A laser Doppler velocimetry study of the effect of hypoglycaemia on retinal blood flow in the minipig (original) (raw)
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Retinal blood flow during hyperglycemia. A laser Doppler velocimetry study
Investigative Ophthalmology & Visual Science
The effect of different rates of glucose infusion on the retinal circulation was studied in Gottingen breed minipigs. Seven minipigs were made hyperglycemic rapidly with an intravenous bolus injection of 50% dextrose, after which a slow dextrose infusion maintained hyperglycemia for 60 minutes. Seven minipigs were more gradually made hyperglycemic over 60 minutes with a slow intravenous infusion of 50% dextrose, and a further seven had a control infusion of urea of equal volume and osmolality over 60 minutes. Retinal blood flow (RBF) was determined from the maximum (centerline) velocity of the blood (Vmax) (determined by bidirectional laser doppler velocimetry) and the vessel diameter (D) (determined from monochromatic fundus photographs). Measurements were made in a single temporal retinal vein of each animal at baseline, during, and after each of the infusions. Plasma glucose rose from 6.1 ± 0.5-25.3 ± 1 . 5 mM (mean ± standard error) during the bolus infusion and from 6.4 ± 0.7-22.0 ± 0.7 mM during the slow infusion. The bolus and the slow glucose infusions both produced large increases in RBF (63% and 62%, respectively) which were mainly attributable to increases in V max . The urea infusion had no significant effect on RBF, V max , or D. The ocular perfusion pressure rose slowly and was significantly elevated after 60 minutes of slow glucose infusion but not after the urea infusion.
Retinal hemodynamics in proliferative diabetic retinopathy. A laser Doppler velocimetry study
Investigative ophthalmology & visual science, 1993
This study investigated retinal hemodynamic changes associated with different pathologic features observed on fundus color and fluorescein angiography in patients with proliferative diabetic retinopathy. Retinal circulatory characteristics were investigated in 25 eyes of 23 diabetic patients with proliferative retinopathy using a combination of bidirectional laser Doppler velocimetry and monochromatic fundus photography. Eyes with severe capillary nonperfusion had 32% less average volumetric blood flow rate (Q) than eyes with less severe nonperfusion (P = 0.0005). In addition, eyes with severe vessel staining with fluorescein had 20% less average Q than eyes without staining (P = 0.0508). Eyes with severe fluorescein leakage in the macula had a 17% larger total venous cross-section than eyes with milder leakage (P = 0.027). Eyes with clinically significant macular edema had 11% larger average venous diameter than eyes without this feature (P = 0.0085). Severe capillary nonperfusion ...
Retinal haemodynamics in individuals with well-controlled type 1 diabetes
Diabetologia, 2008
Aims/hypothesis Abnormalities in retinal haemodynamics have been reported in patients with type 1 diabetes in advance of clinical retinopathy. These abnormalities could therefore be useful as early markers or surrogate endpoints for studying the microangiopathy. Since the DCCT, the increased focus on good glycaemic control is changing the natural history of diabetic retinopathy. Based on this, the aim of this study was to investigate whether patients with type 1 diabetes treated entirely or mostly in the post-DCCT era and tested in the absence of confounding factors show retinal haemodynamic abnormalities. Methods We measured retinal haemodynamics by laser Doppler flowmetry in 33 type 1 diabetic individuals with no or minimal retinopathy (age 30±7 years, duration of diabetes 8.8±4.6 years, 9% showing microaneurysms), and 31 age-and sex-matched non-diabetic controls. The study Diabetologia (
Ophthalmologica, 2013
Much of our basic knowledge of retinal blood flow regulation is based on data obtained from animal experiments through the use of invasive techniques. However, during the last decades, major developments in the field of optics and lasers have led to a variety of noninvasive techniques, which have been applied to the human eye for the investigation of retinal hemodynamics, and more specifically the regulation of retinal blood flow in response to a number of physiological and pharmacological stimuli. The Retinal Vessel Analyzer has markedly simplified the measurement of the diameter of retinal vessels, as well as the change in this diameter evoked by various physiological stimuli (dynamic measurements). Bidirectional laser Doppler velocimetry allows the measurement of absolute red blood cell centerline velocity, which, when combined with the diameter allows the calculation of retinal blood flow in the main retinal vessels. Laser Doppler flowmetry and laser speckle flowgraphy are techn...
PLOS ONE, 2015
Noninvasive techniques for ocular blood perfusion assessment are of crucial importance for exploring microvascular alterations related to systemic and ocular diseases. However, few techniques adapted to rodents are available and most are invasive or not specifically focused on the optic nerve head (ONH), choroid or retinal circulation. Here we present the results obtained with a new rodent-adapted compact fundus camera based on laser Doppler flowmetry (LDF). Methods A confocal miniature flowmeter was fixed to a specially designed 3D rotating mechanical arm and adjusted on a rodent stereotaxic table in order to accurately point the laser beam at the retinal region of interest. The linearity of the LDF measurements was assessed using a rotating Teflon wheel and a flow of microspheres in a glass capillary. In vivo reproducibility was assessed in Wistar rats with repeated measurements (inter-session and inter-day) of retinal arteries and ONH blood velocity in six and ten rats, respectively. These parameters were also recorded during an acute intraocular pressure increase to 150 mmHg and after heart arrest (n = 5 rats). Results The perfusion measurements showed perfect linearity between LDF velocity and Teflon wheel or microsphere speed. Intraclass correlation coefficients for retinal arteries and ONH velocity (0.82 and 0.86, respectively) indicated strong inter-session repeatability and stability. Inter-day reproducibility was good (0.79 and 0.7, respectively). Upon ocular blood flow cessation, the retinal artery velocity signal substantially decreased, whereas the ONH
International Journal of Contemporary Medicine, Surgery and Radiology, 2019
Estimation of orbital blood flow velocity from Doppler of the CRA and PCA could yield promising results when used in the identification of early retinopathy in diabetics. The aim of this study is to measure the blood flow parameters in CRA and PCA of the eye with Doppler in diabetes and to compare with controls. Material and methods: Doppler was performed 200 individuals (100 diabetics and 100 controls) in a randomized blinded format. The peak systolic velocity (PSV), end diastolic velocity (EDV), resistance index (RI) of the CRA and the PCA were measured in both groups. Dilated fundoscopy was done for the diabetics for correlation. The data was analyzed using ANOVA and student T test ("p" value < 0.05) Results: As compared with the controls, both the CRA and PCA in diabetics have slower velocities and significantly higher RI. In the CRA of diabetics there was a statistically significant decrease in both the PSV and EDV as compared to the controls. The RI of the CRA was increased in diabetics as compared to the controls. Similarly, there was a decrease in both the PSV and EDV of the PCA in diabetics compared to the control group. The RI of PCA was significantly increased in diabetics as compared to the controls. Conclusion: Significant changes in retrobulbar blood flow are found in eyes with diabetic retinopathy which can be detected by colour Doppler and it could serve as a promising modality to assess hemodynamic changes in different stages of diabetic retinopathy.
Assessment of retinal and choroidal blood flow changes using laser Doppler flowmetry in rats
Current eye research, 2013
A new noninvasive laser Doppler flowmetry (LDF) probe (one emitting fiber surrounded by a ring of eight collecting fibers, 1-mm interaxis distance) was tested for its sensitivity to assess the retinal/choroidal blood flow variations in response to hypercapnia, hyperoxia, diverse vasoactive agents and following retinal arteries photocoagulation in the rat. After pupil dilation, a LDF probe was placed in contact to the cornea of anesthetized rats in the optic axis. Hypercapnia and hyperoxia were induced by inhalation of CO(2) (8% in medical air) and O(2) (100%) while pharmacological agents were injected intravitreously. The relative contribution of the choroidal circulation to the LDF signal was estimated after retinal artery occlusion by photocoagulation. Blood flow was significantly increased by hypercapnia (18%), adenosine (14%) and sodium nitroprusside (16%) as compared to baseline values while it was decreased by hyperoxia (-8%) and endothelin-1 (-11%). Photocoagulation of retina...
Scanning laser Doppler flowmeter study of retinal blood flow in macular area of healthy volunteers
Aim: To compare the interocular and intraocular differences of capillary perfusion, and the intraocular regional differences of retinal blood flow in the macular area of healthy volunteers. Methods: Tissue blood flow in the macula was examined in both eyes of 20 healthy volunteers with the Heidelberg retinal flowmeter. Blood flow measurements were made in a 10˚62.5˚area superior and inferior to the macula. The mean blood flow (MBF) was calculated by an automatic full field perfusion image analyser program. The MBF in the right and left eyes and in the superior and inferior macular areas of the same eye were compared. Results: The ratios of the MBF in the right eye to the left eye in the macular areas were 1.00, and 1.03, respectively. The ratio of the MBF in the superior macular area to the inferior area was 1.01 for the right eyes and 1.04 for the left eyes. Conclusions: Because no significant differences were found in the MBF between the two eyes and between the superior and inferior macular areas in the same eye, interocular (for example, affected eye versus fellow eye) and intraocular (superior versus inferior macular areas) comparisons of MBF can be made to determine if changes in retinal perfusion have occurred.
Ocular blood flow assessment using continuous laser Doppler flowmetry
Acta Ophthalmologica, 2009
Acta Ophthalmol. 2010: 88: 622–629Acta Ophthalmol. 2010: 88: 622–629Abstract.This article describes the technique of continuous laser Doppler flowmetry (LDF) as applied to the measurement of the flux of red blood cells in the optic nerve head, iris and subfoveal choroid. Starting with the exposition of the physical principles underlying LDF, we first describe the various devices developed to perform LDF in these vascular beds. We then discuss the clinical protocols, blood flow parameters, calibration procedures, reproducibility and limitations of the LDF technique. Various problems still need to be solved in order to bring to light the full potential of LDF in the assessment of microcirculatory haemodynamics.This article describes the technique of continuous laser Doppler flowmetry (LDF) as applied to the measurement of the flux of red blood cells in the optic nerve head, iris and subfoveal choroid. Starting with the exposition of the physical principles underlying LDF, we first describe the various devices developed to perform LDF in these vascular beds. We then discuss the clinical protocols, blood flow parameters, calibration procedures, reproducibility and limitations of the LDF technique. Various problems still need to be solved in order to bring to light the full potential of LDF in the assessment of microcirculatory haemodynamics.