Velocity Of Central Retinal Artery Research Articles

Waveform parameters of retrobulbar vessels in glaucoma patients with different demographics and disease severity.

To identify novel velocity waveform parameters of the ophthalmic artery and central retinal artery by computer-aided image processing of Doppler ultrasonography measurements, and to evaluate correlations between the waveform parameters and different demographics and disease severity of open-angle glaucoma patients. Thirty-six images of 36 open-angle glaucoma patients were considered. A semiautomated image processing code was used to detect the digitalized ophthalmic artery and central retinal artery velocity waveforms and to extract the waveform parameters. Concordance correlation coefficient, two-sample t-test, and Pearson's correlation coefficient were used to test for similarities, differences, and associations among variables. Female glaucoma patients showed a statistically higher ophthalmic artery normalized distance between ascending and descending limb (p = 0.004), hypertensive glaucoma patients a statistically higher ophthalmic artery peak systolic velocity time (p = 0.025), glaucoma patients with hyperlipidemia a statistically higher ophthalmic artery resistivity index (p = 0.023) and a statistically higher ophthalmic artery peak systolic velocity acceleration (p = 0.025), glaucoma patients with cardiovascular diseases a statistically lower central retinal artery normalized distance between ascending and descending limb of the wave (p = 0.033) and a statistically higher central retinal artery period (p = 0.028), and patients with different body mass index a statistically different central retinal artery normalized distance between ascending and descending limb of the wave (p = 0.016). Groups with different disease severity, classified following the Brusini glaucoma staging system 2, showed statistically different central retinal artery normalized distance between ascending and descending limb of the wave (p < 0.001) and central retinal artery period (p = 0.016). No statistical differences were found in regard to race, diabetes status, glaucoma family history, and smoking. Ophthalmic artery and central retinal artery computer-aided analysis of velocity waveforms could identify novel waveform parameters capable of differentiating among different demographics and disease severity of open-angle glaucoma patients.

Advanced vascular exams improve the accuracy of conventional parameters in distinguishing normal tension from primary open angle glaucoma

PurposeThe role vascular factors play in glaucoma is still not fully understood. We aim to understand if advanced vascular exams can improve our ability to distinguish primary open angle glaucoma (POAG) from normal tension glaucoma (NTG) patients.MethodsWe applied multivariate logistic regression on the Leuven Eye Study data (182 NTG and 202 POAG patients), and created three prediction models. One with conventional parameters, one with parameters from advanced vascular exams [colour Doppler imaging (CDI), retinal oximetry, ocular pulse amplitude and choroidal thickness] and one where both kinds of parameters were allowed in (mixed). The area under the curve (AUC) was calculated and compared between them. Intra‐ocular pressure (IOP) and IOP‐related variables were excluded.ResultsThe conventional model included Raynaud phenomenon, mean arterial pressure (MAP), central corneal thickness, migraine, visual field mean deviation (VF MD), cup‐disc (C/D) ratio, visual acuity and mean retinal nerve fiber layer (mRNFL) thickness (in decreasing order of importance). The advanced vascular model included parameters from CDI and retinal oximetry. The mixed model included Raynaud phenomenon, MAP, arterio‐venous retinal oxygen saturation difference, acceleration (acc) of central retinal artery (CRA), end‐diastolic velocity of CRA, resistive index of ophthalmic artery, VF MD, C/D ratio, mRNFL thickness, acc of temporal posterior ciliary artery and migraine (in decreasing order of importance). The AUCs were 0.687, 0.677 and 0.743, respectively. The mixed model was able to significantly increase the prediction ability of the conventional model (p = 0.049).ConclusionsAdding advanced vascular exams increased the accuracy of the conventional model to distinguish between groups. These results show how important vascular factors can be in the pathogenesis of glaucoma.

Prolonged postocclusive hyperemia response in patients with normal-tension glaucoma.

BackgroundIt is believed that endothelial dysfunction may be a link between systemic and ocular dysregulation in glaucoma. The aim of this study was to evaluate peripheral vascular reactive hyperemia in response to occlusion test and to correlate peripheral vascular findings with retrobulbar hemodynamics parameters in patients with normal-tension glaucoma.Material/MethodsForty-eight patients with normal-tension glaucoma (mean age 58.1 years, 38 women) and 40 control subjects (mean age 54.1 years, 36 women) were subjected to a brachial arterial occlusion test and color Doppler imaging (LOGIQ 9, GE Medical Systems) of the retrobulbar arteries. Finger hyperemia was assessed by using a 2-channel laser Doppler flowmeter (MBF-3D, Moor Instruments, Ltd.). Time parameters (time to peak flow, half-time of hyperemia, time of recovery) and amplitude parameters (maximum hyperemia response, biological zero) of the post-occlusive reactive hyperemia signal pattern as well as velocities and resistance index of the ophthalmic, central retinal, and short posterior ciliary arteries were evaluated and compared between study groups.ResultsIn glaucoma patients, time to peak flow and half-time of hyperemia were significantly longer (21.4 vs. 12.0 s, p=0.02 and 74.1 vs. 44.2 s, p=0.03, respectively) and biological zero was significantly lower (2.4 vs. 3.2, p=0.01) comparing with healthy subjects. In glaucoma patients, peak-systolic and end-diastolic velocities of central retinal artery were significantly lower (12.8 vs.14.1, p=0.03 and 3.9 vs. 4.7, p=0.01, respectively) and resistance index of this artery was significantly higher (0.69 vs. 0.67, p=0.03) compared to controls. In the glaucoma group, maximum hyperemic response was negatively correlated with the resistance index of temporal short posterior ciliary arteries (r=−0.4, p=0.01), whereas in the control group half-time of hyperemia was negatively correlated with end-diastolic velocity of the central retinal artery (r=−0.3, p=0.03).ConclusionsArterial occlusion test elicited a prolonged systemic hyperemia response in patients with glaucoma as compared with healthy subjects. Retrobulbar blood flow alterations in glaucoma patients may be related to systemic vascular dysregulation.

Extraocular blood flow in multiple sclerosis (MS) patients

AbstractPurpose Buckground: Multiple sclerosis is autoimmune disease which is often associated with vascular dysregulation syndrome (VDS), mediated by endothelin‐1 (ET‐1). Vascular dysregulation syndrome can lead to diminished blood flow in eyeball arteries. The aim of this study is evaluation of retrobulbar hemodynamics in multiple sclerosis (MS) patients.Methods Material of this study consisted of 76 eyes of 38 MS patients (8 males and 30 females, mean age 39,38 years, range : 22‐56 years, SD: 10.02 ) which were recruited from Neurology and Epileptology Department. The healthy controls consisted of 52 eyes of 26 patients ( 3 males and 23 females, mean age: 36.26 years, range: 19‐55 years, SD: 10.88). No patients in the active stage of the disesses. The peak systolic (PSV) and‐ diastolic (EDV) blood flow velocities, indicators of peripheral vascular resistance such as Gosling Index (PI) and Pourcelot Index (RI) of the ophthalmic artery (OA), lateral short posterior ciliary arteries (LSPCA) and central retinal artery (CRA) were measured in each eye, using color Doppler imaging (CDI). In order to compare examined eyes between two groups we used analyze of variance (Unianowa). Additionaly, we analyzed the obtained values of blood flow in patients who received immunomodulation therapy and in patients who passed neuritis optica in history.Results Statistically significant disturbances in the examined eyeball arteries were found in CRA and OA. The affected parameters were: diminished PSV velocity in CRA and OA; EDV in CRA (border of statistical significance); PI, RI in OA and increased EDV in OA.Conclusion This study suggests that in MS eyes may exists of retrobulbar hemodynamics impairment.

Calculation of central retinal artery diameters in patients with type 1 diabetes using non‐invasive measurements

AbstractPurpose To compare the diameter of the central retinal artery between patients with type 1 diabetes and healthy control subjects in vivo. Central retinal artery diameters were calculated from results of non‐invasive measurements of ocular hemodynamics.Methods 16 patients with type 1 diabetes with no or mild diabetic retinopathy and 16 age‐matched healthy controls were participated in this study. Total retinal blood flow was assessed by the use of laser Doppler velocimetry and measurement of retinal vessel diameters in all veins entering the optic disc using a Dynamic Vessel Analyzer. In addition blood flow velocity in the retrobulbar central retinal artery was measured using color Doppler imaging. The diameter of the central retinal artery was then calculated individually for each subject using the obtained ocular hemodynamic data.Results Calculated central retinal artery diameters were significantly larger in patients with diabetes (180 ± 13 µm) compared to healthy controls (166 ± 10 µm, p = 0.001). There were no significant differences in retinal blood flow, retinal vessel diameters or mean flow velocity in the central retinal artery between the two groups.Conclusion The present results indicate a dilation of the central retinal artery in patients with type 1 diabetes, whereas total retinal blood flow is unaltered compared to healthy controls. Results from blood flow velocity measurements using color Doppler imaging in retrobulbar vessels do not include information about vessel diameters and need to be interpreted with caution in terms of retinal blood flow.

Kidney-Pancreas Transplantation Does Not Improve Retinal Arterial Flow Velocities in Type 1 Diabetic Uremic Patients

Kidney-Pancreas Transplantation Does Not Improve Retinal Arterial Flow Velocities in Type 1 Diabetic Uremic Patients

A Comparative Study of Bimatoprost and Travoprost: Effect on Intraocular Pressure and Ocular Circulation in Newly Diagnosed Glaucoma Patients

Background: This study compares intraocular pressure (IOP)-lowering efficacy and retrobulbar hemodynamic effects of bimatoprost and travoprost in patients with newly diagnosed open-angle glaucoma. Methods: Patients were randomly assigned to one of two treatment groups (bimatoprost group, n = 36; travoprost group, n = 46). IOP levels were measured with Goldmann applanation tonometer. Peak systolic velocity, end-diastolic velocity and resistivity index were obtained for each vessel by color Doppler imaging. Results: Both bimatoprost and travoprost significantly lowered IOP on days 30, 90 and 180 (p < 0.001). There was no significance between the 2 drugs on all follow-up visits. End-diastolic velocity of central retinal artery on day 180 was significantly higher than the value obtained at baseline in both groups. Conclusions: Patients were likely to achieve and maintain low target IOP with both drugs. Both drugs also resulted in improvement in the central retinal artery blood flow.

The Effect of Timolol-Dorzolamide and Timolol-Pilocarpine Combinations on Ocular Blood Flow in Patients With Glaucoma

To investigate the effect of timolol-dorzolamide and timolol-pilocarpine fixed combinations on retrobulbar vessel blood flow. Prospective, randomized, masked, crossover clinical trial. Sixteen patients with primary open angle glaucoma, treated with timolol 0.5%, received timolol 0.5%-dorzolamide 2% and timolol 0.5%-pilocarpine 2% for four weeks each. Heart rate, blood pressure, intraocular pressure (IOP), and peak systolic (PSV) and end diastolic velocities (EDV) in ophthalmic, central retinal, and short posterior ciliary arteries were measured before and after each treatment, and resistivity index was calculated. The IOP was reduced (P < .01) by timolol-dorzolamide and, more effectively, timolol-pilocarpine combinations. In central retinal artery, the end diastolic velocity was increased by the timolol-dorzolamide combination (P < .01), resulting in higher end diastolic velocity and lower resistivity index values (both P < .01) compared with the timolol-pilocarpine combination. The timolol-dorzolamide combination increases the end diastolic velocity in central retinal artery, despite a lower intraocular pressure decrease, suggesting an effect on retinal circulation.

Early Increase of Retinal Arterial and Venous Blood Flow Velocities at Color Doppler Imaging in Brittle Type 1 Diabetes after Islet Transplant Alone

Little information is currently available about the role of islet transplantation alone (ITA) on the retinal microcirculation. Our purpose was to investigate with color-Doppler-imaging the effect of ITA after one year on the blood flow velocities of central retinal artery and vein. Central retinal arteries and veins of both eyes of 10 ITA patients were evaluated with color-Doppler-imaging before and one year after transplant. Peak systolic velocity (psv), end diastolic velocity (edv) for arteries and maximum velocity (maxv), minimum velocity (minv) for veins were recorded and compared with a control group of type 1 diabetic patients. At one year, a statistically significant increase of blood flow velocities of central retinal arteries (psv: 6.09+/-0.46 vs. 10.12+/-1.20 cm/s, P=0.01) and veins (maxv: 3.12+/-0.28 vs. 6.12+/-1.00 cm/s, P=0.01) was found only in the ITA patients. An early, significant increase of arterial and venous retinal blood flow velocities was found after ITA.

The effect of surgical treatment on thyroid-associated ophthalmopathy

To evaluate the effect of muscle surgery on strabismus caused by extraocular muscle for thyroid-associated ophthalmopathy (TAO), and assess the change of vision acuity, intraocular pressure, visual field and blood flow velocity in central retinal artery that made by surgery treatment. Recession and release of the extraocular muscles were used in 17 TAO patients (20 eyes) with strabismus caused by the change of extraocular muscles. In those patients one of them was undergone superior rectus tendon resection and other one was undergone superior rectus suspension. Another patient right eye was undergone inferior rectus recession and the left one with superior rectus recession. For rest of 14 patients with 17 eyes inferior rectus recession was performed. The vision acuity, intraocular pressure, visual field, and blood flow velocity in central retinal artery were measured pre- and post-operatively. In 17 patients (20 eyes), 5 eyes vision acuity improved two or more lines and 15 eyes was unchanged postoperatively. Intraocular pressure and mean defect of visual field showed statistically significance (P < 0.01). The peak systolic velocity (PSV) and the end diastolic velocity (EDV) were significantly increased, and the resistance index (IR) was significantly reduced (P < 0.05). Muscle surgery of strabismus caused by extraocular muscle for TAO in the quiescent period can eliminate strabismus, decrease intraocular pressure, improve visual field and blood flow velocity in central retinal artery.

The effects of sildenafil on ocular blood flow

To investigate the effects of sildenafil, a popular new drug in the treatment of erectile dysfunction, on ocular blood flow. This study was designed as a prospective, double-blind, placebo-controlled study. Twenty participants with erectile dysfunction were given a single oral dose of 100 mg sildenafil, while 10 participants with erectile dysfunction were given placebo. All the participants underwent routine systemic and ophthalmological examinations. Intraocular pressure, systolic and diastolic blood pressure and ocular blood flow (ophthalmic, central retinal, short posterior ciliary arteries) were measured in both eyes before and 1 hour after the dose of sildenafil or placebo. Ocular blood flow measurements were performed using colour Doppler ultrasonography. None of the parameters were significantly different between the groups before study drug intake. Although central retinal artery velocities were not changed, ophthalmic artery and short posterior ciliary artery peak systolic velocity, end-diastolic velocity, and mean velocity values were significantly increased 1 hour after drug intake in the sildenafil group compared to the placebo group (p < 0.05). Sildenafil causes a significant increase in blood flow in these arteries. A possible role of inhibition of phosphodiesterase-5 in vascular smooth muscles by sildenafil is implicated. Further studies are needed to investigate the effects of sildenafil on ocular blood flow in patients with senile macular degeneration, diabetic retinopathy and glaucoma.

Sevoflurane effects on retrobulbar arteries blood flow in children

Measure of blood flow velocity in retrobulbar vessels is performed to determine the severity of ophthalmic pathologies as glaucoma. In children, this measure is usually performed under general anaesthesia. Sevoflurane is known to not modify cerebral blow flow velocities. However, its effect on retrobulbar circulation is not known. This study was designed to evaluate the effect of sevoflurane on retrobulbar circulation flow velocity in children undergoing examination for ocular disorders under general anaesthesia. Thirteen mechanically ventilated children (Fi(O2))=1) were included. Blood flow velocities of central retinal artery, ophthalmic artery, and middle cerebral artery were measured by Doppler ultrasound during 1 and 2 age-adjusted minimal alveolar concentration (MAC) sevoflurane anaesthesia. Intra-ocular pressure and non-invasive haemodynamic parameters were also measured. End-tidal carbon dioxide tension was controlled during all the study period. Mean arterial pressure decreased from 1 to 2 age-adjusted MAC sevoflurane (58 [12] vs 54 [12] mm Hg, P=0.01). In the ophthalmic artery, end diastolic velocity (EDV) decreased significantly at 2 MAC (1 MAC: 4.4 [4] cm s(-1) vs 2 MAC: 1.4 [2.4] cm s(-1); P=0.04) and resistivity index (RI) increased significantly (1 MAC: 0.83 [0.11] vs 2 MAC: 0.93 [0.09]; P=0.007). Systolic velocity, EDV, and RI remained constant in the central retinal artery and in the middle cerebral artery. High alveolar concentration of sevoflurane decreased blood flow velocity in the ophthalmic artery, but not in the central retinal and the middle cerebral arteries in children ventilated in hyperoxic condition. This effect was related to a decrease in mean arterial pressure. This vessel-dependent effect may be explained by the different autoregulatory mechanisms of these arteries. In the present hyperoxic conditions, the vascular effect of sevoflurane may have been limited in the central retinal artery and not in the ophthalmic artery.

Study on the Progression of Visual Field Defect and Clinical Factors in Normal-Tension Glaucoma

Purpose: We investigated the relationship between the progression of visual field defect and clinical factors in patients with normal-tension glaucoma (NTG). Subjects and Methods: Forty-eight eyes of 48 NTG patients undergoing more than 5-year follow-up were enrolled in this study. Their visual field defects ranged between Aulhorn's classification stage 2 and 4, and mean deviation (MD) more than −10 dB measured by Humphrey Field Analyzer (HFA). End points of this follow-up study were defined as follows: in HFA STATPAC 2 glaucoma change probability analysis, more than 5 points which significantly deteriorated at P < .05 were found at 2 consecutive examinations (Criterion 1) or a significant decrease in MD value at P < .025 was encountered at one examination or in MD value at P < .05 at consecutive examinations (Criterion 2). Results: During the follow-up period, 18 eyes of 48 patients satisfied Criterion 1 and 21 eyes Criterion 2. There were no significant differences in clinical factors between patients with progression and without progression. By multiple logistic regression analysis, minimum flow velocity of central retinal artery (CRA) showed significant relation (odds ratio for a 1 cm/sec rise = 0.2215; 95% confidence interval: 0.0530–0.9253) to progression of visual field defect in Criterion 1, and minimum flow velocity of CRA (odds ratio for a 1 cm/sec rise = 0.2099; 95% confidence interval: 0.0506–0.8712) and cholesterol (odds ratio for a 1 cm/dl rise = 1.0332; 95% confidence interval: 0.4096–2.6064) showed significant relation in Criterion 2. Conclusion: These results suggests that vascular risk factors of ocular blood flow may play a role in the progression of visual field defects in NTG patients.

Color Doppler image of central retinal artery of eyes with an intraconal mass

Purpose. Retinal ischemia secondary to hypoperfusion of the central retinal artery is recognized as one factor that may contribute to the development of loss of vision in eyes with intraorbital tumors. We study intraorbital tumors which produce motility disturbances and visual problems by color Doppler imaging to evaluate this factor. Methods. We examined the central retinal artery velocities of 3 patients with disc edema caused by intraconal masses (2 cavernous hemangiomas and 1 presumed optic nerve glioma) via color Doppler imaging. Results. The time-velocity waveform demonstrated abnormally high vascular resistance in the central retinal artery of all affected eyes in the primary position compared with the normal waveform seen in the other eyes. We compared the pulsatility index of eyes with an intraconal mass and contralateral, control eyes using Student’s t test for paired samples and significant differences were noted between both groups (p <0.01). Conclusions. Intraconal tumors could produce increased pressure in the optic nerve sheath and the optic nerve tissue which could be associated with impaired retinal and optic nerve blood flow and the subsequent amaurosis encountered with intraorbital tumors.

Flow velocity of central retinal artery and retrobulbar vessels during cardiovascular operations

Objective: Both blood flow monitoring and pressure monitoring are necessary to avoid inadequate cerebral perfusion during cardiovascular operations. Inasmuch as transcranial Doppler ultrasonography does not provide a consistently good signal, especially during cardiopulmonary bypass, we examined the blood flow through the central retinal artery, which has proved to reflect an obstruction of the carotid artery. Method: Twenty-eight consecutive cases were examined with a 5 or 7.5 MHz conventional echocardiographic probe. Correlation between the maximal velocity at the central retinal artery and systolic blood pressure was examined. The blood flow of the central retinal artery and retrobulbar vessels was examined during selective or retrograde cerebral perfusion or intraaortic balloon pumping. Results: Blood flow could be clearly visualized but disappeared below a certain pressure in every case. With data from 478 measuring points, systolic blood pressure correlated with maximal velocity ( r = 0.6902, p < 0.0001). The blood pressure–axis intercept, known as “critical closing pressure,” was 35.8 ± 14.8 mm Hg, varying among individuals and bilateral eyes. Pulsatility index increased after cardiopulmonary bypass (1.095 ± 0.245 to 1.525 ± 0.268, p < 0.0001). Patency of the circle of Willis was confirmed by the blood flow during anastomosis of the ipsilateral artery. During retrograde cerebral perfusion, blood flow was detectable at the retrobulbar vessels. During intraaortic balloon pumping, the central retinal artery flow was augmented on inflation of the balloon. Conclusion: Orbital vessel monitoring provides the critical closing pressure of the central retinal artery and confirms patency of the circle of Willis. The eye can be “an acoustic window” into intracranial blood flow during cardiovascular surgery. (J Thorac Cardiovasc Surg 1997;114:1081-7)

Reversible Abnormalities in the Ophthalmic Arteries Detected by Color Doppler Imaging

To demonstrate dynamic, reversible abnormalities in ophthalmic artery blood flow velocity identified with color Doppler imaging (CDI) in patients with clinical findings of ocular ischemia with and without carotid artery stenosis. One patient with ocular ischemia and normal carotid arteries had abnormal ophthalmic artery velocities demonstrated by CDI. Two other patients with reversed ophthalmic artery flow and critical internal carotid artery stenosis were studied before and after carotid endarterectomy. Peak systolic and diastolic velocities as well as pulsatility indices of ophthalmic, posterior ciliary, and central retinal arteries were calculated. The patient who had ocular ischemic syndrome without carotid artery stenosis showed increased ophthalmic artery velocities initially, and reversal of flow within the ophthalmic artery subsequently developed. Clinical findings and symptoms improved gradually as ophthalmic artery, posterior ciliary, and central retinal artery velocities increased. The patients with critical internal carotid artery stenosis had reversed ophthalmic artery blood flow initially which reverted to normal after carotid endarterectomy. Ocular ischemic syndrome may occur due to abnormal blood flow in the ophthalmic artery in the absence as well as in the presence of carotid artery stenosis. Flow dynamics in the ophthalmic artery and its branches can be shown by CDI to revert toward normal as the clinical findings improve spontaneously or after opening an occluded carotid artery.

Variability in measurement of central retinal artery velocity using color Doppler imaging.

The purpose of our study was to test the reproducibility of the central retinal artery velocity measurements as made by color Doppler imaging and pulsed Doppler spectral tracings and to define the optimal location for placement of the sample volume. We used the Siemens Quantum (Q 2000) with a 7.5 MHz linear array transducer to identify the central retinal artery and record its velocity. Eleven eyes from 11 normal subjects were evaluated for the peak systolic central retinal artery velocity in two positions, the first posteriorly in the optic nerve at an average of 3.56 mm from the surface of the optic disc and the second at an average of 1.76 mm from the surface of the optic disc. We then used a color-flow threshold to identify and record the point of maximal velocity. The range of systolic velocities in the 11 eyes was from 5.85 to 22.51 cm/sec. The peak systolic velocity posteriorly in the optic nerve averaged 8.16 cm/sec, whereas near the surface of the optic disc the velocity averaged 13.89 cm/sec (70.2% higher). Using the color flow threshold method, the maximal velocity was located at an average of 1.98 mm from the surface of the optic disc. Our data show that large differences exist in measured central retinal artery velocity that depend on the location of the measurement, and that color-flow thresholding is valuable in locating the optimal location for pulsed Doppler spectral recording.