Quantitative assessment of conjunctival microvascular circulation of the human eye (original) (raw)
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Determination of blood flow velocity in vessels of the bulbar conjunctiva
PRZEGLĄD ELEKTROTECHNICZNY, 2016
The paper presents the methods and the system for registration of digital video recordings of the sclera with a spatial resolution of 2 µm. The pulsed illumination of the sclera was used to eliminate the image blurring caused by the continuous movement of the eyes. At evaluation of blood flow velocity the stabilization of the position of recorded images relatively to the first image frame is used and the trajectory of displacement of the bulbar conjunctiva of the eye is determined. Streszczenie. W artykule omówiono metody oraz opisano system do rejestracji cyfrowych nagrań wideo twardówki z rozdzielczością przestrzenną 2 µm. Zastosowano impulsowe oświetlenie twardówki w celu eliminacji rozmycia obrazu spowodowanego przez ciągły ruch gałek ocznych. Przy ocenie szybkości przepływu krwi przeprowadza się stabilizację pozycji zarejestrowanych obrazów względem pierwszej ramki obrazu oraz wyznacza się trajektorię przemieszczenia spojówki gałki ocznej. (Wyznaczenie szybkości przepływu krwi w naczyniach spojówki gałki ocznej).
British Journal of Ophthalmology, 2002
Aim: To validate the first non-invasive measurements of volumetric ophthalmic artery blood flow in humans. Methods: The ophthalmic arteries of healthy normal adults were examined by Advanced Technology Laboratories (ATL, a subsidiary of Phillips Medical Systems Inc) high definition imaging (HDI) 5000 colour Doppler imaging ultrasound with a 5-12 MHZ probe. A group of 14 subjects for experiment 1 and a group of 10 subjects for experiments 2 and 3 were selected, with the examined eye chosen randomly. Peak systolic velocities (PSV) and end diastolic velocities (EDV) of the ophthalmic artery and central retinal artery were measured and recorded. Cineloops (cinegraphic videos) of the ophthalmic arteries were then recorded with the ATL HDI 5000 and values for ophthalmic artery blood flow were produced offline using experimental analysis software. Multiple regression analysis was used to compare blood flow measurements with PSV and EDV measurements in the ophthalmic artery. In two follow up experiments, intraobserver variation in obtaining cineloops and the interanalyser variability in cineloop analysis were studied. Results: Volumetric flow correlated with ophthalmic artery PSV and EDV (p = 0.02, r 2 = 0.5). There was no correlation with the cental retinal artery. The intraobserver coefficient of variation in obtaining cineloops was 29.89% for blood flow, 19.07% for diameter, and 22.27% for velocity. The coefficients of variation of the measurements of the two cineloop analysers were 40.21% for blood flow, 22.71% for diameter, and 26.34% for velocity. Conclusion: Cineloop analysis produces ophthalmic artery flow measurements which correlate with PSV and EDV, suggesting validity. The intraobserver variation and cineloop analyser variation were found to be in the acceptable range.
Blood velocity pulse quantification in the human conjunctival pre-capillary arterioles
Microvascular Research, 2010
Axial red blood cell velocity pulse was quantified throughout its period by high speed video microcinematography in the human eye. In 30 conjunctival precapillary arterioles (6 to 12 microm in diameter) from 15 healthy humans, axial velocities ranged from 0.4 (the minimum of all the end diastolic values) to 5.84 mm/s (the maximum of all the peak systolic values). With the velocity pulse properly quantified, two parameters can be estimated: (1) the average velocity of the pulse during a cardiac cycle AVV (average velocity value) and (2) the magnitude of the pulsation using Pourcelot's resistive index RI. These parameters are important for the estimation of other hemodynamic parameters such as the average volume flow and the average shear stress. The results of this study revealed that the AVV in the human precapillary arterioles ranged between 0.52 and 3.26 mm/s with a mean value for all microvessels of 1.66 mm/s+/-0.11(SE). The RI ranged between 35.5% and 81.8% with a mean value of 53.1%+/-2.2. Quantitative information was obtained for the first time on the velocity pulse characteristics just before the human capillary bed.
Blood flow in the normal human retina
Investigative Ophthalmology & Visual Science
The laser Doppler technique was used to measure the blood flow rate in 41 major vessels in ten eyes of healthy volunteer subjects. The specific relationship between blood flow rate, F, and vessel diameter, D, was determined for both retinal arteries and retinal veins. On average, F increased with increasing D at a power of 4.1, consistent with the presence of Poiseuille flow. In six eyes of six subjects, measurements on individual vessels were combined to yield the total retinal blood flow rate. The mean and standard deviation of the total retinal blood flow was 80 ± 12 pl/min. The blood flow rate per unit mass of retinal tissue was calculated and found to be in good agreement with that reported for macaque monkeys. Blood flow to the temporal side of the retina was approximately three times larger than to the nasal side. There was no significant difference between blood flow to the superior and the inferior retina. Invest Ophthalmol Vis Sci 30:58-65,1989
Assessment of Conjunctival Microvascular Hemodynamics in Stages of Diabetic Microvasculopathy
Scientific reports, 2017
Diabetes impairs the microcirculation and function of various vital tissues throughout the body. The conjunctival microcirculation can be non-invasively imaged and thus enables assessment of microvascular hemodynamics. In this study, alterations in conjunctival microvascular hemodynamics were quantitatively assessed at stages of increasing diabetic microvasculopathy based on diabetic retinopathy (DR). Subjects were categorized into non-diabetic control (C, N = 34), no clinically visible DR (NDR, N = 47), non-proliferative DR (NPDR, N = 45), and proliferative DR (PDR, N = 35). Conjunctival hemodynamic descriptors, namely vessel diameter (D), blood velocity (V), blood flow (Q), wall shear rate (WSR), and wall shear stress (WSS) were measured in arterioles and venules, and compared between DR and C subjects using generalized linear mixed models. In arterioles, V, WSR, and WSS were lower in NDR (P ≤ 0.01). V was lower in NDR than NPDR and PDR subjects (P ≤ 0.02). In venules, D was highe...
Ocular blood flow measurements in healthy human myopic eyes
Graefe's Archive for Clinical and Experimental Ophthalmology, 2010
Background To evaluate the haemodynamic features of young healthy myopes and emmetropes, in order to ascertain the perfusion profile of human myopia and its relationship with axial length prior to reaching a degenerative state. Methods The retrobulbar, microretinal and pulsatile ocular blood flow (POBF) of one eye of each of twenty-two high myopes (N=22, mean spherical equivalent (MSE) ≤−5.00D), low myopes (N=22, MSE−1.00 to−4.50D) and emmetropes (N=22, MSE±0.50D) was analyzed using color Doppler Imaging, Heidelberg retinal flowmetry and ocular blood flow analyser (OBF) respectively. Intraocular pressure, axial length (AL), systemic blood pressure, and body mass index were measured.