Monte-Carlo simulation and tissue-phantom model for validation of ocular oximetry

Akitegetse, Cleophace; Landry, Patricia; Robidoux, Jonathan; Lapointe, Nicolas; Brouard, Danny; Sauvageau, Dominic

doi:10.1364/boe.458079

Cited by 9 publications

(8 citation statements)

References 60 publications

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“…This was performed as a demonstration of a concrete application stemming from targeted spectral analysis and not as a validation of ocular oximetry per se. StO2 was calculated based on previously described methods 26 , 32 for each acquired spectrum and averaged over the acquisition at a specific location for each subject. The difference in average StO2 in the parafovea (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…An ocular oximetry algorithm, previously developed for the determination of blood oxygen saturation in the tissues of the eye fundus (StO2), 26 was used to process diffuse reflectance spectra acquired in vivo . This algorithm is based on the modified Beer–Lambert law and includes contributions from erythrocyte light scattering, 28 a scaling term, retinal melanin, the crystalline lens, oxyhemoglobin, and deoxyhemoglobin.…”

Section: Methodsmentioning

confidence: 99%

“…Demonstrations of diffuse reflectance in the visible range ( in vitro and in vivo ) and fluorescence ( in vitro ) were performed. In vivo ocular oximetry assessments were also performed in healthy patients using previously established algorithms 26 …”

Section: Introductionmentioning

confidence: 99%

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Targeted spectroscopy in the eye fundus

Lapointe,

Akitegetse,

Poirier

et al. 2023

J. Biomed. Opt.

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.SignificanceThe 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 technology that enables concurrent imaging of the eye fundus and analysis of high-quality spectra from a targeted region within the imaged area. This provides structural, compositional, and functional information of specific regions of the eye fundus from a non-invasive approach to ocular biomarker detection.AimThe aim of our study was to demonstrate the multimodal functionality and validation of targeted ocular spectroscopy. This was done in vitro, using a reference target and a model eye, and in vivo.ApproachImages and spectra from different regions of a reference target and a model eye were acquired and analyzed to validate the system. Targeted ocular fluorescence spectroscopy was also demonstrated with the same model. 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.ResultsTests conducted with the reference target showed accurate spectral analysis within specific areas of the imaging space. In the model eye, distinct spectral signatures were observed for the optic disc, blood vessels, the retina, and the macula, consistent with the variations in tissue composition and functions between these regions. An ocular oximetry algorithm was applied to in vivo spectra from the optic nerve head and parafovea of healthy patients, showing significant differences in blood oxygen saturation. Finally, targeted fluorescence spectral analysis was performed in vitro.ConclusionsDiffuse reflectance and fluorescence spectroscopy in specific regions of the eye fundus open 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 photodegradation in age-related macular degeneration.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Targeted spectroscopy in the eye fundus

Lapointe,

Akitegetse,

Poirier

et al. 2023

J. Biomed. Opt.

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“…In fact, spectra from the ONH displayed a stronger contribution from hemoglobin components; the nerve fibers, which are the main constituents of the ONH [57] act as diffusers for the main local absorber, which is hemoglobin. The thickness of the different layers of the eye fundus, the contribution of the choroid and the photoreceptor cell density are other factors that can contribute to spectral variations between regions [29].…”

Section: Discussionmentioning

confidence: 99%

“…Data acquired from human subjects underwent additional processing to derive oxygen saturation (StO2). The process for correcting spectra and calculating oxygen saturation has been described elsewhere [29].…”

Section: Data Processingmentioning

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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