Imaging Single–Cell Blood Flow in the Smallest to Largest Vessels in the Living Retina

Impact StatementUsing a specialized camera that corrects for eye blur, millions of single blood cells are imaged and their speed measured, as they travel through the largest-to-smallest vessels of the retina.AbstractTissue light scatter limits the visualization of the microvascular network deep inside the living mammal. The transparency of the mammalian eye provides a noninvasive view of the microvessels of the retina, a part of the central nervous system. Despite its clarity, imperfections in the optics of the eye blur microscopic retinal capillaries, and single blood cells flowing within. This limits early evaluation of microvascular diseases that originate in capillaries. To break this barrier, we use adaptive optics to noninvasively measure single–cell blood flow, in one of the most widely used research animals: the C57BL/6J mouse. Flow ranged four orders of magnitude (0.0002–1.55 µL min−1) across the full spectrum of retinal vessel diameters (3.2–45.8 µm), without requiring surgery or contrast dye. Here we describe the data collection approach using adaptive optics and provide an analysis pipeline that can measure millions of blood cell speeds automatically.

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Imaging single-cell blood flow in the smallest to largest vessels in the living retina

eLife ◽

10.7554/elife.45077 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 18

Author(s):

Aby Joseph ◽

Andres Guevara-Torres ◽

Jesse Schallek

Keyword(s):

Blood Flow ◽

Single Cell ◽

Adaptive Optics ◽

Retinal Vessel ◽

Full Spectrum ◽

Early Evaluation ◽

Ultrafast Imaging ◽

Adaptive Optics Imaging ◽

The Central Nervous System ◽

Measured Flow

Tissue light scatter limits the visualization of the microvascular network deep inside the living mammal. The transparency of the mammalian eye provides a noninvasive view of the microvessels of the retina, a part of the central nervous system. Despite its clarity, imperfections in the optics of the eye blur microscopic retinal capillaries, and single blood cells flowing within. This limits early evaluation of microvascular diseases that originate in capillaries. To break this barrier, we use 15 kHz adaptive optics imaging to noninvasively measure single-cell blood flow, in one of the most widely used research animals: the C57BL/6J mouse. Measured flow ranged four orders of magnitude (0.0002–1.55 µL min–1) across the full spectrum of retinal vessel diameters (3.2–45.8 µm), without requiring surgery or contrast dye. Here, we describe the ultrafast imaging, analysis pipeline and automated measurement of millions of blood cell speeds.

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Arteriolar Oxygen Saturation, Cerebral Blood Flow, and Retinal Vessel Diameters

Ophthalmology ◽

10.1016/j.ophtha.2007.06.036 ◽

2008 ◽

Vol 115 (5) ◽

pp. 887-892 ◽

Cited By ~ 38

Author(s):

Frank Jan de Jong ◽

Meike W. Vernooij ◽

M. Kamran Ikram ◽

M. Arfan Ikram ◽

Albert Hofman ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Oxygen Saturation ◽

Retinal Vessel ◽

Retinal Vessel Diameters

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ETa-receptor blockade, but not ACE inhibition, blunts retinal vessel response during isometric exercise

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00947.2005 ◽

2006 ◽

Vol 290 (4) ◽

pp. H1693-H1698 ◽

Cited By ~ 9

Author(s):

Alexandra Luksch ◽

Barbara Wimpissinger ◽

Kaija Polak ◽

Kerstin Jandrasits ◽

Leopold Schmetterer

Keyword(s):

Blood Flow ◽

Intraocular Pressure ◽

Angiotensin Ii ◽

Isometric Exercise ◽

Retinal Vessel ◽

Flow Regulation ◽

Retinal Blood Flow ◽

Receptor Blockade ◽

Converting Enzyme ◽

Retinal Vessel Diameters

Angiotensin II and endothelin-1 are potent vasoconstrictors that appear to play a role in retinal blood flow regulation. In the present study, we investigated the possible role of the angiotensin and the endothelin system in the regulation of retinal vessel diameters during isometric exercise in healthy humans. The study design was randomized, double-masked, placebo-controlled, and three-way cross over. Twelve healthy subjects performed squatting exercises for 6 min during infusion of either an angiotensin-converting enzyme inhibitor (enalapril), an ETA-receptor antagonist (BQ-123), or placebo. Retinal vessel diameters were measured continuously with the Zeiss retinal vessel analyzer. Systemic hemodynamics were assessed noninvasively, and intraocular pressure was measured with applanation tonometry. Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a vasoconstriction in retinal arteries and veins. Intraocular pressure was only slightly increased during the squatting periods. BQ-123 significantly blunted the exercise-induced decrease in venous ( P < 0.01) and arterial ( P < 0.02, ANOVA) vessel diameters but had no effect on basal retinal diameters. By contrast, enalapril did neither influence vessel diameter at baseline conditions nor in response to isometric exercise. The data of the present study indicate that retinal vasoconstriction during isometric exercise is modified by ETA-receptor blockade, whereas it is not altered by angiotensin-converting enzyme inhibition. Hence, the present data indicate that endothelin-1, but not angiotensin II, is involved in retinal blood flow regulation during isometric exercise.

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Effect of Increased Oxygen Tension on Flicker-Induced Vasodilatation in the Human Retina

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2014.161 ◽

2014 ◽

Vol 34 (12) ◽

pp. 1914-1918 ◽

Cited By ~ 11

Author(s):

Stefan Palkovits ◽

Reinhard Told ◽

Agnes Boltz ◽

Doreen Schmidl ◽

Alina Popa Cherecheanu ◽

...

Keyword(s):

Blood Flow ◽

Oxygen Tension ◽

Neural Activity ◽

Retinal Vessel ◽

Human Retina ◽

Flicker Response ◽

Tightly Coupled ◽

Hyperemic Response ◽

Retinal Vessel Diameters ◽

Stimulation Of

In the retina, blood flow and neural activity are tightly coupled. Stimulation of the retina with flickering light is accompanied by an increase in blood flow. The current study seeks to investigate whether an increase in oxygen tension modulates flicker (FL)-induced vasodilatation in the human retina. A total of 52 healthy volunteers were included. Via a breathing mask, 100% oxygen (O2) was administered in one, a mixture of 8% carbon dioxide and 92% oxygen (C/O) in a second cohort. Retinal vessel diameters were measured with a Vessel Analyzer and FL responses were assessed before and during the breathing periods. At baseline, FL stimulation increased retinal vessel diameters by +3.7 ± 2.3% in arteries and by +5.1 ± 3.7% in veins. Breathing of C/O led to a decrease in arterial (−9.0 ±,6.9%) and venous (−11.3 ± 5.9%) vessel calibers. Flicker response was increased to 5.7 ± 2.5% in arteries and to 8.6 ± 4.1% in veins. Breathing of pure O2 induced a vasoconstriction of vessel diameters by −14.0 ± 5.3% in arteries and −18.4 ± 7.0% in veins and increased FL responses in arteries (+6.2 ± 2.8%) and veins (+7.2 ± 3.1%). Systemic hyperoxia increases FL-induced retinal vasodilatation in the retina. The mechanism by which oxygen modulates the hyperemic response to FL stimulation remains to be elucidated.

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Mathematical Models for Some Aspects of Blood Microcirculation

Symmetry ◽

10.3390/sym13061020 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1020

Author(s):

Angiolo Farina ◽

Antonio Fasano ◽

Fabio Rosso

Keyword(s):

Blood Flow ◽

Mathematical Models ◽

Red Blood Cells ◽

Blood Cells ◽

Blood Rheology ◽

Small Class ◽

Small Vessels ◽

Blood Microcirculation ◽

Peculiar Behavior

Blood rheology is a challenging subject owing to the fact that blood is a mixture of a fluid (plasma) and of cells, among which red blood cells make about 50% of the total volume. It is precisely this circumstance that originates the peculiar behavior of blood flow in small vessels (i.e., roughly speaking, vessel with a diameter less than half a millimeter). In this class we find arteriolas, venules, and capillaries. The phenomena taking place in microcirculation are very important in supporting life. Everybody knows the importance of blood filtration in kidneys, but other phenomena, of not less importance, are known only to a small class of physicians. Overviewing such subjects reveals the fascinating complexity of microcirculation.

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In Vitro Assay for Single-cell Characterization of Impaired Deformability in Red Blood Cells under Recurrent Episodes of Hypoxia

Lab on a Chip ◽

10.1039/d1lc00598g ◽

2021 ◽

Author(s):

YUHAO QIANG ◽

Jia Liu ◽

Ming Dao ◽

E Du

Keyword(s):

Shear Stress ◽

Red Blood Cells ◽

Single Cell ◽

Blood Cells ◽

Blood Circulation ◽

In Vitro Assay ◽

Vitro Assay ◽

Cyclic Shear

Red blood cells (RBCs) are subjected to recurrent changes in shear stress and oxygen tension during blood circulation. The cyclic shear stress has been identified as an important factor that...

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Association of changes of retinal vessels diameter with ocular blood flow in eyes with diabetic retinopathy

Scientific Reports ◽

10.1038/s41598-021-84067-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yoshitaka Ueno ◽

Takeshi Iwase ◽

Kensuke Goto ◽

Ryo Tomita ◽

Eimei Ra ◽

...

Keyword(s):

Blood Flow ◽

Diabetic Retinopathy ◽

Adaptive Optics ◽

Laser Speckle ◽

The Other ◽

Systemic Hypertension ◽

Laser Speckle Flowgraphy ◽

Retinal Vessels ◽

External Diameter ◽

The Mean

AbstractWe investigated morphological changes of retinal arteries to determine their association with the blood flow and systemic variables in type 2 diabetes patients. The patients included 47 non-diabetic retinopathy eyes, 36 mild or moderate nonproliferative diabetic retinopathy (M-NPDR) eyes, 22 severe NPDR (S-NPDR) eyes, 32 PDR eyes, and 24 normal eyes as controls. The mean wall to lumen ratio (WLR) measured by adaptive optics camera was significantly higher in the PDR groups than in all of the other groups (all P < 0.001). However, the external diameter of the retinal vessels was not significantly different among the groups. The mean blur rate (MBR)-vessel determined by laser speckle flowgraphy was significantly lower in the PDR group than in the other groups (P < 0.001). The WLR was correlated with MBR-vessel (r = − 0.337, P < 0.001), duration of disease (r = 0.191, P = 0.042), stage of DM (r = 0.643, P < 0.001), systolic blood pressure (r = 0.166, P < 0.037), and presence of systemic hypertension (r = 0.443, P < 0.001). Multiple regression analysis demonstrated that MBR-vessel (β = − 0.389, P < 0.001), presence of systemic hypertension (β = 0.334, P = 0.001), and LDL (β = 0.199, P = 0.045) were independent factors significantly associated with the WLR. The increased retinal vessel wall thickness led to a narrowing of lumen diameter and a decrease in the blood flow in the PDR group.

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