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Martial Geise - One of the best experts on this subject based on the ideXlab platform.
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compact laser Doppler Flowmeter ldf fundus camera for the assessment of retinal blood perfusion in small animals
PLOS ONE, 2015Co-Authors: Marielle Mentek, Frederic Truffe, Christophe Chique, Diane Godinribuo, Serge Amoos, Corinne Loeuille, Mario Ernabei, Martial GeiseAbstract:Purpose 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 signal did not significantly vary, suggesting that it could mostly be attributed to tissue light scattering. Conclusion We have demonstrated that, while not adapted for ONH blood perfusion assessment, this device allows pertinent, stable and repeatable measurements of retinal blood perfusion in rats.
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schlieren laser Doppler Flowmeter for the human optical nerve head with the flicker stimuli
Journal of Biomedical Optics, 2013Co-Authors: Martial Geise, Frederic Truffe, Hugo Evequoz, Hafid Khayi, Enjami Motte, Christophe ChiqueAbstract:We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the Flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination point. LDF measurements are based on heterodyne detection of Doppler shifted back-scattered light. We also describe an automated analysis of the LDF signals which rejects artifacts and false signals such as blinks. By using a Doppler simulator consisting of a lens and a rotating diffusing wheel, we demonstrate that velocity and flow vary linearly with the speed of the wheel. A cohort of 12 healthy subjects demonstrated that flicker stimulation induces an increase of 17.8% of blood flow in the ONH.
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choroidal laser Doppler Flowmeter with enhanced sensitivity based on a scattering plate
Journal of Biomedical Optics, 2011Co-Authors: Chua Wang, Zhihua Ding, Martial Geise, Minghui CheAbstract:A portable choroidal laser Doppler Flowmeter (LDF) with enhanced sensitivity based on a scattering plate is developed. The portable LDF is weighted 2 kg operated at center wavelength of 780 nm, leading to a better penetration into the eye fundus in contrast to the previous LDF operated at center wavelength of 670 nm. Enhancement of number of detected photons that undergo Doppler scattering and improved measured speed of choroidal blood flow are achieved with the use of a scattering plate positioned in front of the eye. The mechanism of detection and sensitivity enhancement is theoretically analyzed. Evaluation of system performance is done by in vivo measurements on ten volunteers. The results demonstrate that an increased percentage of backscattering light at high Doppler shift frequency is collected due to utilization of the scattering plate. However, this kind of light detection influences spatial resolution of the system and decreases the total signal measured. The proposed method for detection and sensitivity enhancement might be useful in a case where the perception of very slight alternation of blood flow is pursued and the spatial resolution is not as critical as that in a choroidal vascular bed.
Akio Sakai - One of the best experts on this subject based on the ideXlab platform.
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evaluation of the use of an integration type laser Doppler Flowmeter with a temperature loading instrument for measuring skin blood flow in elderly subjects during cooling load comparison with younger subjects
International Journal of Biometeorology, 2003Co-Authors: Yoshinao Nagashima, Yukihiro Yada, Toshiyuki Suzuki, Akio SakaiAbstract:An integration-type laser-Doppler Flowmeter, equipped with a temperature-load instrument, for measuring skin blood flow (ILD-T), and analytical parameters developed in a previous study were used to compare changes in the skin blood flow in the forehead and cheek in elderly subjects (in their 60s and 70s) with those in younger subjects (in their teens to 50s). Age-related differences in skin blood flow in the forehead and cheek in response to cooling were evaluated in 90 healthy women in their teens to 70s (mean age: 17.2 ± 0.33 years for teenagers; 24.3 ± 0.76 years for those aged 20–29 years; 34.8 ± 1.12 years for those aged 30–39 years; 43.3 ± 0.78 years for those aged 40–49 years; 53.8 ± 1.13 years for those aged 50–59 years; 63.5 ± 0.55 years for those aged 60–69 years; 72.2 ± 0.70 years for those aged 70–79 years). The measurement was performed continuously for 5 min: for 1 min at a sensor temperature of 30 °C, for 2 min after the setting of the sensor temperature had been changed to 10 °C, and for 2 min after the temperature setting had been cancelled. The parameters analyzed were (1) skin temperature in a resting state before measurement (T rest), (2) mean skin blood flow in 1 min at a sensor temperature of 30 °C (F 30 °C), (3) minimum skin blood flow at a sensor temperature of 10 °C (F min), (4) slope of the blood flow plot during the period from the beginning of cooling at 10 °C to F min (S fall), (5) time required for the sensor temperature to reach 10 °C (Δt s), (6) maximum skin blood flow during the period from the end of cooling to the end of measurement (F max), (7) slope of the blood flow plot during the period from F min to F max (S rise), (8) rate of decrease of the skin blood flow during cooling: FDR = (F min/F 30 °C)×100, (9) recovery rate of the skin blood flow after the end of cooling: FRR = (F max/F 30 °C)×100. When correlations among the above nine parameters were evaluated by combining all age groups, significant correlations (P < 0.01) were observed between F 30 °C and F min, F 30 °C and F max, F 30 °C and S fall, F min and F max, and F max and S rise in the forehead. In the cheek, significant correlations (P < 0.01) were observed in all these combinations except between F max and S rise. When these analytical parameters were compared among the age groups, F 30 °C, T rest, F max, and S rise decreased significantly (P < 0.02 for F 30 °C and T rest, P < 0.01 for F max and S rise) and S fall increased significantly (P < 0.03) in the forehead with aging. However, no significant change with aging was observed in FDR, Δt s, F min, and FRR. In the cheek, FDR increased significantly (P < 0.03), and S rise decreased significantly (P < 0.01) with aging. However, no significant change with aging was observed in F 30 °C, T rest, F max, S fall, Δt s, F min, and FRR. Thus, the decrease in the skin blood flow during cooling showed no marked quantitative change with age, but, with aging, the rate of this decrease was clearly reduced in the forehead. In the cheek, on the other hand, the skin blood flow decreased markedly with aging, but no clear change was observed in the rate of this decrease. By using ILD-T and examining various parameters obtained, the skin hemodynamics in the forehead and cheek during cooling from 30 °C to 10 °C could be analyzed, and differences in the hemodynamics between the forehead and cheek and between elderly and younger individuals were clarified. This instrument is expected to be clinically useful.
Ettine Polak - One of the best experts on this subject based on the ideXlab platform.
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retinal blood flow changes in diabetic retinopathy measured with the heidelberg scanning laser Doppler Flowmeter
Graefes Archive for Clinical and Experimental Ophthalmology, 2000Co-Authors: Marinus H M Cuypers, Jocely S Kasanardjo, Ettine PolakAbstract:Background: Investigation of retinal blood flow in patients with and without diabetic retinopathy (DR). Retinal blood flow is measured with the non-invasive Heidelberg Retinal Flowmeter (HRF). The clinical suitability of the HRF in patients with diabetes mellitus is investigated, and measured blood flow is compared with blood flow in a group of non- diabetic persons. Methods: Cross- sectional study of retinal capillary perfusion in eighty diabetic patients and forty-nine control persons, non-invasively measured with the Heidelberg scanning laser Doppler Flowmeter. Results: In the control group, HRF measurements could be performed in all subjects. In the diabetes group some patients had media opacities or were not able to maintain stable fixation. Therefore HRF measurement was only possible in 79%, 75% and 60% of the subjects for the nasal, papillo-macular and foveal areas respectively. Retinal blood flow as measured in the perifoveal and nasal areas was associated with the level of diabetic retinopathy. In patients with proliferative DR (levels 4 and 5) the blood flow was reduced, in comparison with that of the patients with exudative or non-proliferative DR (levels 1 and 2) and preproliferative DR (level 3). Blood flow was not correlated with age, systemic blood pressure, intra-ocular pressure and perfusion pressure in either group. A significant negative correlation with the actual blood glucose level was found in the perifoveal area (R=–0.585, P=0.0001). Conclusions: The HRF offers an interesting non-invasive method for measurement of retinal blood flow. In this cross-sectional study variations in retinal blood flow could be detected in various stages of DR in relation to clinically visible funduscopic changes.
Christophe Chique - One of the best experts on this subject based on the ideXlab platform.
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compact laser Doppler Flowmeter ldf fundus camera for the assessment of retinal blood perfusion in small animals
PLOS ONE, 2015Co-Authors: Marielle Mentek, Frederic Truffe, Christophe Chique, Diane Godinribuo, Serge Amoos, Corinne Loeuille, Mario Ernabei, Martial GeiseAbstract:Purpose 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 signal did not significantly vary, suggesting that it could mostly be attributed to tissue light scattering. Conclusion We have demonstrated that, while not adapted for ONH blood perfusion assessment, this device allows pertinent, stable and repeatable measurements of retinal blood perfusion in rats.
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schlieren laser Doppler Flowmeter for the human optical nerve head with the flicker stimuli
Journal of Biomedical Optics, 2013Co-Authors: Martial Geise, Frederic Truffe, Hugo Evequoz, Hafid Khayi, Enjami Motte, Christophe ChiqueAbstract:We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the Flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination point. LDF measurements are based on heterodyne detection of Doppler shifted back-scattered light. We also describe an automated analysis of the LDF signals which rejects artifacts and false signals such as blinks. By using a Doppler simulator consisting of a lens and a rotating diffusing wheel, we demonstrate that velocity and flow vary linearly with the speed of the wheel. A cohort of 12 healthy subjects demonstrated that flicker stimulation induces an increase of 17.8% of blood flow in the ONH.
Marcelo T Nicolela - One of the best experts on this subject based on the ideXlab platform.
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scanning laser Doppler Flowmeter study of retinal and optic disk blood flow in glaucomatous patients
American Journal of Ophthalmology, 1996Co-Authors: Marcelo T Nicolela, Peter Hnik, Stephen M DranceAbstract:Purpose To examine blood flow in the retina and optic nerve head of patients with primary open-angle glaucoma. Methods Retinal and optic nerve head blood flow of glaucoma patients and control subjects of similar age and gender were measured in arbitrary units with the Heidelberg Retina Flowmeter, a scanning laser Doppler Flowmeter (Heidelberg Engineering, Heidelberg, Germany). A total of 33 glaucoma patients and 29 control subjects were included in this study. Microvascular blood volume, flow, and velocity were analyzed in four areas of the retina approximately 100 μm from the edge of the optic disk (two temporal, one superior, and one inferior), in one area of the neuroretinal rim, and in the lamina cribrosa. Results The glaucoma patients had significantly decreased blood volume, flow, and velocity in one temporal retinal area (P Conclusion These findings suggest that glaucoma patients tend to have less blood volume, flow, and velocity in the lamina cribrosa and upper temporal peripapillary retina. The temporal area below the horizontal, corresponding to the papillomacular bundle, did not show this difference. The findings may be significant in the pathogenesis of primary open-angle glaucoma.