Fundus camera based retinal LDV

Riva, Charles E.; Grunwald, Juan E.; Sinclair, Stephen H.; O’Keefe, Kevin J.

doi:10.1364/ao.20.000117

Cited by 114 publications

(54 citation statements)

References 3 publications

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“…Retinal blood flow studies Riva, Grunwald, Sinclair & O'Keefe (1981) and Sullivan, Davis & Kohner (1990). The data collected were stored on the hard disk of the computer and were analysed later in a randomized masked fashion.…”

Section: Methodsmentioning

confidence: 99%

The effect of experimental hypertension on retinal vascular autoregulation in humans: a mechanism for the progression of diabetic retinopathy

Rassam

Patel²,

Kohner³

1995

Experimental Physiology

137

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SUMMARYSince the retinal vessels have no sympathetic innervation, blood flow in response to raised blood pressure is dependent on autoregulation. To determine the effect of hypertension on retinal haemodynamics and the autoregulatory capacity of the retinal circulation under conditions of normoglycaemia and hyperglycaemia, retinal blood flow was measured before and after raising the systemic blood pressure in ten normal control subjects, ten diabetic subjects with blood glucose < 10 mmol 11 and ten diabetic subjects with blood glucose > 15 mmol 1-'. A controlled nse in systemic blood pressure was achieved using an intravenous infusion of tyramine. Retinal volume flow was determined from red cell velocity using laser Doppler velocimetry and from retinal vessel diameter measurements using digital image analysis of fundus photographs. With a 40 % increase in mean arterial blood pressure (MAP), there was a significant increase in retinal blood flow of 32.9 + 7-1 % in non-diabetic controls. In diabetics at the low blood glucose level, the increase in retinal blood flow was significant at 30% increase in MAP (23.6 + 87 %, P = 0-032) and at 40 % increase (49-9 + 12-03 %, P = 0-004). Diabetics with high blood glucose failed to autoregulate at any of the increased levels of MAP (15 % increase, 27 0 + 11 1 %; 30 % increase, 66.9 + 19.8 %; and 40 % increase, 101 9 + 21 4 %; P < 0.022). The coefficients of autoregulation showed that in non-diabetic controls, retinal vascular autoregulation broke down with increases in MAP of between 30 and 40 %. In diabetic subjects, it broke down between 15 and 30 % in normoglycaemia and at less than 15 % in hyperglycaemia. This study demonstrates an impairment in retinal vascular autoregulation in response to raised systemic blood pressure in diabetic subjects, more so at an elevated blood glucose level, thus providing a mechanism for the detrimental effect of hypertension on diabetic retinopathy.

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Section: Methodsmentioning

confidence: 99%

The effect of experimental hypertension on retinal vascular autoregulation in humans: a mechanism for the progression of diabetic retinopathy

Rassam

Patel²,

Kohner³

1995

Experimental Physiology

137

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“…Feke and Riva [1] were the first to describe this technique in 1978 [2]. Subsequently, each one developed a bidirectional laser Doppler velocimetry (BLDV) system of their own, differing significantly in optical configuration and modes of data analysis [3,4]. Riva et al [5] and Feke et al [6] published their results on retinal blood flow velocities and rates among normal volunteers in 1985 and 1989, respectively.…”

Section: Introductionmentioning

confidence: 99%

Retinal Blood Flow in the Normal Human Eye Using the Canon Laser Blood Flowmeter

Garcia

Rosen³

2002

Ophthalmic Res

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Purpose: To establish a retinal blood flow database in normal human eyes using the Canon Laser Blood Flowmeter (CLBF). Method: Fourteen healthy subjects (7 males, 7 females) between the ages of 24 and 33 underwent birectional laser Doppler velocimetry (BLDV) in one eye using the CLBF. Measurements consisting of blood vessel diameter (D) in micrometers, velocity (V) in millimeters per second, and flow (F) in microliters per minute were recorded at sites along the major retinal veins. Four to six veins were measured in each eye. Total volumetric blood flow was calculated as the sum of the venous flow rates in the major veins. Results: Total retinal blood flow could be reliably determined on 5 of the subjects (1 male, 4 females). Venous blood vessel diameter ranged from 84 to 177 µm. The correlations between D and F, as well as D and V were found to be significant. Specifically, the correlation coefficient between D and F was 0.885 (p ≤ 0.001), while the log-log regression coefficient was 3.35 ± 0.23 (p ≤ 0.001). The correlation coefficient between D and V was 0.694 (p ≤ 0.001), while the log-log regression coefficient was 1.43 ± 0.27 (p ≤ 0.001). Total venous blood flow showed a mean of 64.9 ± (SD) 12.8 µl/min (range: 50.9–80.6 µl/min). Venous blood flow averaged 44.1 ± 4.5 µl/min temporally and 20.8 ± 9.2 µl/min nasally, showing a temporal retinal blood flow approximately twice that of the nasal retina (p < 0.001). On the other hand, venous blood flow averaged 30.6 ± 9.8 µl/min superiorly and 34.3 ± 8.0 µl/min inferiorly. These values showed no statistical difference. Conclusion: The average total retinal blood flow in 5 healthy subjects using the CLBF was 64.9 ± 12.8 µl/min. Venous blood flow at the temporal retina was about twice that of the nasal retina, whereas flow at the superior and inferior retina showed no statistical difference. Our findings are comparable with studies done using a different BLDV system.

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“…2) [42]. Retinal BF (in µl/min) in the main retinal vessels is calculated from the centerline velocity (V max ) of RBCs [43]. The measurement is independent of the direction of the incident light defined by K in (fig.…”

Section: Noninvasive Techniques Used In Physiological and Clinical Rementioning

confidence: 99%

“…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

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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.

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Fundus camera based retinal LDV

Cited by 114 publications

References 3 publications

The effect of experimental hypertension on retinal vascular autoregulation in humans: a mechanism for the progression of diabetic retinopathy

The effect of experimental hypertension on retinal vascular autoregulation in humans: a mechanism for the progression of diabetic retinopathy

Retinal Blood Flow in the Normal Human Eye Using the Canon Laser Blood Flowmeter

Retinal Blood Flow Evaluation

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