Choroidal Oximetry With a Noninvasive Spectrophotometric Oximeter

Kristjánsdóttir, Jóna Valgerður; Hardarson, Sveinn Hákon; Harvey, Andrew R.; Ólafsdóttir, Ólöf Birna; Eliasdottir, Thorunn Scheving; Stefánsson, Einar

doi:10.1167/iovs.12-10507

Cited by 17 publications

(26 citation statements)

References 20 publications

(31 reference statements)

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“…Furthermore, a higher haemoglobin oxygen saturation level in the vessels of the choroid, when compared with the vessels of the retina, and further rise in that difference with inhalation of 100% oxygen, was demonstrated in vivo in human subjects using a non‐invasive spectrophotometric oximeter (Kristjansdottir et al. ). Unlike the retinal circulation, the choroidal circulation consists of fenestrated blood vessels due to the continuous secretion of VEGF by the RPE cells (Blaauwgeers et al.…”

Section: Anatomy and Physiology Of The Choroidmentioning

confidence: 99%

Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema

Campos

Martins

et al. 2016

Acta Ophthalmologica

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Diabetic macular oedema (DMO) is the leading cause of vision loss in the working-age population. Blood-retinal barrier (BRB) dysfunction in diabetic retinopathy (DR), mainly at the level of the retinal vessels, has long been related with leakage and fluid accumulation, leading to macular oedema. However, the nourishment of the macula is provided by the choroid and a diabetic choroidopathy has been described. Therefore, there has been a growing interest in studying the role of the choroid in the pathophysiology of DR and DMO, mainly by optical coherence tomography (OCT). Nevertheless, there are conflicting results in the different studies. We summarize the results from the available studies, describe the limitations and confounding factors and discuss future procedures to avoid bias.

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Section: Anatomy and Physiology Of The Choroidmentioning

confidence: 99%

Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema

Campos

Martins

et al. 2016

Acta Ophthalmologica

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“…These systems produce automatic oxygen saturation maps, but are limited to retinal vessels. Oximetry of choroidal vessels with the Oxymap T1 can be done for lightly pigmented individuals, but its accuracy needs refinement [13]. Geirsdottir, et al used the Oxymap T1 to demonstrate that oxygen saturation in retinal veins decreases with age in healthy eyes [12].…”

Section: Introductionmentioning

confidence: 99%

Hyperspectral Image Mapping Spectrometry for Retinal Oximetry Measurements in Four Diseased Eyes

Dwight¹,

Weng²,

Coffee³

et al. 2016

International Ophthalmology Clinics

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We describe the hyperspectral Image Mapping Spectrometer (IMS) which is able to acquire spectral images of the retina with no scanning components. We then utilize this technology to obtain absolute oxygen saturation measurements in four patients with retinal diseases. The IMS acquires spatial and spectral information of a scene in a single camera exposure time. The IMS is attached to the port of a Topcon TRC-50EX funduscopic camera in order to acquire images. The IMS has high spatial (350×350) and spectral sampling (40), and avoids motion artifacts associated with eye movements. Oximetry values are obtained by measuring the absorption of retinal blood. Four patients with different retinal diseases were imaged via the IMS in this study. Oxygen saturation is calculated using a least squares fit applied to the whole blood oximetry equation. Oxygen saturation was found to be 88.6% (±1.9) and 34.1% (±7.0) for the artery and vein, respectively, in a patient with non-exudative age-related macular degeneration (AMD) with borderline glaucoma, 100.0% (±0.0) and 50.4% (±8.2) in a patient with exudative AMD, 100.0% (±0.0) and 45.2% (±7.0) in a patient with retinitis pigmentosa, and 94.1% (±2.5) and 44.9% (±5.6) in a patient with chronic iridocyclitis. These values are consistent with previously published data. Based on spatial and spectral data, we created an oxygen saturation map with oxygenation data overlying retinal vasculature. Hyperspectral imaging may be a promising way to measure retinal oxygen saturation. IMS technology is advantageous in its ability to obtain images free of motion artifacts.

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“…Retinal oximetry measures vascular oxygen tension in inner retinal 6−9 and choroidal vasculature 10 based on hemoglobin oxygen saturation. Phosphorescence lifetime imaging measures oxygen levels using an oxygen sensitive agent that is quenched by oxygen allowing for vascular pO 2 levels to be quantified.…”

Section: Introductionmentioning

confidence: 99%

Molecular Probes for Imaging of Hypoxia in the Retina

Evans

Kim²,

Moore

et al. 2014

Bioconjugate Chem.

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Hypoxia has been associated with retinal diseases which lead the causes of irreversible vision loss, including diabetic retinopathy, retinopathy of prematurity, and age-related macular degeneration. Therefore, technologies for imaging hypoxia in the retina are needed for early disease detection, monitoring of disease progression, and assessment of therapeutic responses in the patient. Toward this goal, we developed two hypoxia-sensitive imaging agents based on nitroimidazoles which are capable of accumulating in hypoxic cells in vivo. 2-nitroimidazole or Pimonidazole was conjugated to fluorescent dyes to yield the imaging agents HYPOX-1 and HYPOX-2. Imaging agents were characterized in cell culture and animal models of retinal vascular diseases which exhibit hypoxia. Both HYPOX-1 and -2 were capable of detecting hypoxia in cell culture models with >10:1 signal-to-noise ratios without acute toxicity. Furthermore, intraocular administration of contrast agents in mouse models of retinal hypoxia enabled ex vivo detection of hypoxic tissue. These imaging agents are a promising step toward translation of hypoxia-sensitive molecular imaging agents in preclinical animal models and patients.

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Choroidal Oximetry With a Noninvasive Spectrophotometric Oximeter

Cited by 17 publications

References 20 publications

Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema

Viewing the choroid: where we stand, challenges and contradictions in diabetic retinopathy and diabetic macular oedema

Hyperspectral Image Mapping Spectrometry for Retinal Oximetry Measurements in Four Diseased Eyes

Molecular Probes for Imaging of Hypoxia in the Retina

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