Capillary Blood Flow Velocity Research Articles

Macular microcirculation in patients with epiretinal membrane before and after surgery

To investigate blood flow velocity (BFV) in the perifoveal capillaries before and after vitreous surgery for patients with epiretinal membrane (ERM). Twenty-one eyes in patients with ERM and 16 eyes in healthy subjects were involved in this study. Fluorescein angiography was performed using a scanning laser ophthalmoscope and BFV was analyzed by the tracing method. Foveal thickness (FT) was measured by optical coherence tomography. BFV was significantly slower in the ERM patients (1.04 ± 0.10 mm/s) than in the healthy subjects (1.49 ± 0.11 mm/s ) (p = 0.0010). BFV in the ERM patients 6 months after vitreous surgery (6 M) (1.21 ± 0.02 mm/s) significantly increased compared with BFV before surgery (0 M) (1.04 ± 0.10 mm/s) (p = 0.0061). BFV 1 year after vitreous surgery (1 Y) significantly increased (1.38 ± 0.02 mm/s) compared with BFV(6 M) (1.21 ± 0.02 mm/s) (p = 0.0235). FT was significantly greater in the ERM patients (351.7 ± 87.1 μm) than in the healthy subjects (158.9 ± 16.9 μm) (p = 0.0011). FT (6 M) significantly decreased (285.3 ± 36.9 μm) compared with FT before surgery (0 M) (351.7 ± 87.1 μm) (p = 0.0212). FT did not show significant differences between (6 M) and (1 Y). No significant correlation was found between BFV and FT before surgery. Perifoveal capillary BFV in patients with ERM was slower than that in the healthy subjects, and significantly improved after vitreous surgery as time progressed. It can be said that perifoveal capillary BFV is related to the development and improvement of ERM in the long term.

Tadalafil: a new role in Raynaud’s phenomenon?

exposure and protection of exposed skin during cold weather, although helpful, are often inadequate in protection. Pharmacological therapy with vasodilators such as calcium channel blockers or angiotensin II receptor antagonists have variable and moderate efficacy at best. Prostacyclins such as iloprost and its analog epoprostenol have been shown to result in good control of RP episodes, as well as healing of DUs; however, its use is limited by continuous intravenous infusions. Moreover, its half-life is short and hence not suitable for long-term therapy [4]. Oral analogs of prostacyclins lack the efficacy of the intravenous prostacyclins and results have been disappointing [5]. Recent studies with the endothelin-1 antagonist, bosentan, have shown it to prevent new DUs; however, paradoxically healing of the existing DUs was slowed [6]. Thus, there is a need for a drug that is easy to administer, safe and efficacious in the treatment of secondary RP. The phosphodiesterase-5 (PDE5) enzyme degrades cGMP, a molecule responsible for NO-mediated vasodilatation. PDE5 inhibitors, by inhibiting PDE5, increase the levels of cGMP, leading to vasodilatation. In addition, by inhibition of platelet activation it also improves microcirculation [7]. In a double-blind, placebocontrolled crossover trial involving 16 patients, sildenafil was effective in reducing the number of Raynaud’s attacks, as well as their severity. It also increased the capillary blood flow velocity measured by laser Doppler [8]. The short and fast action of sildenafil is ideal for the treatment of erectile dysfunction; however, it may not be suitable for chronic conditions such as RP, where a round-the-clock effect is required. Tadalafil is longer acting (half-life: 17.5 h), more specific for PDE5 and does not have the PDE6 inhibitory property, responsible Raynaud’s phenomenon (RP) is an exaggerated physiological phenomenon defined as episodic cold-triggered ischemic vasospasms of the digital arteries and precapillary arterioles. It can be idiopathic or may be a manifestation of underlying connective tissue diseases (CTDs) such as systemic lupus erythematosus, progressive systemic sclerosis (PSS; scleroderma), mixed connective tissue disease or rheumatoid arthritis. RP associated with CTDs is known as secondary RP [1]. It is more severe and causes tissue ischemia, resulting in digital ulcers (DUs). These DUs are often painful and cause progressive digital shortening with significant impairment of hand function and activities of daily living. DUs are a frequent complication in patients with PSS, with an estimated frequency of 17–30% [2].

Evaluation of perifoveal capillary blood flow velocity before and after vitreous surgery for epiretinal membrane

Evaluation of perifoveal capillary blood flow velocity before and after vitreous surgery for epiretinal membrane

Accuracy evaluation of RBC velocity measurement in nail-fold capillaries

Cutaneous red blood cell velocity in vivo can be measured by using capillaroscopy with image processing techniques. However, unlike simulated blood flow images, there is no standard to determine the accuracy of the techniques for computing blood flow velocities. In this paper, we quantitatively evaluated the accuracy of previously proposed optical flow method for measuring red blood cell velocity in nail-fold capillaries. Blood flow images of subjects under normal and occlusion-release conditions were examined by a capillaroscope. To obtain velocity values, the images were further analyzed by using optical flow, cross-correlation and visual inspection methods, respectively. Visual inspection method was taken as the golden standard to determine the accuracy of blood flow velocity measurement using optical flow and cross-correlation techniques. Results showed that optical flow estimation provided superior accuracy to cross-correlation when assessing real blood flow velocity in nail-fold capillaries. Optical flow estimation is able to measure red blood cell velocity with a high accuracy of 91% and 86% when the observed velocity is less than 0.5 mm/s under normal and occlusion-release conditions, respectively. In addition, optical flow method showed good agreement with visual inspection in determining blood flow velocity in both normal and occlusion-release conditions when the high-velocity zone is excluded.

318 Hypothermia; What Does it Do to Cerebral Oxygenation and Microcirculation?

Background: Hypothermia is becoming a commonly used treatment for newborns with hypoxic ischemic encephalopathy (HIE) with promising results. The cerebral metabolic effects have been studied extensively. However the acute effects on cerebral and peripheral oxygenation, fractional tissue oxygen extraction, and microcirculation still need further research.Methods: Newborns with HIE were cooled for 72 hours. Cerebral, peripheral oxygenation index were measured before, during and after hypothermia by near infrared spectroscopy (NIRS), microcirculation was assessed from axilla by sidestream dark field (SDF) imaging technique during and after hypothermia.Results: We present results of cerebral tissue oxygen index (cTOI) measured by (NIRS) from scalp, calculated cerebral fractional tissue oxygen extraction (cFTOE), microvascular flow index (MFI), % of vessels with sluggish flow measured by (SDF) technique in 5 newborns with HIE who underwent selective head cooling for 72 hours in figure.[Microcirculation and NIRS Data During Hypothermia]cTOI, cFTOE values were similar during hypo and normothermia, however microcirculation was much slower during hypothermia.Discussion: Selective head cooling causes minor effects on cerebral oxygenation measured by NIRS, however the repercussions of its effects on blood flow velocity in capillaries require further research.

Influence of macular microcirculation and retinal thickness on visual acuity in patients with branch retinal vein occlusion and macular edema

To investigate perifoveal capillary blood flow velocity and retinal thickness at the central fovea in patients with branch retinal vein occlusion (BRVO) and macular edema and to assess their relation with visual acuity and visual prognosis. Eighteen patients with BRVO and 16 healthy volunteers were compared. Perifoveal capillary blood flow velocity was measured on fluorescein angiograms with a scanning laser ophthalmoscope by the tracing method. Retinal thickness was measured at the central fovea by optical coherence tomography. Best-corrected visual acuity (BCVA) was determined. BCVA differed significantly between patients and controls (P < 0.0001). Among patients, BCVA was negatively correlated with perifoveal capillary blood flow velocity by univariate analysis (r = -0.7916, P < 0.0001), and positively correlated with retinal thickness at the central fovea (r = 0.8970, P < 0.0001). Multivariate analysis showed that retinal thickness at the central fovea was the only independent determinant of BCVA (P < 0.0001). In patients with BRVO, BCVA was more strongly influenced by retinal thickness at the central fovea than by perifoveal capillary blood flow velocity.

Erythropoietin inhibits post-ischemic leukocyte adhesion but does not affect rejection in murine cardiac allografts

This study was aimed to assess the pleiotropic effects of non-hematopoietic doses of erythropoietin (Epo) on post-ischemic microcirculatory dysfunction and inflammation in murine cardiac allografts. Epo was given intraperitoneally 2 hours prior to explantation (Epo-donor) or 2 hours prior to the onset of reperfusion (Epo-recipient). Controls were not treated. Intravital fluorescence microscopy (IVM) was used to assess post-ischemic coronary microcirculatory dysfunction. IVM exhibited decreasing capillary blood flow velocities and functional capillary densities (FCD) in controls. Capillary diameters and venular blood flow characteristics showed no significant changes over time. Epo-treatment had no effect on coronary microhemodynamics. Post-ischemic inflammation was characterized by augmented macromolecular leakage. Microvascular permeability decreased in the Epo-donor group (p < 0.05). Leukocyte rolling in coronary post-capillary venules decreased during reperfusion from 64 ± 16 to 19 ± 16 cells/min/mm, whereas firm adhesion increased from 333 ± 135 to 479 ± 154 cells/mm(2) in controls. Capillary leukocyte plugging remained stationary over time with approximately 4 to 6 cells/HPF. Firm adhesion was inhibited in the Epo-recipient group, resulting in 84 ± 34 cells/mm(2) at 6 hours of reperfusion (p < 0.05). Capillary leukocyte plugging was also reduced in the Epo-recipient group (p < 0.05). Epo exerted no effect on leukocyte rolling. Histology revealed significant myocardial edema formation in allografts, without any alteration by Epo treatment. Immunohistochemistry indicated the involvement of resident cardiac mast cells. Allograft rejection was not affected by Epo treatment. We demonstrate that non-hematopoietic treatment with Epo inhibits acute post-ischemic myocardial leukocyte sequestration, without affecting microcirculatory dysfunction and allograft rejection.

Association between macular microcirculation and soluble intercellular adhesion molecule-1 in patients with macular edema and retinal vein occlusion

In patients who have macular edema secondary to retinal vein occlusion, the role of vasoactive molecules such as growth factors and the influence of molecules related to leukocyte adhesion need to be investigated further. A prospective study was performed to investigate the relations between perifoveal capillary blood flow velocity and the vitreous levels of vascular endothelial growth factor (VEGF) and soluble intercellular adhesion molecule-1 (sICAM-1) in patients with macular edema and retinal vein occlusion. Undiluted vitreous specimens were obtained from 11 eyes of 11 patients with macular edema (nine had branch retinal vein occlusion and two had central retinal vein occlusion). VEGF and sICAM-1 levels were measured by enzyme-linked immunoabsorbent assay. Before vitreous sampling, perifoveal capillary blood flow velocity was measured by fluorescein angiography with a scanning laser ophthalmoscope and the tracing method. The relations between perifoveal capillary blood flow velocity and the vitreous levels of VEGF and sICAM-1 were investigated. There was a significant correlation between perifoveal capillary blood flow velocity and the vitreous level of sICAM-1 (rho = -0.7303, p = 0.03). In contrast, there was no significant association between blood flow velocity and the vitreous level of VEGF (rho = -0.1458, p = 0.67). The vitreous level of sICAM-1 is associated with perifoveal capillary blood flow velocity in patients who have retinal vein occlusion and macular edema.

Macular microcirculation before and after vitrectomy for macular edema with branch retinal vein occlusion

The changes of perifoveal capillary blood flow velocity (BFV), visual acuity, and retinal thickness after pars plana vitrectomy (PPV) have been unclear in patients with branch retinal vein occlusion (BRVO) and macular edema. In a prospective study, PPV was performed on six eyes of six consecutive BRVO patients with macular edema (two women and four men; mean age: 66.3 +/- 5.0 years). Patients were examined preoperatively and 6 months postoperatively. BFV was measured by fluorescein angiography using a scanning laser ophthalmoscope and the tracing method. Macular thickness was examined by optical coherence tomography. Visual acuity was measured preoperatively and postoperatively, and data were converted to the logarithm of the minimum angle of resolution (logMAR). In all six treated eyes, the macular thickness decreased significantly compared with before PPV (464 +/- 98 microm versus 224 +/- 55 microm, P = 0.0082), mean BFV increased significantly compared with before PPV (1.14 +/- 0.14 mm/sec versus 1.46 +/- 0.21 mm/sec, P = 0.0013), and mean logMAR decreased significantly compared with before PPV (0.57 +/- 0.34 versus 0.17 +/- 0.21, P = 0.0036). PPV may improve perifoveal microcirculation and the visual prognosis in BRVO patients with macular edema.

Macular microcirculation in hypertensive patients with and without branch retinal vein occlusion

Our purpose was to determine whether a reduction in blood flow velocity (BFV) in the perifoveal capillaries is involved in the pathogenesis of branch retinal vein occlusion (BRVO) in patients with hypertension. Subjects included hypertensive patients with (n = 12) and without (n = 16) BRVO and healthy volunteers (n = 16). Perifoveal BFV was measured by the tracing method using fluorescein angiography and a scanning laser ophthalmoscope. Logistic regression analysis was performed to assess factors that influenced the presence or absence of BRVO. Mean BFV showed a significant decrease across the three groups (healthy controls: 1.49 +/- 0.11 mm/second; hypertensive patients without BRVO: 1.36 +/- 0.12 mm/second; hypertensive patients with BRVO: 1.16 +/- 0.24 mm/second; p(trend) < 0.001). Multivariate logistic regression analysis showed that BFV was a significant risk factor for the presence of BRVO. Perifoveal capillary BFV is reduced in hypertensive patients with and without BRVO. It is possible that a decrease in BFV may be involved in the occurrence of BRVO. Measurement of perifoveal capillary BFV may be useful for investigating the pathogenesis and progression of BRVO.

Macular microcirculation and macular oedema in branch retinal vein occlusion

Background/aims:The relationship between the blood-flow velocity in the perifoveal capillaries and macular oedema was investigated in patients with branch retinal vein occlusion (BRVO).Methods:This study compared 18 patients with BRVO and...

Influence of various radiographic contrast media on the buckling of endothelial cells

The intra-arterial application of radiographic contrast media (RCM) can induce decreases of blood flow velocity in downstream capillaries as well as a decrease in the tissue oxygen tension. It is unclear whether changes in endothelial cell morphology contribute to the observed microcirculatory disorders. Four RCMs (Iodixanol320, Iohexol350, Iopromide370, and Imeron350) were added to the culture medium of human umbilical venous endothelial cells (HUVEC) and used for short-term incubation studies of these cells. Addition of Iohexol ( p = 0.6377) and Iodixanol ( p = 0.6309) did not affect the HUVEC height 1.5 min after incubation in the modified cell culture media supplemented with 30% v/v of the respective RCM. Strong buckling and increased endothelial height appeared after incubation in Iopromide-supplemented medium (the cell height increased by 95% compared to cells incubated under control conditions; p = 0.0065). Addition of Iomeprol-supplemented medium caused an increase by 61.6% compared to cells incubated under control conditions; p = 0.0051. After 5 min of incubation in any of the RCM-supplemented media, there was no difference in HUVEC height in comparison to incubation in control standard culture media (each p value > 0.05). The tremendous buckling caused by Iopromide and Iomeprol, coinciding with an echinocyte formation of erythrocytes might be the reason why a bolus injection of Iopromide in vivo into the left coronary artery was followed by a 50% decrease of oxygen partial pressure in the supplied tissue.

Dynamic oscillatory circuit of regulation of capillary hemodynamics

We used laser Doppler flowmetry with wavelet analysis of blood flow oscillations, computer capillaroscopy, and thermometry of the nail bed in 30 subjects to show an important role of the oscillatory circuit in the regulation of capillary hemodynamics, number of functioning capillaries, and linear and volumetric velocity of blood flow. The number of functioning capillaries is regulated by oscillations of myogenic and sensory peptidergic origin. The appearance of sensory oscillations, especially high-amplitude oscillations, is an adaptive neurotrophic mechanism that significantly increases the number of functioning capillaries and intensity of blood flow from arterioles to capillaries. The linear velocity of blood flow depends on both the tone of microvessels and changes in the dynamic component of blood pressure. Under conditions of skin hypoperfusion, the mean linear velocity of capillary blood flow may be inversely related to the extracapillary perfusion, including the amplitude of heart rate (A h) and oscillations of the tone of precapillary sphincters, whereas under conditions of vasodilation and increased skin perfusion, it may be inversely related to the amplitude of arteriolar oscillations of endothelial or neurogenic sympathetic origin (A maxe + n) and the shunting index. The A h affects the linear velocity of blood flow in the arterial part of capillaries, whereas the A maxe + n influences the same factor in the venous part. The contribution of oscillations to the regulation of the linear velocity varies depending on the perfusion and skin temperature. The resultant tone of distributing microvessels is determined by the competition between the stationary and oscillatory components. In addition to changes in the amplitude, the frequency of vasomotions may also be important. The regulatory importance of the oscillatory circuit is increased with a decrease in the skin blood flow.

Characteristics of Biphasic Slow Depolarizing and Slow Hyperpolarizing Potential in Frog Taste Cell Induced by Parasympathetic Efferent Stimulation

When the velocity of capillary blood flow in the frog tongue declined to an intermediate range of 0.2-0.7 mm/s, the glossopharyngeal nerve stimulation induced a biphasic slow depolarizing and slow hyperpolarizing potential (HP) in taste cells. The objective of this work was to examine the generative mechanisms of the biphasic slow potentials. The biphasic slow response was always preceded by a slow depolarizing potential (DP) component and followed by a slow HP component. Intravenous injection of tubocurarine completely blocked the biphasic slow responses, suggesting that both components of the biphasic slow potentials are evoked by the parasympathetic nerve (PSN) fibers. Membrane conductance of taste cells increased during slow DPs and decreased during slow HPs. The reversal potential of either component of a biphasic slow response was the almost same value of -12 mV. An antagonist, L-703,606, for neurotransmitter substance P neurokinin(1) receptor completely blocked both components of the biphasic slow responses. An antagonist, flufenamic acid, for nonselective cation channels on the taste cell membrane completely blocked the biphasic slow responses. These results suggest that PSN-induced biphasic slow responses are postsynaptically elicited in taste cells by releasing substance P at the PSN axon terminals. It is concluded that the slow DP component may be generated by opening one type of nonselective cation channel on taste cells and that the slow HP component may be generated by closing the other type of nonselective cation channel. We discussed that a second messenger inositol 1,4,5-trisphosphate might be related to a slow DP component and another second messenger diacylglycerol might be related to a slow HP component.

Relationship of Macular Microcirculation and Retinal Thickness with Visual Acuity in Diabetic Macular Edema

To assess perifoveal capillary blood flow velocity (BFV), capillary occlusion, and retinal thickness at the central fovea in diabetic patients with or without clinically significant macular edema; to examine the relationships of these variables with visual acuity (VA); and to identify their contributions to visual outcome and diabetic macular edema. Comparative cross-sectional prospective study. Diabetic patients with clinically significant macular edema (CSME) (n = 22), matched diabetic patients without CSME (n = 22), and healthy volunteers (n = 16). Capillary BFV was measured by fluorescein angiography using a scanning laser ophthalmoscope and was analyzed by the tracing method. Severity of perifoveal capillary abnormalities was classified by the size and outline of the foveal avascular zone (FAZ) and extent of foveal capillary loss. Macular thickness was measured by optical coherence tomography. Each subject underwent a complete ophthalmic evaluation, and best-corrected VA (BCVA) was converted to the logarithm of the minimum angle of resolution scale. Relationship of perifoveal capillary BFV, capillary occlusion, and foveal thickness with VA. Best-corrected VA significantly differed among all 3 groups (P<0.0001). Best-corrected VA correlated negatively with BFV (r = -0.644, P<0.0001) among all subjects and positively with retinal thickness at the central fovea in diabetic patients with CSME (r = 0.640, P = 0.0013). There was a positive correlation between BCVA and severity in the size of the FAZ (r = 0.484, P = 0.0015), outline of the FAZ (r = 0.542, P = 0.0004), and extent of foveal capillary loss (r = 0.585, P = 0.0001) among all diabetic subjects. Multiple regression analysis showed that retinal thickness at the central fovea was the only variable that significantly predicted VA (standardized regression coefficient, 0.635; P = 0.0001). Best-corrected VA was associated with perifoveal capillary BFV, severity of perifoveal capillary occlusion, and retinal thickness at the central fovea in diabetic patients, but the greatest contributing factor was only the retinal thickness.

Relationship between Macular Microcirculation and Progression of Diabetic Macular Edema

To investigate the relationship between blood flow velocity in perifoveal capillaries and retinal thickness at the central fovea in diabetic patients with clinically significant macular edema to elucidate the pathogenesis of diabetic macular edema. Comparative, cross-sectional, prospective study. Participants included diabetic patients with clinically significant macular edema (n = 22), matched diabetic patients without clinically significant macular edema (n = 22), and healthy volunteers (n = 16). Perifoveal capillary blood flow velocity was measured with fluorescein angiography using a scanning laser ophthalmoscope and was analyzed by the tracing method. The severity of perifoveal capillary abnormalities among diabetic patients without clinically significant macular edema was classified by the size and outline of the foveal avascular zone and extent of foveal capillary loss at the baseline by the use of fluorescein angiograms. Retinal thickness at the central fovea was measured by optical coherence tomography. Relationship between perifoveal capillary blood flow velocity and retinal thickness at the central fovea. Perifoveal capillary blood flow velocity was significantly slower in the patients with clinically significant macular edema (0.94+/-0.09 mm/second) compared with the patients without clinically significant macular edema (1.22+/-0.20 mm/second) and the healthy volunteers (1.49+/-0.11 mm/second; P<0.0001). Capillary blood flow velocity negatively correlated with retinal thickness at the central fovea (r = -0.4018, P<0.0001). Capillary blood flow velocity varied among diabetic patients without clinically significant macular edema, and there were significant negative correlations between capillary blood flow velocity and the size of the foveal avascular zone (r = -0.52, P = 0.01), the outline of the foveal avascular zone (r = -0.44, P = 0.04), and the extent of foveal capillary loss (r = -0.51, P = 0.01). The reduction of perifoveal capillary blood flow velocity may occur before the increase of retinal thickness at the central fovea in the diabetic patients. It is possible that long-term reduction of blood flow velocity increases retinal thickness of the macula and may play an important role in the development and the progression of diabetic macular edema.

Long-Term Palmar Microcirculation After Radial Artery Harvesting: An Observational Study

The aim of this study was to assess palmar microcirculation in a long-term follow-up after radial artery harvesting for coronary revascularization. One hundred fourteen patients (100 male; aged 61.7 +/- 6.7 years; preoperative New York Heart Association 2.3 +/- 0.6, ejection fraction 61.4% +/- 13.9%) were included after undergoing elective coronary revascularization using the radial artery of the nondominant forearm with a nonpathologic Allen's test. Superficial and deep tissue oxygen saturation (SO2), postcapillary venous filling pressure (rHb), capillary blood flow, and capillary blood flow velocity were determined at a mean 25 +/- 5 months after surgery using a combined laser Doppler spectrophotometry system. At 2-mm tissue depth, there was a small, but significant, decrease of 3% of superficial SO2 at the thumb and the thenar eminence (D1: 75.3% +/- 8.9% versus 77.6% +/- 9.7%, p = 0.003; thenar: 71.5% +/- 10.5% versus 73.2% +/- 8.2%, p = 0.027). Deep palmar SO2 was changed significantly at 5 of 7 positions by 3%. Deep postcapillary venous filling pressure (8 mm) was significantly increased by 9% only at the fingertip of the fifth finger (112.4 +/- 49.7 versus 103.0 +/- 25.0, p = 0.033), while superficial capillary blood flow decreased by 13% at only 1 of 7 positions at the hypothenar eminence (242.0 +/- 153.6 versus 275.6 +/- 169.2, p = 0.009). Overall, only 2 of 56 positions exceeded a given threshold of 5% change of microcirculation. No clinical signs of malperfusion were found (postoperative New York Heart Association 1.1 +/- 0.4, p < 0.05), and no patient was impaired in daily palmar motor activity. Long-term objective evaluation of superficial and deep palmar microcirculation confirms that radial artery harvesting for coronary revascularization does not compromise palmar microcirculation.

Tracing Method in the Assessment of Retinal Capillary Blood Flow Velocity by Fluorescein Angiography with Scanning Laser Ophthalmoscope

To evaluate the feasibility of a new method (the tracing method) for measuring perifoveal capillary blood flow velocity (BFV). The BFV in the perifoveal capillaries was measured in 12 eyes of healthy subjects and 12 eyes of patients with clinically significant macular edema (CSME) by fluorescein angiography using a scanning laser ophthalmoscope by either the tracing method or the conventional method. A randomized crossover design was employed to assign the subjects to each method. The number of capillaries recognized by the tracing method in healthy subjects and in patients with CSME was significantly higher than that recognized with the conventional method (P = 0.0134 and P = 0.0108, respectively). The number of fluorescent dots detected by the tracing method in healthy subjects and in patients with CSME was also significantly higher than that detected with the conventional method (P = 0.0002 and P = 0.0137, respectively). Accurate detection of the movement of fluorescent dots and analysis of BFV were possible with the tracing method. The BFV varied within each perifoveal capillary, and the mean BFV also varied according to capillary location in the macula. The new tracing method is useful for analyzing the retinal capillary BFV in healthy subjects and in patients with CSME.

Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

To investigate the quantitative response of retinal circulation in normal human eyes to oxygen and carbon dioxide provocation and to gain more information about retinal mean transit time (MTT). Healthy subjects were studied while breathing: room air (O(2) baseline); pure O(2); room air (CO(2) baseline), and CO(2) in room air. The CO(2) level was brought to 30% above individual baseline level. During each gas exposure, blue field simulation was used to estimate the velocity of macular leucocytes and fluorescein angiography was used to determine MTT, arteriovenous passage time (AVP) and vessel diameters. Breathing pure O(2) caused a reduction in macular leucocyte velocity of about 13%, a non-significant change in MTT and AVP from baseline, and a 10% reduction in the diameter of temporal retinal arteries and veins. Breathing CO(2) caused an increase in macular leucocyte velocity of 21%, a non-significant change in MTT and AVP, and no change in retinal vascular diameters. Both O(2) and CO(2) had the expected effects on retinal blood flow, as judged by leucocyte velocity in the macular capillaries, but little effect on retinal MTT, indicating concomitant changes in flow and retinal vascular volume. Measuring the diameter of retinal vessels before and during pure O(2) breathing is a simple and effective way of determining the reactivity of retinal vessels.

Sildenafil in the Treatment of Raynaud’s Phenomenon Resistant to Vasodilatory Therapy

Vasodilatory therapy of Raynaud's phenomenon represents a difficult clinical problem because treatment often remains inefficient and may be not tolerated because of side effects. To investigate the effects of sildenafil on symptoms and capillary perfusion in patients with Raynaud's phenomenon, we performed a double-blinded, placebo-controlled, fixed-dose, crossover study in 16 patients with symptomatic secondary Raynaud's phenomenon resistant to vasodilatory therapy. Patients were treated with 50 mg sildenafil or placebo twice daily for 4 weeks. Symptoms were assessed by diary cards including a 10-point Raynaud's Condition Score. Capillary flow velocity was measured in digital nailfold capillaries by means of a laser Doppler anemometer. While taking sildenafil, the mean frequency of Raynaud attacks was significantly lower (35+/-14 versus 52+/-18, P=0.0064), the cumulative attack duration was significantly shorter (581+/-133 versus 1046+/-245 minutes, P=0.0038), and the mean Raynaud's Condition Score was significantly lower (2.2+/-0.4 versus 3.0+/-0.5, P=0.0386). Capillary blood flow velocity increased in each individual patient, and the mean capillary flow velocity of all patients more than quadrupled after treatment with sildenafil (0.53+/-0.09 versus 0.13+/-0.02 mm/s, P=0.0004). Two patients reported side effects leading to discontinuation of the study drug. Sildenafil is an effective and well-tolerated treatment in patients with Raynaud's phenomenon.