Non-contact, two-dimensional measurement of tissue circulation in choroid and optic nerve head using laser speckle phenomenon

Association Between Optic Nerve Head Blood Flow Measured Using Laser Speckle Flowgraphy and Radial Arterial Pressure During Aortic Arch Surgery

OBJECTIVE

This study was designed to investigate the association between ocular blood flow measured using laser speckle flowgraphy (LSFG) and radial arterial pressure during aortic arch surgery.

DESIGN

A prospective study.

SETTING

A single university hospital.

PARTICIPANTS

This study included 24 patients undergoing aortic arch surgery with cardiopulmonary bypass (CPB) using antegrade selective cerebral perfusion (SCP).

INTERVENTIONS

Measurement of optic nerve head blood flow using LSFG and radial arterial pressure via a catheter in the radial artery METHODS AND MAIN RESULTS: Antegrade SCP was managed with 24℃ and 40-to-60 mmHg at the right radial artery, which usually corresponds to a flow rate of 10 mL/kg/min. Optic nerve head blood flow using LSFG and radial arterial blood pressure were evaluated simultaneously at the right side and recorded at the following 4 points: after the induction of anesthesia (phase 1), after the beginning of CPB (phase 2), after the beginning of antegrade SCP (phase 3), and after cessation of CPB (phase 4). A moderate positive correlation between %change of mean blur rate in the optic nerve head measured using LSFG and %change of radial mean arterial pressure was identified (r = 0.604, p < 0.001). Bland-Altman analysis showed that the bias (mean difference) was -1.2% (95% limits of agreement -47.4% to 45.0%), indicating good agreement between %changes of the values recorded using the 2 measurements.

CONCLUSIONS

Intraoperative monitoring of optic nerve head blood flow using LSFG can be used as an additional cerebral perfusion parameter during aortic arch surgery with CPB using antegrade SCP.

Retinal Blood Flow Velocity Change in Parafoveal Capillary after Topical Tafluprost Treatment in Eyes with Primary Open-angle Glaucoma

Although ocular circulation at the retina and optic disc is known to be associated with the pathology of glaucoma, direct measurement of blood flow velocity has been difficult to obtain. This prospective observational study enrolled 11 consecutive patients with treatment-naïve primary open-angle glaucoma (POAG) and 11 healthy subjects, and the effects of topical tafluprost treatment on ocular circulation were examined at baseline and at 1, 4, and 12 weeks after initiating treatment with topical tafluprost on POAG patients using multiple modalities, which include adaptive optics scanning laser ophthalmoscopy (AOSLO). Baseline mean intraocular pressure (IOP) was significantly higher and mean parafoveal blood flow velocity (pBFV) was significantly lower in POAG eyes than in healthy eyes. Mean IOP was significantly decreased (1 week, −19.1%; 4 weeks, −17.7%; and 12 weeks, −23.5%; all P < 0.001) and mean pBFV was significantly increased from the baseline at all follow-up periods after initiating treatment (1 week, 14.9%, P = 0.007; 4 weeks, 21.3%, P < 0.001; and 12 weeks, 14.3%, P = 0.002). These results reveal that tafluprost may not only lower IOP but may also improve retinal circulation in POAG eyes and AOSLO may be useful to evaluate retinal circulatory change after treatment.

Differences in optic nerve head microcirculation between evening and morning in patients with coronary artery disease

PURPOSE

To determine whether differences or variation of blood flow in the ONH are independent risk factors for CAD.

METHODS

We studied 144 consecutive patients whose ocular blood flow in the ONH was measured in the evening and morning by LSFG. We analyzed the MBR throughout the ONH (MBR-A) and in the tissue (MBR-T) and vessels (MBR-V) in the ONH. We also evaluated the MBR-T, MBR-V, and MBR-A values obtained in the evening and morning and the variation (Δ) between evening and morning values in each group.

RESULTS

Twenty-three patients (16%) were diagnosed with CAD. The morning MBR-T and MBR-A values were significantly lower in these patients with CAD compared to the patients without CAD. ΔMBR-T in the CAD patients was significantly lower compared to that of the no-CAD patients. The logistic regression analysis was revealed that a high carotid artery plaque score, lower ΔDBP, and ΔMBR-T were identified as risk factors for CAD.

CONCLUSIONS

Ocular microcirculation obtained from LSFG may provide a window for detecting changes in microvasculature related to CAD.

Evaluating ocular blood flow

Studies have shown that vascular impairment plays an important role in the etiology and pathogenesis of various ocular diseases including glaucoma, age-related macular degeneration, diabetic retinopathy, and retinal venous occlusive disease. Thus, qualitative and quantitative assessment of ocular blood flow (BF) is a topic of interest for early disease detection, diagnosis, and management. Owing to the rapid improvement in technology, there are several invasive and noninvasive techniques available for evaluating ocular BF, with each of these techniques having their own limitations and advantages. This article reviews these important techniques, with a particular focus on Doppler Fourier domain optical coherence tomography (OCT) and OCT-angiography.

Association between Optic Nerve Head Microcirculation and Macular Ganglion Cell Complex Thickness in Eyes with Untreated Normal Tension Glaucoma and a Hemifield Defect

Purpose. We evaluated the association between optic nerve head (ONH) microcirculation and macular ganglion cell complex (mGCC) thickness in patients with untreated normal tension glaucoma (NTG) and a hemifield defect. Methods. The medical records of 47 patients with untreated NTG were retrospectively reviewed. Laser speckle flowgraphy was used to obtain mean blur rate (MBR), a relative measure of blood flow. Average total deviation (TD), mGCC, and the circumpapillary retinal nerve fiber layer (cpRNFL) thickness were also analyzed. Results. All parameters corresponding to the defective hemifield were significantly lower than those corresponding to the normal hemifield. In the defective hemifield, MBR was correlated with TD, mGCC, and cpRNFL thickness. In the normal hemifield, MBR was only correlated with mGCC thickness, and multiple regression analysis showed that mGCC thickness was a significant contributing factor of the MBR. Conclusion. MBR was well correlated with mGCC thickness in eyes with untreated NTG and a hemifield defect. In the normal hemifield, mGCC thickness was a contributing factor of the MBR indicating that ONH circulatory dysfunction may be associated with retinal structural changes in the early stages of glaucoma. A reduction in ONH microcirculation may be an early indicator of the presence and progression of glaucoma.

Longitudinal changes of ocular blood flow using laser speckle flowgraphy during normal pregnancy

PURPOSE

Innovative laser speckle flowgraphy (LSFG) enables noninvasive evaluation of retinal microcirculation and the usefulness has been reported in the field of ophthalmology. LSFG has allowed us to measure the real time changes of retinal blood flow without pupillary dilatations and contrast media. Herein, we investigated the change of retinal blood flow in normal pregnant women during gestation using LSFG.

METHODS

A prospective cohort study was conducted in 53 pregnant women who visited our institution between January, 2013 and July, 2014. Finally, a total of 41 participants without any obstetric complications were available for evaluation. Retinal blood flow was measured with LSFG in a total of 4 times during pregnancy (T1. 11-13 weeks, T2. 19-21 weeks, T3. 28-30 weeks, T4. 34-36 weeks) and mean blur rate (MBR), blowout score (BOS), flow acceleration index (FAI), and resistive index (RI) are analyzed from these measurements. Relations between LSFG parameters and mean arterial blood pressure (MAP) are determined throughout pregnancy.

RESULTS

MBR showed no significant changes throughout pregnancy. BOS showed a tendency to increase in the 3rd trimester. FAI values showed a slight increase from the 1st to 2nd trimester while a significant decrease was noted in the 3rd trimester. RI exhibited no changes between the 1st and 2nd trimesters, values decreased significantly after the 3rd trimester. MAP was positively correlated with BOS, and negatively correlated with FAI and RI.

CONCLUSION

The present study clearly demonstrated that profiles of LSFG parameters demonstrated a decrease of resistance in retinal blood vessels. These changes in indices provide a highly sensitive reflection of physiological changes in vascular resistance due to pregnancy. Thus, LSFG may be useful, as a non-invasive, diagnostic tool to detect pregnancy related disorders such as preeclampsia.

Relationships among Ocular Blood Flow Shown by Laser Speckle Flowgraphy, Retinal Arteriosclerotic Change, and Chorioretinal Circulation Time Obtained by Fluorescein Angiography

Purpose. To determine the correlations among the mean blur rate (MBR) in the optic nerve head (ONH) shown by laser speckle flowgraphy (LSFG), retinal arteriosclerosis, and the circulation time obtained by fluorescein angiography (FA). Method. We evaluated 118 patients and assessed their time of choroidal flush, arm-to-retina time, and early and late phases of retinal circulation time (RT: sec) obtained by FA. The severity of retinal arteriosclerosis was classified according to the Scheie classification. The MBR values throughout the ONH (MBR-A), in the tissue (MBR-T), and in the vessels (MBR-V) were analyzed. Results. Patients with retinal vein occlusion (RVO) showed prolonged early and late phases of RT compared to other ocular diseases. Single and multiple regression analyses showed that the MBR-V and Scheie classification were significantly associated with both the choroidal flush and arm-to-retina times. The incidences of RVO and MVR-V were significantly associated with the early phase of RT, and the incidences of RVO, MBR-V, Scheie classification, and gender were revealed to be factors independently contributing to the late phase of RT. Conclusion. MBR-V in the ONH and retinal arteriosclerosis are important contributing factors for the circulation time of each stage obtained by FA.

Evaluation of Fundus Blood Flow in Normal Individuals and Patients with Internal Carotid Artery Obstruction Using Laser Speckle Flowgraphy

Purpose

We investigated whether laser speckle flowgraphy (LSFG) results are comparable in both eyes and whether it is useful in the diagnosis of disparity in ocular ischemic syndrome (OIS) patients.

Methods

We compared the mean blur rate (MBR) value for various fundus regions in both eyes of 41 healthy subjects and 15 internal carotid artery occlusion (ICAO) cases. We calculated the standard value of the Laterality Index (LI), which was the MBR comparison of both eyes in each of the regions, in the control subjects. We then investigated the correlation between both eyes for the LIs in the entire fundus, the degree of ICAO and visual function.

Results

The disparity of the LIs in both eyes was least in the entire area of the fundus in control subjects and there was a significant correlation between both eyes of the 41 healthy individuals (P = 0.019). Significant correlations were found for the LI, visual acuity and degree of ICAO. The specificity and sensitivity of LI in the entire area was 93.8% and 100%, respectively.

Conclusions

LSFG revealed normal individuals have symmetrical fundus blood flow. LSFG could detect OIS and might be a useful tool for detecting disparities in fundus blood flow.

Relationship between Metabolic Syndrome and Ocular Microcirculation Shown by Laser Speckle Flowgraphy in a Hospital Setting Devoted to Sleep Apnea Syndrome Diagnostics

PURPOSE

To clarify whether the incidence of metabolic syndrome (MetS) and the overlap of MetS components are affecting the ocular circulation shown by laser speckle flowgraphy (LSFG).

MATERIALS AND METHODS

We studied 76 consistent patients. Blowout score (BOS) and blowout time (BOT), which are the pulse waveform analysis parameters, and mean blur rate (MBR) using LSFG in the optic nerve head (ONH) and choroid were evaluated. Throughout, the ONH was separated out from the vessels and tissue for analysis and MBRs in the ONH were divided into four sections (superior, temporal, inferior, and nasal).

RESULTS

Thirty-two patients were diagnosed having Mets. MBR-Tissue (P = 0.003), MBR-All (P = 0.01), MBR-Choroid (P = 0.04), and BOS-Choroid (P = 0.03) were significantly lower in patients with MetS than in the patients without MetS. Multiple-regression analysis revealed the temporal side of MBR-Tissue and BOS-Choroid which were identified as factors contributing independently to the overlap of the MetS components. Multiple-regression analysis also revealed that the MetS components were identified to be factors independently contributing to the BOS-Choroid and temporal side of MBR-Tissue.

CONCLUSION

Our study clarified that the incidence of MetS and the overlap of the MetS components are significantly affecting the ONH and choroidal microcirculation.

Arterial stiffness shown by the cardio-ankle vascular index is an important contributor to optic nerve head microcirculation

PROPOSE

The purpose of this study was to determine whether there were significant correlations between the pulse waveform in the capillary area of the optic nerve head (ONH) microcirculation shown by laser speckle flowgraphy (LSFG) and parameters of the systemic condition, especially the cardio-ankle vascular index (CAVI).

METHOD

We studied 130 men (ages 60.5 ± 10.9 years) who visited the Vascular Function Section of the Department of Cardiovascular Center of Toho University Sakura Medical Center. We evaluated the skew and blowout time (BOT) - which are parameters of pulse waveform analyses - using LSFG in the capillary area of the ONH for each patient. The CAVI, the E/e' ratio as the measure of diastolic left ventricular function, and the mean intima-media thickness (IMT) were evaluated as systemic parameters. We performed a Pearson's correlation analysis and a multiple regression analysis to determine independent factors for skew and BOT.

RESULTS

Heart rate, spherical refraction, and the CAVI (standard regression = 0.18, t = 2.61, p = 0.01) were revealed as factors contributing independently to the skew by multiple regression analysis. Heart rate, the CAVI (standard regression = -0.27, t = -3.92, p = 0.0002), the urinary albumin concentration, the mean IMT, spherical refraction, body mass index and pulse pressure were revealed as factors contributing independently to the BOT by multiple regression analysis.

CONCLUSION

The CAVI was demonstrated to be an independent factor contributing to both skew and BOT in the capillary area of the ONH. Our findings clarified that large arterial function shown by the CAVI contributes to smooth hemodynamics of microcirculation, shown by LSFG.

Effects of Exercise on the Structure and Circulation of Choroid in Normal Eyes

Aims

To determine the effects of dynamic exercise on the circulation and the luminal and stromal areas of the choroid in normal eyes.

Methods

This was a prospective interventional study of 38 eyes of 38 normal subjects enrolled by invitation. The systolic and diastolic blood pressures, heart rate, intraocularpressure, mean ocular perfusion pressure (MOPP), choroidal blood velocity, and enhanced depth imaging optical coherence tomographic (EDI-OCT) images were recorded before, and immediately after mild dynamic exercise. The same measurements were recorded after 10 min of rest. The choroidal blood velocity was measured bylaser speckle flowgraphy, and the mean blur rate was used for the evaluations. The horizontal EDI-OCT images of the subfoveal choroid were converted to binary images. The central choroidal thickness (CCT), total cross sectional choroidal area, luminal areas, stromal areas, and the ratio of luminal area to total choroidal area (L/C ratio) were determined from these images.

Results

The systolic and diastolic blood pressures, heart rate, MOPP, and the mean blur rate were significantly increased immediately after the exercise and significantly decreased 10 minutes after the exercise. There wereno significant changes in the mean CCT, the mean total choroidal area, the mean luminal and stromal areas, and the mean L/C ratio after the exercise.

Conclusions

Our results suggest that a rest period is needed before measurements of blood flow velocity but not necessary for the EDI-OCT imaging to determine the choroidal thickness and area.

The reduction of temporal optic nerve head microcirculation in autosomal dominant optic atrophy

PURPOSE

To evaluate the optic nerve head (ONH) microcirculation in autosomal dominant optic atrophy (ADOA) patients.

METHODS

This study comprised 22 eyes of 12 ADOA patients, diagnosed according to clinical findings including family history and the presence of mutations in the OPA1 gene. Twenty-four normal eyes of 24 age-matched subjects, with either the right or left eye randomly selected for use, served as controls. Circumpapillary retinal nerve fibre layer thickness (cpRNFLT) and mean blur rate (MBR) in the ONH were determined with optical coherence tomography (OCT) and laser speckle flowgraphy (LSFG), respectively. For each ONH quadrant (superior, temporal, inferior and nasal), the MBR and cpRNFLT ratio was also calculated by dividing tissue MBR in that quadrant by tissue MBR in the entire ONH and by dividing cpRNFLT in that quadrant by cpRNFLT in the entire ONH respectively.

RESULTS

Mean blur rate (MBR) in all quadrants was significantly lower in the ADOA patients than in the controls (p < 0.001 in each). The MBR ratio was significantly lower in the ADOA patients only in the temporal quadrant (p < 0.001). Similarly, cpRNFLT was lower in the ADOA patients in all quadrants (p < 0.001 in each), and the cpRNFLT ratio was lower in the temporal quadrant (p < 0.001).

CONCLUSION

Reduced blood flow in the temporal optic disc in ADOA patients is associated with reduced temporal cpRNFLT, suggesting that both are caused by damage to the papillomacular bundle. The anatomical characteristics of the papillomacular bundle may make it especially susceptible to mitochondrial dysfunction-induced damage, which occurs in ADOA.

The relationship between advanced glycation end products and ocular circulation in type 2 diabetes

AIMS

To determine whether skin autofluorescence (SAF) and serum pentosidine, biomarkers of advanced glycation end products (AGEs), were associated with ocular microcirculation in type 2 diabetes patients with early diabetic retinopathy (DR).

METHODS

This study included 46 eyes of 46 type 2 diabetes patients with no DR or non-proliferative DR. SAF was measured with an autofluorescence reader. Optic nerve head (ONH) microcirculation, represented by mean blur rate (MBR), was measured with laser speckle flowgraphy. Overall MBR, vascular MBR, and tissue MBR were calculated in software. MBR, SAF, pentosidine levels, and clinical findings, including central macular thickness (CMT), were then compared.

RESULTS

SAF in the diabetes patients was correlated with age (P=0.018). Serum pentosidine was correlated with age, vascular MBR and tissue MBR (P=0.046, P=0.035, and P=0.01, respectively). CMT was correlated with tissue MBR (P=0.016), but not with vascular MBR or overall MBR. Separate multiple regression analyses of independent contributing factors revealed that age, SAF, serum pentosidine, duration of diabetes, and pulse rate contributed to tissue MBR (P=0.041, P=0.046, P=0.022, P=0.011 and P=0.036, respectively), while SAF, HbA1c, pulse rate, tissue MBR, diastolic blood pressure, and creatinine contributed to CMT (P=0.005, P=0.039, P<0.001, P<0.001, P=0.022 and P=0.001, respectively).

CONCLUSIONS

Tissue MBR may be closely related to AGE levels and CMT in type 2 diabetes patients with early DR, suggesting that ocular circulation might be potential early biomarkers of DR.

Ocular blood flow values measured by laser speckle flowgraphy correlate with the postmenstrual age of normal neonates

PURPOSE

To evaluate the relationships between optic nerve head (ONH) blood flow by laser speckle flowgraphy (LSFG), and postmenstrual age and body weight in normal neonates.

METHODS

During their normal sleep, we studied 24 infants (postmenstrual age, 248-295 days) whose ocular blood flow could be measured three consecutive times. While the subjects slept in the supine position, three mean blur rate (MBR) values of the ONH were obtained: the MBR-A (mean of all values), MBR-V (vessel mean) and MBR-T (tissue mean) in the ONH. With regard to eye diseases, no retinopathy of prematurity (ROP) was observed, and no severe systemic diseases requiring treatment were noted in the subjects. Pearson's correlation coefficients were used to determine the relationship between the MBR-A, -V, -T and postmenstrual age (days) and body weight (g).

RESULTS

Postmenstrual age was significantly correlated with MBR-A (r = 0.64, p = 0.0007), MBR-V (r = 0.62, p = 0.0012) and MBR-T (r = 0.62, p = 0.0012). However, the body weight was not correlated with the MBR (MBR-A: r = 0.37, p = 0.07, MBR-V: r = 0.31, p = 0.14, MBR-T: r = 0.38, p = 0.06).

CONCLUSIONS

Our results clarified that the values of ocular blood flow measured by LSFG correlate with the postmenstrual age of normal neonates.

Relationship between glycosylated hemoglobin A1c and ocular circulation by laser speckle flowgraphy in patients with/without diabetes mellitus

PURPOSE

To determine whether there are significant correlations between the hemodynamics of the optic nerve head (ONH) and choroid as shown by laser speckle flowgraphy (LSFG) and the fasting blood sugar (FBS) and HbA1c level in patients with/without diabetes mellitus (DM).

METHODS

We analyzed 196 consecutive patients (151 men, 45 women). The pulse waveform analysis parameters of the mean blur rate (MBR), blowout score (BOS) and blowout time (BOT) in the ONH and choroid were evaluated. We used a multiple regression analysis to determine the independent factors for the LSFG parameters that are significantly correlated with FBS or HbA1c. We evaluated the relationship between the LSFG parameters FBS and HbA1c obtained from the 147 non-DM patients.

RESULTS

The multiple regression analysis revealed that hematocrit and HbA1c were factors contributing independently to the choroid MBR. The age, gender, pulse pressure, heart rate, spherical refraction and HbA1c were identified as factors contributing independently to the BOS in the ONH. The multiple regression analysis indicated that age, height, pulse pressure, heart rate and HbA1c were factors contributing independently to the BOS in the choroid. A Pearson's correlation analysis showed that the BOT values in the ONH and choroid were significantly correlated with the HbA1c in the non-DM patients.

CONCLUSION

Our results confirmed that HbA1c, even within the normal range, affected the blood flow in the ONH and choroid. LSFG may be a useful method to detect abnormalities of asymptomatic ocular circulation.

RETINAL BLOOD FLOW CORRELATES TO AQUEOUS VASCULAR ENDOTHELIAL GROWTH FACTOR IN CENTRAL RETINAL VEIN OCCLUSION

PURPOSE

As laser speckle flowgraphy can measure blood flow distribution in the ocular fundus, the authors analyzed the relationship between retinal blood flow and aqueous vascular endothelial growth factor (VEGF) concentration in central retinal vein occlusion.

METHODS

This prospective observational study examined 45 eyes of 45 patients with central retinal vein occlusion before treatment. Blood flow in large vessels around and at the optic disk, aqueous VEGF concentration, and arteriovenous passage time were examined. Blood flow was evaluated as mean blur rate by laser speckle flowgraphy.

RESULTS

Fluorescein angiography found 20 ischemic and 25 nonischemic type eyes. Aqueous VEGF concentration in the ischemic type was significantly higher than that in the nonischemic type (P = 0.01). Arteriovenous passage time was significantly correlated to the logarithm of the aqueous VEGF concentration (P = 0.0001). Mean blur rate of the affected eye/mean blur rate of the unaffected eye of the ischemic type was significantly lower than the nonischemic type (P = 0.039). Additionally, mean blur rate was significantly correlated both to the logarithm of the aqueous VEGF concentration (P < 0.0001) and to the arteriovenous passage time (P = 0.0001).

CONCLUSION

Laser speckle flowgraphy may be useful for predicting aqueous VEGF concentration and severity of central retinal vein occlusion.

Optic Nerve Head Blood Flow, as Measured by Laser Speckle Flowgraphy, Is Significantly Reduced in Preperimetric Glaucoma

PURPOSE

To compare optic nerve head (ONH) blood flow in healthy eyes, eyes with preperimetric glaucoma (PPG), and eyes with mild normal-tension glaucoma (NTG) using laser speckle flowgraphy (LSFG).

METHODS

In 172 eyes (normal: 44 eyes; PPG: 62 eyes; mild NTG: 66 eyes), LSFG was used to measure mean blur rate in the ONH tissue area (MBR_T), an index of capillary blood flow. Multiple regression analysis was performed to determine factors affecting circumpapillary retinal nerve fiber layer thickness (cpRNFLT), mean deviation (MD) and pattern standard deviation (PSD) of the visual field.

RESULTS

Despite similar characteristics in age, refractive error and systemic variables among the study groups, MBR_T in the normal eyes differed significantly from both the PPG and mild NTG eyes (P = 0.001, P < 0.001, respectively). Multiple regression analysis revealed that MBR_T was an independent factor affecting cpRNFLT, MD and PSD (P < 0.001, P = 0.001, P = 0.003, respectively).

CONCLUSION

ONH blood flow was detectibly reduced in eyes with PPG, in close association with structural and visual field damage. This suggests that measuring ONH tissue-area blood flow with LSFG may be a useful way of monitoring glaucoma severity, even in the early stages of glaucoma.

Application of Arterial Spin Labelling in the Assessment of Ocular Tissues

Arterial spin labelling (ASL) is a noninvasive magnetic resonance imaging (MRI) modality, capable of measuring blood perfusion without the use of a contrast agent. While ASL implementation for imaging the brain and monitoring cerebral blood flow has been reviewed in depth, the technique is yet to be widely used for ocular tissue imaging. The human retina is a very thin but highly stratified structure and it is also situated close to the surface of the body which is not ideal for MR imaging. Hence, the application of MR imaging and ASL in particular has been very challenging for ocular tissues and retina. That is despite the fact that almost all of retinal pathologies are accompanied by blood perfusion irregularities. In this review article, we have focused on the technical aspects of the ASL and their implications for its optimum adaptation for retinal blood perfusion monitoring. Retinal blood perfusion has been assessed through qualitative or invasive quantitative methods but the prospect of imaging flow using ASL would increase monitoring and assessment of retinal pathologies. The review provides details of ASL application in human ocular blood flow assessment.

Recent Clinical Applications of Laser Speckle Flowgraphy in Eyes with Retinal Disease

Retinal diseases related to ischemia, such as diabetic retinopathy, are the main cause of blindness worldwide. However, the pathogenesis of these diseases remains unclear, as does the time course of associated changes in ocular blood flow. Laser speckle flowgraphy (LSFG), which uses the laser speckle phenomenon to detect and quantify ocular circulation, is a promising candidate for a noninvasive method to measure ocular blood flow in living eyes. A recently developed LSFG measurement parameter, mean blur rate (MBR), can serve as a quantitative and reproducible index of retinal blood cell velocity. Mean blur rate can be used in the study of retinal diseases to evaluate microcirculation in the retinal vessels, choroid, and optic nerve head. In addition to overall MBR (MA), LSFG measurements of optic nerve head microcirculation can be divided into vessel-area MBR (MV) and tissue-area MBR (MT). Absolute values for MT have been shown to be linearly correlated with capillary blood flow, regardless of fundus pigmentation. Recently, there has been an increasing number of reports on the clinical applications of LSFG in retinal disease.

Pulse waveform analysis in the optic nerve head circulation reflects systemic vascular resistance obtained via a Swan-Ganz catheter

PURPOSE

To determine whether a pulse waveform analysis in the optic nerve head (ONH) circulation as determined by laser speckle flowgraphy (LSFG) can provide systemic hemodynamic values - the systemic vascular resistance (SVR) in particular - similar to those obtained by using a Swan-Ganz catheter, which is an invasive method.

METHOD

Sixteen consecutive subjects were examined. Hemodynamic monitoring was obtained from right heart catheterization with a Swan-Ganz catheter and coronary angiography without an intracoronary nitroglycerin administration. Direct blood pressure was measured with a trans-radial approach. Single regression analyses were used to determine the relationship between the blowout score and blowout time, which are the items of the pulse waveform analysis in the ONH, by using LSFG and the hemodynamic parameters.

RESULTS

The blowout time was significantly and negatively correlated with the SVR (r = -0.52, p = 0.04), the ocular perfusion pressure with the mean arterial blood pressure of the radial artery (r = -0.52, p = 0.04) and the radial artery pulse pressure (r = -0.52, p = 0.04).The pulmonary capillary wedge pressure (r  = -0.44, p = 0.09) and the mean arterial blood pressure of the radial artery (r  = -0.44, p = 0.09) tended to be correlated with the blowout time, but did not reach significance. The blowout score was significantly and negatively correlated with the radial artery blood pressure (r = -0.51, p = 0.046).

CONCLUSION

A pulse waveform analysis in the ONH by LSFG may be one of the useful methods for understanding the SVR.

Age- and Sex-Dependency of Laser Speckle Flowgraphy Measurements of Optic Nerve Vessel Microcirculation

Purpose

To investigate the relationship between various characteristics of a normal population and laser speckle flowgraphy (LSFG) measurements of mean blur rate (MBR) in the optic nerve head (ONH).

Methods

A total of 189 eyes of 189 normal subjects (93 male, 96 female, mean age 45 ± 14 years old, age range: 20–72) without any history of hypertension, hyperlipidemia or diabetes were enrolled. ONH microcirculation was measured with LSFG and overall MBR (MA), vessel-area MBR (MV), and tissue-area MBR (MT) were derived from these measurements. The statistical association of these measurements with characteristics such as sex, age, intraocular pressure (IOP) and systolic blood pressure (SBP) was then determined.

Results

There was a trend towards decreased IOP and MV and increased SBP with age (P = 0.002, P = 0.035, and P = 0.006, respectively). Furthermore, IOP, MV and SBP were correlated with age (r = -0.23, P = 0.011; r = -0.24, P < 0.001; and r = 0.30, P < 0.001, respectively). Separate multiple regression analyses of independent contributing factors revealed that sex and IOP contributed to MA (P < 0.001 and P = 0.002, respectively), sex, IOP, and age contributed to MV (P < 0.001, P = 0.003, and P = 0.024, respectively), while only IOP contributed to MT (P = 0.003).

Conclusion

In a normal population, MBR was affected by IOP in both the large vessel and capillary areas of the ONH, but not by SBP. MV was also affected by age and sex, while MT was stable independent of age or sex.

Ocular Blood Flow Measured Using Laser Speckle Flowgraphy During Aortic Arch Surgery With Antegrade Selective Cerebral Perfusion

OBJECTIVE

The objective of this study was to evaluate the validity of ocular blood flow measured using laser speckle flowgraphy (LSFG) for the assessment of cerebral perfusion during aortic arch surgery.

DESIGN

A prospective study.

SETTING

A single university hospital.

PARTICIPANTS

The study included 17 patients undergoing aortic arch surgery with cardiopulmonary bypass (CPB) using antegrade selective cerebral perfusion (ASCP).

INTERVENTIONS

Measurement of ocular blood flow using LSFG.

MEASUREMENTS AND MAIN RESULTS

Measurement of ocular perfusion that is supplied mainly from the ophthalmic artery might be useful as an indicator of cerebral blood flow because the ophthalmic artery is the first branch of the internal carotid artery. Recently, LSFG has been developed for noncontact estimation of ocular perfusion using the laser speckle phenomenon. In this study, the LSFG system was used to measure blood flow in the optic nerve head during aortic arch surgery with CPB using ASCP. The blood flow in the optic nerve head during ASCP was statistically significantly reduced by 40.6% compared with the baseline value after anesthetic induction.

CONCLUSIONS

Ocular blood flow measured using LSFG showed favorable validity for assessment of cerebral perfusion during aortic arch surgery with ASCP.

The association between systemic oxidative stress and ocular blood flow in patients with normal-tension glaucoma

PURPOSE

To evaluate the association between ocular blood flow and biomarkers of systemic oxidative stress, as well as the potential of these biomarkers to assess normal-tension glaucoma (NTG).

METHODS

This study included 73 eyes of 73 patients with NTG. We assessed ocular blood flow by measuring mean blur rate (MBR) in the optic nerve head using laser speckle flowgraphy, both overall and separately in the vessel and tissue areas. We also measured urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and skin autofluorescence (SAF), and lastly, determined correlations between these measurements and with other clinical parameters.

RESULTS

SAF was correlated with age, circumpapillary retinal nerve fiber layer thickness (cpRNFLT), mean deviation (MD), and overall MBR (P = 0.003, P = 0.013, P = 0.015 and P = 0.006, respectively). SAF and 8-OHdG were both correlated with tissue-area MBR (P = 0.006 and P = 0.010, respectively). Visual acuity, cpRNFLT, mean deviation and tissue-area MBR had a significant tendency to change with NTG severity (P = 0.014, P < 0.001, P < 0.001 and P = 0.006, respectively). Multiple regression analysis revealed that cpRNFLT and 8-OHdG were independent contributing factors to MD (P < 0.001 and P = 0.040, respectively), and that cpRNFLT and 8-OHdG were independent contributing factors to tissue-area MBR (P = 0.005 and P = 0.028, respectively).

CONCLUSIONS

We found a close relationship between cpRNFLT, MD, tissue MBR, SAF and 8-OHdG, suggesting that systemic oxidative stress is associated with decreased ocular blood flow and may be involved in the pathogenesis of NTG.

Reproducibility of Neonate Ocular Circulation Measurements Using Laser Speckle Flowgraphy

Measuring the ocular blood flow in neonates may clarify the relationships between eye diseases and ocular circulation abnormalities. However, no method for noninvasively measuring ocular circulation in neonates is established. We used laser speckle flowgraphy (LSFG) modified for neonates to measure their ocular circulation and investigated whether this method is reproducible. During their normal sleep, we studied 16 subjects (adjusted age of 34-48 weeks) whose blood flow could be measured three consecutive times. While the subjects slept in the supine position, three mean blur rate (MBR) values of the optic nerve head (ONH) were obtained: the MBR-A (mean of all values), MBR-V (vessel mean), and MBR-T (tissue mean), and nine blood flow pulse waveform parameters in the ONH were examined. We analyzed the coefficient of variation (COV) and the intraclass correlation coefficient (ICC) for each parameter. The COVs of the MBR values were all ≤ 10%. The ICCs of the MBR values were all >0.8. Good COVs were observed for the blowout score, blowout time, rising rate, falling rate, and acceleration time index. Although the measurement of ocular circulation in the neonates was difficult, our results exhibited reproducibility, suggesting that this method could be used in clinical research.

Relationship between plasma levels of vasoactive mediators and optic nerve head circulation shown by laser speckle flowgraphy

PROPOSE

To evaluate relationships between optic nerve head (ONH) circulation by laser speckle flowgraphy (LSFG), and secretion levels of plasma norepinephrine (NE), plasma renin activity (PRA), plasma aldosterone concentration (PAC), and plasma cortisol.

METHOD

Forty subjects were included in the study. The mean blur rates (MBR) throughout the ONH (MBR-all), in the tissue (MBR-tissue), and in vessels (MBR-vessel) were analyzed. In 29 subjects the following parameters were evaluated: plasma NE and ONH circulation in the evening and morning (Δ plasma NE, Δ MBR-all, -tissue, -vessel, and Δ area ratio of blood stream).

RESULTS

Plasma NE was significantly correlated with MBR-all (r = 0.39, P = 0.01) and MBR-vessel (r = 0.51, P = 0.0008). Plasma cortisol was significantly correlated with MBR-vessel (r =0.35, P = 0.03). The PRA (r = 0.31, P = 0.05) and PAC (r = 0.31, P = 0.05) tended to correlate with MBR-vessel. The multiple regression analysis revealed that plasma NE, PAC, and ocular perfusion pressure (OPP) were identified as factors contributing independently to the MBR-vessel (plasma NE: standard regression = 0.48, t-value = 3.12, P = 0.004; PAC: 0.43, 3.10, 0.04; OPP: 0.58, 2.34, 0.03, r = 0.71). Positive correlations between Δ plasma NE and Δ MBR-all (r = 0.46, P = 0.01), Δ MBR-tissue (0.38, 0.04), Δ MBR-vessel (0.41, 0.03), and Δ area ratio of blood stream (0.38, 0.04) were observed.

CONCLUSION

Our results clarified that the measurements of ONH circulation by LSFG is reflecting the plasma secretion levels of vasoactive mediators.

Pulse waveform analysis of optic nerve head circulation for predicting carotid atherosclerotic changes

PURPOSE

To evaluate the relationship between the parameters of pulse waveform analysis in the optic nerve head using laser speckle flowgraphy (LSFG) and intima-media thickness (IMT) and severity of carotid arterial plaque.

DESIGN

Prospective and cross-sectional study.

METHODS

One hundred seventy-six subjects were studied. Mean IMT and plaque score obtained from high-resolution B-mode ultrasound were evaluated. If mean IMT was 1 mm or greater, abnormal carotid artery thickening was diagnosed; if the plaque score exceeded 10, severe atherosclerosis was diagnosed. Blowout time and blowout score, which are parameters of pulse waveform analysis using LSFG, were evaluated. Logistic regression analyses determined the independent factors for abnormal carotid artery thickening and severe atherosclerosis. The cutoff levels for abnormal carotid artery thickening and severe atherosclerosis were analyzed using a conventional receiver operating characteristic (ROC) curve.

RESULTS

Logistic regression analysis showed that blowout time and body mass index contributed independently to abnormal carotid artery thickening, and blowout score contributed independently to severe atherosclerosis. The ROC curve showed that sensitivity and specificity of the blowout time and blowout score were equivalent to or greater than those of other factors. The cutoff level of the blowout time for abnormal carotid artery thickening was 46.4; the cutoff level of the blowout score for severe atherosclerosis was 71.8.

CONCLUSIONS

Measurement of blowout time and blowout score in the optic nerve head by LSFG can be useful for evaluating mean IMT and plaque score, which are parameters of carotid atherosclerosis.

Differences of Retinal Blood Flow Between Arteries and Veins Determined by Laser Speckle Flowgraphy in Healthy Subjects

To characterize the total retinal blood flow determined by laser speckle flowgraphy (LSFG) of healthy subjects.This prospective cross-sectional study was conducted at the Nagoya University Hospital. One hundred fifteen right eyes of 115 healthy subjects (mean age: 39.4 ± 16.1 years) were studied. The total blood flow in the retinal arteries and veins around the optic nerve head was measured separately using the total retinal flow index (TRFI), which represents blood flow volume. The lumen diameters of the retinal vessels determined by LSFG and by adaptive optics (AO) camera were compared. The images obtained by LSFG and AO camera were merged, and the distribution of the mean blur rates (MBRs), which represent the velocities of the erythrocytes, was evaluated on the images.The mean TRFI in veins (1812 ± 445, arbitral units) was significantly higher than that in arteries (1455 ± 348, arbitral units; P < 0.001). Linear regression analysis showed a significant correlation between the TRFI in the arteries and veins (P < 0.001). Linear regression analysis also showed a highly significant correlation between the diameters of arteries and veins determined by LSFG and by the AO camera (arteries, r = 0.94, P < 0.001; veins, r = 0.92, P < 0.001). The ratios of the lumen diameters determined by LSFG to that by AO camera was significant lower in arteries (0.068 ± 0.005, arbitral units) than in veins (0.074 ± 0.007, arbitral units) (P < 0.001). The MBRs of veins were homogeneous throughout the width of the lumen; however, the MBRs in the arteries were higher at the center and lower close to the walls of the lumen.The higher TRFIs in the veins than in the arteries indicate that there is a smaller volume of retinal blood flow in arteries than veins. However, the possibility remains that LSFG has inherent problem that the arterial lumen diameter determined by LSFG is smaller than actual one because of the characteristics of arteries. This would result in a smaller volume of retinal blood flow in the arteries than veins in LSFG.

Relationship of ocular microcirculation, measured by laser speckle flowgraphy, and silent brain infarction in primary aldosteronism

PURPOSE

Recent studies have shown that the risk of cerebro- and cardiovascular events (CVEs) is higher in patients with primary aldosteronism (PA) than in those with essential hypertension (EH), and that silent brain infarction (SBI) is a risk factor and predictor of CVEs. Here, we evaluated the relationship between findings from laser speckle flowgraphy (LSFG), a recently introduced non-invasive means of measuring mean blur rate (MBR), an important biomarker of ocular blood flow, and the occurrence of SBI in patients with PA.

METHODS

87 PA patients without symptomatic cerebral events (mean 55.1 ± 11.2 years old, 48 male and 39 female) were enrolled in this study. We measured MBR in the optic nerve head (ONH) with LSFG and checked the occurrence of SBI with magnetic resonance imaging. We examined three MBR waveform variables: skew, blowout score (BOS) and blowout time (BOT). We also recorded clinical findings, including age, blood pressure, and plasma aldosterone concentration.

RESULTS

PA patients with SBI (15 of 87 patients; 17%) were significantly older and had significantly lower BOT in the capillary area of the ONH than the patients without SBI (P = 0.02 and P = 0.03, respectively). Multiple logistic regression analysis revealed that age and BOT were independent factors for the presence of SBI in PA patients (OR, 1.15, 95% CI 1.01-1.38; P = .03 and OR, 0.73, 95% CI 0.45-0.99; P = .04, respectively).

CONCLUSION

PA patients with SBI were older and had lower MBR BOT than those without SBI. Our analysis showed that age was a risk factor for SBI, and that BOT was a protective factor, in patients with PA. This suggests that BOT, a non-invasive and objective biomarker, may be a useful predictor of SBI and form part of future PA evaluations and clinical decision-making.

Diurnal variations in blood flow at optic nerve head and choroid in healthy eyes: diurnal variations in blood flow

To investigate the diurnal variations of the ocular blood flow in healthy eyes using laser speckle flowgraphy (LSFG), and to determine the relationship of the diurnal variations between the ocular blood flow and other ocular parameters.This prospective cross-sectional study was conducted at Nagoya University Hospital. We studied 13 healthy volunteers whose mean age was 33.5 ± 7.6 years. The mean blur rate (MBR), expressing the relative blood flow, on the optic nerve head (ONH) and choroidal blood flow was determined by LSFG (LSFG-NAVI) every 3 hours from 6:00 to 24:00 hours. The intraocular pressure (IOP), choroidal thickness measured by enhanced depth imaging optical coherence tomography, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) in the brachial artery were also recorded. We evaluated the diurnal variations of the parameters and compared the MBR to the other parameters using a linear mixed model.The diurnal variations of the MBR on the ONH varied significantly with a trough at 9:00 hours and a peak at 24:00 hours (P < 0.001, linear mixed model). The MBR of choroid also had significant diurnal variations with a trough at 15:00 hours and a peak at 18:00 hours (P = 0.001). The IOP (P < 0.001), choroidal thickness (P < 0.001), SBP (P = 0.005), DBP (P = 0.001), and HR (P < 0.001) also had significant diurnal variations. Although the diurnal variation of the MBR on the ONH was different from the other parameters, that on the choroid was significantly and positively correlated with the DBP (P = 0.002), mean arterial pressure (P = 0.023), and mean ocular perfusion pressure (P = 0.047).We found significant diurnal variations in the ONH and choroidal blood flow. Although the ONH blood flow had its own diurnal variation because of strong autoregulation, the choroidal blood flow was more likely affected by systemic circulatory factors because of poor autoregulation.

The traditional kampo medicine tokishakuyakusan increases ocular blood flow in healthy subjects

The aim of this study was to examine the effects of oral administration of kampo medical formulas on ocular blood flow (OBF). A crossover protocol was used to randomly administer five grams of yokukansan, tokishakuyakusan (TSS), keishibukuryogan, or hachimijiogan to 13 healthy blinded subjects (mean age: 37.3 ± 12.3 years). The mean blur rate, a quantitative OBF index obtained with laser speckle flowgraphy, was measured at the optic nerve head before and 30 minutes after administration. Blood pressure (BP) and intraocular pressure (IOP) were also recorded. No significant changes were observed in mean BP or IOP after the administration of any of the kampo medical formulas. There was a significant increase in OBF 30 minutes after administration of TSS (100% to 103.6 ± 6.9%, P < 0.01). Next, TSS was administered to 19 healthy subjects (mean age: 32.0 ± 11.0 years) and OBF was measured before and 15, 30, 45, and 60 minutes after administration. Plain water was used as a control. OBF increased significantly after TSS administration compared to control (P < 0.01) and also increased from 30 to 60 minutes after administration compared to baseline (P < 0.05). These results suggest that TSS can increase OBF without affecting BP or IOP in healthy subjects.

Pulse-waveform analysis of normal population using laser speckle flowgraphy

PURPOSE

Laser speckle flowgraphy (LSFG), a new, non-invasive method of measuring the mean blur rate (MBR) of ocular blood flow, allows for the analysis of the pulse waveform of a heartbeat as it changes dynamically. Here, we investigated the relationship between the pulse waveform and clinical parameters, particularly age.

MATERIALS AND METHODS

Sixty eyes of 60 healthy subjects without diabetes were enrolled from among patients undergoing annual health examinations. LSFG, and its analysis software, were used to determine pulse waveform parameters including MBR, skew, blowout score (BOS), blowout time (BOT), rising rate and falling rate in the optic nerve head (ONH), both specifically in the tissue area and in the ONH overall. Fifteen clinical parameters were also recorded, including age and blood pressure, as well as triglyceride and creatinine levels.

RESULTS

Skew, BOT and falling rate had a strong correlation (|r| > 0.60) with age, but not with the other clinical parameters. This correlation with age was stronger in the tissue area (BOT: p < 0.0001, r = - 0.68; skew: p < 0.0001, r = 0.65; falling rate: p < 0.0001, r = 0.61) than in the ONH overall (BOT: p < 0.0001, r = -0.67; skew: p < 0.0001, r = 0.60; falling rate: p < 0.0001, r = 0.59). Stepwise multiple regression analysis revealed that tissue area falling rate was an independent factor indicating age, and conversely that age was an independent factor indicating tissue area falling rate.

CONCLUSIONS

The significant correlation of LSFG-measured tissue area falling rate with age suggests that it may be a new candidate biomarker for age-dependent microcirculation.

Ocular blood flow before, during, and after vitrectomy determined by laser speckle flowgraphy

BACKGROUND AND OBJECTIVE

Vitrectomy markedly alters the intraocular milieu, which can then affect the physiology of the retina and choroid. This study investigates whether vitrectomy also alters ocular blood flow as determined by laser speckle flowgraphy (LSFG).

PATIENTS AND METHODS

Twenty eyes of 20 patients that underwent vitrectomy for idiopathic macular hole or epiretinal membrane were studied. Standard 23-gauge microincision vitreous surgery was performed. Ocular blood flow of the optic nerve head, retinal vessels, and choroid was determined by LSGF before, during, and 2 weeks and 1 month after vitrectomy.

RESULTS

Postoperative blood flow of the optic nerve head, retinal vessels, and choroid did not differ significantly from preoperative values. Intraoperative blood flow of the optic nerve head and retinal vessels decreased significantly from baseline with increasing infusion pressure from 20 mm Hg to 40 mm Hg (P < .01), and choroidal blood flow decreased significantly when the infusion pressure increased from 8 mm Hg to 20 mm Hg and from 20 mm Hg to 40 mm Hg (both P < .01).

CONCLUSION

Blood flow did not differ significantly postoperatively versus preoperatively, but it was significantly reduced during vitrectomy with increasing infusion pressure. Careful attention should be paid to infusion pressure during vitrectomy.

The influence of posture change on ocular blood flow in normal subjects, measured by laser speckle flowgraphy

PURPOSE

To investigate, using laser speckle flowgraphy (LSFG), the autoregulation of ocular blood flow (BF) in response to posture change.

METHODS

This study comprised 20 healthy volunteers (mean age 30.0 ± 8.5). The mean blur rate (MBR) of the ocular circulation in the subjects was assessed in both a sitting and a supine position every 2 min over the course of 10 min. Baseline measurements of the MBR at the optic nerve head (ONH) and the choroid were taken in a sitting position. Increases in the MBR ratio in a supine position were calculated with reference to this baseline. Intraocular pressure (IOP), systemic blood pressure and heart rate in the brachial artery were also recorded.

RESULTS

In the ONH, the MBR ratio increased significantly over the baseline after 2 min (104.8 ± 5.0%, p = 0.001) and 4 min (104.4 ± 5.6%, p = 0.005), in a supine position, but decreased to the initial level after only 6 min. In the choroid, on the other hand, while the MBR ratio also increased significantly after 2 min in a supine position (113.7 ± 8.1%, p < 0.001), it kept this significant increase over the time course of 10 min. After 10 min in a supine position, IOP increased significantly (p < 0.001), systolic blood pressure decreased significantly (p < 0.001), but diastolic blood pressure did not change significantly compared to the baseline. (p = 0.07) CONCLUSIONS: ONH and choroidal circulation have significantly different hemodynamics in response to posture change in healthy volunteers. This finding suggests that LSFG enables us to assess the autoregulation of BF in the ONH.

Pulse-Wave Analysis of Optic Nerve Head Circulation Is Significantly Correlated with Kidney Function in Patients with and without Chronic Kidney Disease

Aim. To determine whether there is a significant correlation between the optic nerve head (ONH) circulation determined by laser speckle flowgraphy (LSFG) and kidney function. Materials. Seventy-one subjects were investigated. The estimated glomerular filtration rate (GFR) and serum creatinine, cystatin C, and urinary albumin excretion were measured. The ONH circulation was determined by an analysis of the pulse wave of LSFG, and this parameter was named blowout time (BOT). Chronic kidney disease (CKD) was defined to be present when the estimated GFR was <60 mL/min per 1.73 m². Pearson's correlation coefficients were used to determine the relationship between the BOT and the kidney function. We also examined whether there were significant differences in all parameters in patients with and without CKD. Results. BOT was significantly correlated with the level of creatinine (r = −0.24, P = 0.04), the estimated GFR (r = 0.42, P = 0.0003), cystatin C (r = −0.29, P = 0.01), and urinary albumin excretion (r = −0.29, P = 0.01). The BOT level in subjects with CKD was significantly lower than that in subjects without CKD (P = 0.002). Conclusion. BOT in ONH by LSFG can detect the organ damage such as kidney dysfunction, CKD.

Spatial versus temporal laser speckle contrast analyses in the presence of static optical scatterers

Previously published data demonstrate that the temporal processing algorithm for laser speckle contrast imaging (LSCI) can improve the visibility of deep blood vessels and is less susceptible to static speckle artifacts when compared with the spatial algorithm. To the best of our knowledge, the extent to which the temporal algorithm can accurately predict the speckle contrast associated with flow in deep blood vessels has not been quantified. Here, we employed two phantom systems and imaging setups (epi-illumination and transillumination) to study the contrast predicted by the spatial and temporal algorithms in subsurface capillary tubes as a function of the camera exposure time and the actual flow speed. Our data with both imaging setups suggest that the contrast predicted by the temporal algorithm, and therefore the relative flow speed, is nearly independent of the degree of static optical scattering that contributes to the overall measured speckle pattern. Collectively, these results strongly suggest the potential of temporal LSCI at a single-exposure time to assess accurately the changes in blood flow even in the presence of substantial static optical scattering.

Analysis of choroidal morphologic features and vasculature in healthy eyes using spectral-domain optical coherence tomography

OBJECTIVE

To analyze the morphologic features and vasculature of the choroid in healthy eyes using spectral-domain (SD) optical coherence tomography (OCT).

DESIGN

Cross-sectional retrospective review.

PARTICIPANTS

Forty-two healthy subjects (42 eyes) with no ocular disease who underwent high-definition scanning with Cirrus high-definition OCT (Carl Zeiss Meditec, Inc., Dublin, CA) at the New England Eye Center, Boston, Massachusetts, between November 2009 and September 2010.

METHODS

The SD OCT images were evaluated for morphologic features of the choroid, including the shape of the choroid-scleral border, location of the thickest point of choroid, and regions of focal choroidal thinning. Total choroidal thickness and large choroidal vessel layer thickness were measured by 2 independent observers experienced in analyzing OCT images using the Cirrus linear measurement tool at the fovea, 750 μm nasal and temporal to the fovea. Custom software was used to calculate the ratio of choroidal stroma to the choroidal vessel lumen.

MAIN OUTCOME MEASURES

Qualitative assessment of the choroidal morphologic features, quantitative analysis of choroidal vasculature, and use of novel automated software to determine the ratio of choroidal stromal area to the area of choroidal vessel lumen.

RESULTS

The 42 subjects had a mean age of 51.6 years. All subjects (100%) had a so-called bowl or convex shape to the choroid-sclera junction, and the thickest point of the choroid was under the fovea in 88.0% of the subjects. The mean choroidal thickness was 256.8 ± 75.8 μm, mean thickness of the large choroidal vessel layer was 204.3 ± 65.9 μm, and that of the medium choroidal vessel layer-choriocapillaris layer was 52.9 ± 20.6 μm beneath the fovea. The ratio of large choroidal vessel layer thickness to the total choroidal thickness beneath the fovea was 0.7 ± 0.06. The software-generated ratio of choroidal stromal area to the choroidal vessel lumen area was 0.27 ± 0.08, suggesting that choroidal vessel lumen forms a greater proportion of the choroid than the choroidal stroma in healthy eyes.

CONCLUSIONS

This is the first study to describe the morphologic features and vasculature of the choroid in healthy eyes from 1-line raster scans obtained using SD OCT. The method described holds promise and has immediate clinical usefulness in recognizing subtle changes in choroidal morphologic features and the role of choroidal angiopathy in various disease states that, in the future, may inform new treatment methods.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Comparison of CCD-equipped laser speckle flowgraphy with hydrogen gas clearance method in the measurement of optic nerve head microcirculation in rabbits

The aim of this study was to verify the correlation between mean blur rate (MBR) obtained with CCD-equipped laser speckle flowgraphy (LSFG) and capillary blood flow (CBF) obtained by the hydrogen gas clearance method in rabbit optic nerve head (ONH). Using Japanese white rabbits under systemic anesthesia, a hydrogen electrode was inserted an area of the ONH free from superficial capillaries. MBR was measured with LSFG near the hydrogen electrode. CBF and MBR were measured in the range of 32.4-83.5 mL/min/100 g and 3.5-6.0, respectively. MBR and CBF were significantly correlated (r = 0.73, P < 0.01, n = 14). After inhalation of carbon dioxide (CO(2)) or intravenous administration of endothelin-1 (ET-1), MBR and CBF were changed in the relative range of 0.74-1.27 and 0.76-1.35, respectively. The relative changes in MBR and CBF induced by CO(2) and ET-1 were also significantly correlated (r = 0.67, P < 0.01). The current results suggest that MBR may correlate with CBF and also change with CBF, as an index of blood flow in the ONH, linearly.

Optic nerve head circulation determined by pulse wave analysis is significantly correlated with cardio ankle vascular index, left ventricular diastolic function, and age

AIM

To determine whether there is a significant correlation between optic nerve head circulation determined by pulse wave analysis of laser speckle flowgraphy (LSFG), and the cardio-ankle vascular index (CAVI), left ventricular (LV) function, and age.

METHODS

Forty-nine men who visited the Vascular Function Section of Toho University Sakura Medical Center, Chiba, Japan were studied. The mean age of the subjects was 60.7±10.6 years (range 29 to 80 years). The CAVI, left ventricular ejection fraction (LVEF) as a function of the systolic LV function, early diastolic mitral annulus velocity (e'), and the ratio of transmitral early peak velocity (E) to e' (E/e' ratio) as the diastolic LV function, and the optic nerve head circulation determined by pulse wave analysis of the LSFG. This parameter was named the blowout time (BOT).

RESULTS

The BOT was significantly correlated with age, heart rate, body mass index (BMI), triglyceride, LVEF, e' velocity, E/e' ratio, and CAVI. The results of multiple regression analysis showed that age was significantly associated with CAVI (r= 0.36, p=0.002), BOT (r=-0.30, p=0.01) and e' velocity (r=-0.21, p=0.04).

CONCLUSIONS

The BOT of the optic nerve head circulation determined by LSFG was significantly correlated with age but was independent of cardiac diastolic function and arterial stiffness. This suggests that the damage to different organs increases with age. Our results confirmed that BOT can be helpful in evaluating physiological aging of the microcirculation.

Pulse-wave analysis of optic nerve head circulation is significantly correlated with brachial-ankle pulse-wave velocity, carotid intima-media thickness, and age

BACKGROUND

To determine whether there is a significant correlation between the pulse-wave analysis in the optic nerve head circulation determined by laser speckle flowgraphy (LSFG), and brachial-ankle pulse wave velocity (baPVW), carotid intima-media thickness (IMT), and age.

METHODS

Thirty-three patients who visited the Vascular Function Section in our hospital were included. Age was 57.3 ± 12.6 years, with a range from 29 to 80 years. baPVW, carotid IMT, and pulse wave analysis in optic nerve head circulation using LSFG were conducted on subjects, and this parameter is named blowout time (BOT). The following items were analyzed as other systemic parameters: age, blood pressure, pulse pressure, heart rate, body mass index, and mean arterial blood pressure; other ocular parameters were intraocular pressure and ocular perfusion pressure. Pearson's correlation coefficients were used to determine the relationship between the BOT, baPWV, IMT, age, and other parameters. In addition, multiple regression analysis was used to determine independent factors for age.

RESULTS

BOT was significantly correlated with age (r = -0.85, P <0.0001), pulse pressure (r = -0.36, P = 0.04), baPWV (r = -0.72, P <0.0001), and IMT (r = -0.64, P < 0.0001). The result of multiple regression analysis showed that baPWV (odds ratio = 0.93, 95% confidence interval = 0.03-1.82 P = 0.04) and BOT (-2.26, -3.27 to -1.26, <0.0001) were independent contribution factors to age.

CONCLUSIONS

Our results confirmed measurements of BOT in the optic nerve head can be a useful method for determinin g whether early atherosclerotic changes are present in the optic nerve head circulation.

Significant correlations between optic nerve head microcirculation and visual field defects and nerve fiber layer loss in glaucoma patients with myopic glaucomatous disk

BACKGROUND

Eyes with glaucoma are characterized by optic neuropathy with visual field defects in the areas corresponding to the optic disk damage. The exact cause for the glaucomatous optic neuropathy has not been determined. Myopia has been shown to be a risk factor for glaucoma. The purpose of this study was to determine whether a significant correlation existed between the microcirculation of the optic disk and the visual field defects and the retinal nerve fiber layer thickness (RNFLT) in glaucoma patients with myopic optic disks.

METHODS

Sixty eyes of 60 patients with myopic disks were studied; 36 eyes with glaucoma (men:women = 19:17) and 24 eyes with no ocular diseases (men:women = 14:10). The mean deviation (MD) determined by the Humphrey field analyzer, and the peripapillary RNFLT determined by the Stratus-OCT were compared between the two groups. The ocular circulation was determined by laser speckle flowgraphy (LSFG), and the mean blur rate (MBR) was compared between the two groups. The correlations between the RNFLT and MBR of the corresponding areas of the optic disk and between MD and MBR of the optic disk in the glaucoma group were determined by simple regression analyses.

RESULTS

The average MBR for the entire optic disk was significantly lower in the glaucoma group than that in the control group. The differences of the MBR for the tissue in the superior, inferior, and temporal quadrants of the optic disk between the two groups were significant. The MBR for the entire optic disk was significantly correlated with the MD (r = 0.58, P = 0.0002) and the average RNFLT (r = 0.53, P = 0.0008). The tissue MBR of the optic disk was significantly correlated with the RNFLT in the superior, inferior, and temporal quadrants.

CONCLUSIONS

Our study suggests that there is a causal relationship between the thinner RNFLT that led to the MD and reduction in the microcirculation in the optic nerve head.