2 was not different in general, but lower in a subgroup of 18 glaucoma patients with ischaemic disc rims than in non-ischaemic ones (median 26.8%, interquartile range (IQR): 29.5% vs. 51.9%, IQR 32.0%, p = 0.02) as well as in controls (41.0%, IQR 30.6%, p = 0.01). Flicker light stimulation significantly increased the haemoglobin concentration in the controls (+ 1.3 ± 3.6, p = 0.048) as well as in the rim of glaucoma discs (+ 2.6 ± 5.0, p = 0.006) and SO2 in the controls only (+ 15.4 ± 23.6%, p = 0.001). The haemoglobin concentration was significantly correlated with the perimetric mean defect, retinal nerve fibre layer (RNFL) thickness and para-papillary perfusion density. Conclusions The optic disc haemoglobin concentration and oxygenation are quantifiable from multispectral imaging and reduced in glaucoma. The correlation of haemoglobin concentration with perfusion density, RNFL thickness and visual field loss indicates its implication in glaucoma pathology.

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Section: Discussionmentioning

confidence: 99%

Optic disc blood perfusion and oxygenation in glaucoma

Zoubi

Riemer²,

Simon

et al. 2022

Graefes Arch Clin Exp Ophthalmol

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“…To achieve this, an aperture in the image plane of the retina was used to define the sampling area. Hammer et al used a slit-shaped stop in an image plane of the eye fundus to acquire reflectance spectra of horizontal areas [18]. Diaconu and Vucea et al proposed a system using a holed-mirror located in an image plane to reflect light coming from the fundus to a camera with the same intent [19], [20].…”

Section: Introductionmentioning

confidence: 99%

Targeted spectroscopy in the eye fundus

Lapointe¹,

Akitegetse²,

Poirier³

et al. 2023

Preprint

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Significance: The assessment of biomarkers in the eye is rapidly gaining traction for the screening, diagnosis and monitoring of ocular and neurological diseases. Targeted ocular spectroscopy is a new technology that enables the user to concurrently image the eye fundus and acquire high quality spectra from a targeted region - 1.5 degrees - within the imaged area. The combination of imaging and high-sensitivity spectroscopy provides structural, compositional, and functional information of selected regions of the eye fundus. This opens the door to new, non-invasive approaches to the detection of biomarkers in the eye. Aim: The aim of this study was to demonstrate the multi-modal functionality and validation of the targeted ocular spectroscopy developed. This was done in vitro, using a reference target and a model eye, and in vivo. Approach: Images and spectra from different regions of a reference target and a model eye were acquired and analyzed to validate the system. The same eye model was used to obtain fluorescence images and spectra, highlighting the capability of the system to also perform targeted ocular fluorescence spectroscopy. Subsequently, in vivo imaging and diffuse reflectance spectra were acquired to assess blood oxygen saturation in the optic nerve head and the parafovea of healthy subjects. Results: Tests conducted with the reference target showed that spectral analysis could be accurately performed within specific areas of the imaging space. Moving to the model eye, distinct spectral signatures were observed for the targeted spectral analysis done in the optic disc, the retina and the macula, consistent with the variations in tissue composition and functions between these regions mimicked by the model eye. Further, it was shown that the targeted spectral analysis could also be performed in a fluorescence mode to distinguish various fluorophores present within the imaging space. Finally, in vivo ocular oximetry experiments performed in the optic nerve head and parafovea of healthy patients showed significant differences in blood oxygen saturation between these regions (p = 0.004). Conclusions: Enabling non-invasive, sensitive diffuse reflectance and fluorescence spectroscopy in specific regions of the eye fundus opens the door to a whole new range of monitoring and diagnostic capabilities, from assessment of oxygenation in glaucoma and diabetic retinopathy to photo-oxidation and photo-degradation in age-related macular degeneration.

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“…There is a growing body of retinal spectroscopy, for example, where this problem may become an issue. [4][5][6] This paper examines the relation between optical scattering and some realistic constraints in the case of a spectral imaging system and a backscattering target. We restrict our investigation to a single species in order to concentrate on effects arising from photon trajectory distributions.…”

Section: Introductionmentioning

confidence: 99%

“…Fig 5. Backscatter from the center of illuminated disks of several diameters, at three representative wavelengths.…”

mentioning

confidence: 99%

Consequences of scattering for spectral imaging of turbid biologic tissue

et al. 2000

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Spectral imaging permits two-dimensional mapping of the backscattering properties of biological systems. Such mapping requires broadband illumination of the entire area of interest. However, imaging of turbid biological media under these conditions often involves mean photon path lengths that exceed the pixel size. Using a numerical Monte Carlo model, we have studied the effects of photon scattering in a hemoglobin-bearing model system. We find that photon migration and the resulting wavelength-dependent optical coupling between pixels can complicate the analysis of imaging spectroscopy data. In fact, the wavelength dependence of photon trajectories also alters the distribution of photon exit angles at the tissue surface. We therefore find that the finite optical field of view of an imaging spectrometer can affect the measured spectra in the absence of chromatic aberrations.

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Imaging spectroscopy of the human ocular fundus in vivo

Cited by 23 publications

References 21 publications

Optic disc blood perfusion and oxygenation in glaucoma

Optic disc blood perfusion and oxygenation in glaucoma

Targeted spectroscopy in the eye fundus

Consequences of scattering for spectral imaging of turbid biologic tissue

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