Calibration-free measurement of the oxygen saturation in human retinal vessels

Schweitzer, Dietrich; Leistritz, Lutz; Hammer, Martin; Scibor, M.; Bartsch, Ulrich; Strobel, J

doi:10.1117/12.209850

Cited by 33 publications

(37 citation statements)

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“…Combining measurements of blood flow (Cunha-Vaz and Lima, 1978;Oswald et al, 1983;Riva et al, 1972;Sato et al, 2006;Vilser et al, 1986) and of arterial oxygen saturation (Beach et al, 1999;Delori et al, 1981;Hickham et al, 1963;Laing et al, 1975;Schweitzer et al, 1999Schweitzer et al, , 1995 the supply of the tissue with oxygen can be calculated. Additionally, the arterio-venous difference of the oxygen saturation enables an estimation of the oxygen consumption in the tissue.…”

Section: Introductionmentioning

confidence: 99%

Towards metabolic mapping of the human retina

Schweitzer

Schenke

Hammer

et al. 2007

Microscopy Res & Technique

202

240

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Functional alterations are first signs of a starting pathological process. A device that measures parameter for the characterization of the metabolism at the human eye-ground would be a helpful tool for early diagnostics in stages when alterations are yet reversible. Measurements of blood flow and of oxygen saturation are necessary but not sufficient. The new technique of auto-fluorescence lifetime measurement (FLIM) opens in combination with selected excitation and emission ranges the possibility for metabolic mapping. FLIM not only adds an additional discrimination parameter to distinguish different fluorophores but also resolves different quenching states of the same fluorophore. Because of its high sensitivity and high temporal resolution, its capability to resolve multi-exponential decay functions, and its easy combination with laser scanner ophthalmoscopy, multi-dimensional time-correlated single photon counting was used for fundus imaging. An optimized set up for in vivo lifetime measurements at the human eye-ground will be explained. In this, the fundus fluorescence is excited at 446 or 468 nm and the time-resolved autofluorescence is detected in two spectral ranges between 510 and 560 nm as well as between 560 and 700 nm simultaneously. Exciting the fundus at 446 nm, several fluorescence maxima of lifetime t1 were detected between 100 and 220 ps in lifetime histograms of 40 degrees fundus images. In contrast, excitation at 468 nm results in a single maximum of lifetime t1 = 190 +/- 16 ps. Several fundus layers contribute to the fluorescence intensity in the short-wave emission range 510-560 nm. In contrast, the fluorescence intensity in the long-wave emission range between 560 and 700 nm is dominated by the fluorescence of lipofuscin in the retinal pigment epithelium. Comparing the lateral distribution of parameters of a tri-exponential model function in lifetime images of the fundus with the layered anatomical fundus structure, the shortest component (t1 = 190 ps) originates from the retinal pigment epithelium and the second lifetime (t2 = 1,000 ps) from the neural retina. The lifetime t3 approximately 5.5 ns might be influenced by the long decay of the fluorescence in the crystalline lens. In vitro analysis of the spectral properties of expected fluorophores under the condition of the living eye lightens the interpretation of in vivo measurements. Taking into account the transmission of the ocular media, the excitation of NADH is unlikely at the fundus.

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Section: Introductionmentioning

confidence: 99%

Towards metabolic mapping of the human retina

Schweitzer

Schenke

Hammer

et al. 2007

Microscopy Res & Technique

202

240

View full text Add to dashboard Cite

show abstract

“…This method was tested in an animal model as described by Schweitzer et al [ 18]. In comparison with the results of a hemoxymeter (OSM 2, Radiometer, Copenhagen, Denmark) the oxygen saturation in small arteries and in venules of a neonatal porcine brain was within an error margin of ± 3%.…”

Section: Imaging Spectrometrymentioning

confidence: 99%

“…As spectral and local properties are measured in one step, the oxy gen saturation and the diameter of vessels can be calcu lated on the basis of the imaging spectrum. The cali bration-free measurement of oxygen saturation using imaging spectra was described by Schweitzer et al [18]. The principle of this method is to calculate the extinction spectrum of blood in a first step as the loga…”

Section: Examples For the Application O F Imaging Spectrometry Measurmentioning

confidence: 99%

Imaging Spectrometry in Ophthalmology – Principle and Applications in Microcirculation and in Investigation of Pigments

Schweitzer¹,

Hammer²,

Scibor³

1996

Ophthalmic Res

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Imaging spectrometry is a new technique that permits simultaneous measurements of reflectance spectra at different locations along a line. Results are three-dimensional images, whose coordinates are location, wavelength, and reflectance. A conventional fundus camera is adapted to a spectrograph and an intensified charge coupled device (CCD) matrix detector system. The spectral resolution of this spectrometer is lower than 2 nm within a spectral range between 395 and 710 nm. The local resolution is lower than 23 µm along a line of 1.5 mm. From an imaging spectrum, the extinction spectrum of blood in vessels can be calculated. Also, in case of a noisy extinction spectrum of blood, its approximation by a model function results in calibration-free measurement of the oxygen saturation. Considering the radiation transport in single fundus layers, the local distribution of the concentration-thickness product of xanthophyll, melanin, and choroidal blood can be calculated.

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“…1,2 Hence, this metric is paramount to monitor the onset and progress of DR. Retinal oximeters are, however, still in the research stage of development despite more than 30 yr of work in the field. [3][4][5][6][7] In most systems, a fundus ophthalmoscope is used to illuminate the retina at different wavelengths, since calculations of oxygen saturation rely on the hemoglobin absorbance spectrum. Recently, we developed a multiaperture camera that uses the division of the retinal image obtained with a fundus system into several wavelengthsensitive subimages to compute retinal oxygen saturation.…”

Section: Introductionmentioning

confidence: 99%

Dynamic eye phantom for retinal oximetry measurements

Lemaillet

Ramella‐Roman

2009

J. Biomed. Opt.

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Abstract. Measurements of oxygen saturation and flow in the retina can yield information about eye health and the onset of eye pathologies such as diabetic retinopathy. Recently, we developed a multiaperture camera that uses the division of the retinal image into several wavelength-sensitive subimages to compute retinal oxygen saturation. The calibration of such instruments is particularly difficult due to the layered structure of the eye and the lack of alternative measurement techniques. For this purpose, we realize an in vitro model of the human eye composed of a lens, the retina vessel, and three layers: the choroid, the retinal pigmented epithelium, and the sclera. The retinal vessel is modeled with a microtube connected to a micropump and a hemoglobin reservoir in a closed circulatory system. Hemoglobin oxygenation in the vessel could be altered using a reversible fuel cell. The sclera is represented by a Spectralon slab. The optical properties of the other layers are mimicked using titanium dioxide as a scatterer, ink as an absorber, and epoxy as a supporting structure. The optical thickness of each layer of the eye phantom is matched to each respective eye layer.

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Calibration-free measurement of the oxygen saturation in human retinal vessels

Cited by 33 publications

References 0 publications

Towards metabolic mapping of the human retina

Towards metabolic mapping of the human retina

Imaging Spectrometry in Ophthalmology – Principle and Applications in Microcirculation and in Investigation of Pigments

Dynamic eye phantom for retinal oximetry measurements

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