Bidirectional LDV system for absolute measurement of blood speed in retinal vessels

Riva, Charles E.; Feke, Gilbert T.; Eberli, Bruno; Benary, V.

doi:10.1364/ao.18.002301

Cited by 113 publications

(48 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Light scattered from stationary tissue is not shifted and acts as the reference frequency from which a relative change in retinal blood velocity is measured (16). With the use of two photomultipliers separated by a known angle, the maximum frequency shift is subtracted to allow the absolute quantification of centerline blood velocity irrespective of the angle between the moving particle and the reflected beam (15,41). A red diode laser (675 nm, 80 ϫ 50-m oval) is used to measure velocity every 0.02 s across a 2-s measurement window, which results in a velocity-time trace.…”

Section: Methodsmentioning

confidence: 99%

“…Magnification effects associated with refractive and axial components of ametropia are corrected to provide absolute measurements of diameter (in m), velocity (in mm/s), and flow (in l/min). The technological principles used in this device have been described in detail elsewhere (3,15,30,41). In addition, this device has been extensively evaluated on clinically normal subjects (19,23) and those with various types of retinal pathologies (30,54).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Gilmore¹,

Hudson²,

Preiss³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

Fisher. Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation. Am J Physiol Heart Circ Physiol 288: H2912-H2917, 2005. First published February 11, 2005 doi:10.1152/ajpheart.01037.2004.-The aim of this study was to simultaneously quantify the magnitude and response characteristics of retinal arteriolar diameter and blood velocity induced by an isocapnic hyperoxic provocation in a group of clinically normal subjects. The sample comprised 10 subjects (mean age, 25 yr; range, 21-40 yr). Subjects initially breathed air for 5-10 min, then breathed O 2 for 20 min, and then air for a final 10-min period via a sequential rebreathing circuit (Hi-Ox; Viasys) to maintain isocapnia. Retinal arteriolar diameter and blood velocity measurements were simultaneously acquired with a Canon laser blood flowmeter (CLBF-100). The response magnitude, time, and lag of diameter and velocity were calculated. In response to hyperoxic provocation, retinal diameter was reduced from control values of 111.6 (SD 13.1) to 99.8 (SD 10.6; P Ͻ 0.001) m and recovered after withdrawal of hyperoxia. Retinal blood velocity and flow concomitantly declined from control values of 32.2 (SD 6.4) mm/s and 9.4 (SD 2.5) l/min to 20.7 (SD 3.4) mm/s and 5.1 (SD 1.3) l/min, respectively (P Ͻ 0.001 for both velocity and flow), and recovered after withdrawal of hyperoxia. The response times and response lags were not significantly different for each parameter between effect and recovery or between diameter and velocity. We conclude that arteriolar retinal vascular reactivity to hyperoxic provocation is rapid with a maximal vasoconstrictive effect occurring within a maximum of 4 min. Although there was a trend for diameter to respond before velocity to the isocapnic hyperoxic provocation, the response characteristics were not significantly different between diameter and velocity. vascular reactivity; laser Doppler velocimetry; isocapnic hyperoxia THE BLOOD SUPPLY TO THE INNER retina is derived from the central retinal artery, whereas the choriocapillaris supplies the outer retina and photoreceptors. The retinal tissue is one of the most metabolically active in the body and, correspondingly, an uninterrupted nutrient supply is essential (50). The inner retinal blood vessels (i.e., past the lamina cribrosa) are thought to be unique due to the absence of an autonomic nerve supply to regulate vascular tone (53). Blood supply to the inner retina is regulated via local feedback signals that alter retinal perfusion in response to changes in systemic blood pressure or the concentration of certain metabolites (11,18). In particular, retinal blood flow is strongly dependent on the partial pressure of oxygen (PO 2 ; Refs. 14,25,31,42,48).The retinal vasculature can be noninvasively visualized and, consequently, its hemodynamic parameters quantified. Impairment of vascular reactivity has been demonstrated in the pathogenesis of various ocular diseases including diabetic retinopathy (13,20,25,32). Administration of O 2 has p...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Gilmore¹,

Hudson²,

Preiss³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

show abstract

“…The principle underlying the CLBF is that of bidirectional laser Doppler velocimetry. By utilizing two photo multipliers separated by a known angle, the CLBF provides an absolute, pointwise measurement of centerline blood velocity (25,26). A measurement window of 2 s permits continuous velocity readings, and a plot of velocity versus time is acquired.…”

mentioning

confidence: 99%

Retinal Hemodynamics in Early Diabetic Macular Edema

et al. 2006

View full text Add to dashboard Cite

The objective of this study was to establish the baseline retinal hemodynamic characteristics of stratified groups of diabetic patients at increasing risk for the development of diabetic macular edema (DME). Group 1 had 50 control subjects, group 2 had 56 diabetic patients without clinically visible retinopathy, group 3 had 54 diabetic patients with microaneurysms and/or hard exudates within two disc diameters of the fovea in the absence of clinically manifest DME, and group 4 had 40 patients with clinically manifest DME. Retinal hemodynamics (diameter, velocity, maximum-to-minimum velocity ratio, and flow) were assessed. Intraocular pressure, blood pressure, and relevant systemic markers of diabetes control and complications were also undertaken. The maximum-to-minimum velocity ratio was elevated with increasing risk of clinically significant DME (P < 0.0001). No significant differences were found between the groups with respect to diameter, velocity, or flow. The maximum-to-minimum velocity ratio was correlated to age, duration of diabetes, blood pressure, pulse rate, intraocular pressure, and serum potassium levels. In conclusion, the maximum-to-minimum velocity ratio was significantly increased with increasing risk of development of DME. Retinal arteriolar hemodynamics were positively correlated to age, duration of diabetes, and blood pressure. These findings suggest a reduction in the compliance (i.e., an increase of vascular rigidity) of the arteriolar circulation with increasing risk of DME. Diabetes 55:813-818, 2006

show abstract

“…The measurement is independent of the direction of the incident light defined by K in (fig. 2) [43,44]. Combined with D measurements of these vessels mean BF is calculated as π × D 2 × V mean /4.…”

Section: Noninvasive Techniques Used In Physiological and Clinical Rementioning

confidence: 99%

Retinal Blood Flow Evaluation

Pournaras

Riva

2012

Ophthalmologica

Self Cite

View full text Add to dashboard Cite

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 techniques that measure the velocities of blood in discrete areas of the retinal tissue microcirculation. Adding a scanning capability, a spatial map of velocities across the retinal tissue is obtained. The blue-field simulation technique allows the quantification of the velocity, number and velocity pulsatility of leukocytes moving in the retinal capillaries of the macular region. With color Doppler imaging, the peak systolic and end-diastolic values of blood velocity in the ophthalmic and central retinal artery are measured, from which a resistivity index is obtained. These techniques may help better understand the role of altered retinal blood flow and its regulation in the pathogenesis of retinal diseases of vascular origin.

show abstract

Bidirectional LDV system for absolute measurement of blood speed in retinal vessels

Cited by 113 publications

References 5 publications

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Retinal Hemodynamics in Early Diabetic Macular Edema

Retinal Blood Flow Evaluation

Contact Info

Product

Resources

About