Use of colour Doppler imaging in ocular blood flow research

Central retinal artery occlusion or retinal stroke: a neurosonologist's perspective

In central retinal artery occlusion (CRAO) or retinal stroke, which is usually a vision-threatening condition, timely diagnosis is imperative to improve the chances of retinal preservation and to establish adequate secondary prevention measures. Even though retinal strokes have been traditionally assigned to the field of ophthalmology, while considering reperfusion therapy as the only way to avoid permanent vision loss, we suggest prompt evaluation of CRAO causes (primarily related to cardiovascular risk factors) performed by a well-organized interdisciplinary team (ophthalmologist and neurologist) in a neurovascular center with stroke expertise. Therefore, the most suitable adjunct method for rapidly diagnosing non-arteritic CRAO could be target transorbital ultrasound, performed by an experienced neurologist/neurosonologist in the stroke unit. Consequently, after an ophthalmological assessment, a final decision on thrombolytic therapy could be made. We accept that further research is obviously needed to determine whether transorbital ultrasound could replace ophthalmological investigation in the case of a suspected acute retinal stroke. We assert that retinal stroke requires interdisciplinary treatment in cooperation with neurologists and ophthalmologists, with an additive value for each to achieve the best results for the patient.

Vascular imaging findings in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a vascular disease among preterm infants involving incomplete or abnormal retinal vascularization and is a leading cause of preventable blindness globally. Measurements of ocular blood flow originating from a variety of imaging modalities, including colour Doppler imaging (CDI), fluorescein angiography (FA) and ocular coherence tomography angiography (OCTA), have been associated with changes in ROP patients. Herein, we discuss and summarize the relevant current literature on vascular imaging and ROP reviewed through December 2022. Differences in vascular imaging parameters between ROP patients and healthy controls are reviewed and summarized. The available data identify significantly increased peak systolic velocity (PSV) in the central retinal artery and ophthalmic artery as measured by CDI, increased vascular tortuosity as measured by FA, smaller foveal avascular zone (FAZ) as measured by FA and OCTA, and increased foveal vessel density (VD) and reduced parafoveal VD as measured by OCTA in ROP patients compared with controls. None of the above findings appear to reliably correlate with visual acuity. The studies currently available, however, are inconclusive and lack robust longitudinal data. Vascular imaging demonstrates the potential to aid in the diagnosis, management and monitoring of ROP, alongside retinal examination via indirect ophthalmoscopy and fundus photography.

Development of an Artificial Soft Solid Gel Using Gelatin Material for High-Quality Ultrasound Diagnosis

For ultrasound diagnosis, a gel is applied to the skin. Ultrasound gel serves to block air exposure and match impedance between the skin and the probe, enhancing imaging efficiency. However, if use of the ultrasound gel exceeds a certain period of time, it may dry out and be exposed to air, causing impedance mismatch and reducing imaging resolution. In such cases, the use of a soft, solid gel proves advantageous, as it can be employed for an extended period without succumbing to the drying phenomenon and can be reused after disinfection. Its soft consistency ensures excellent skin adhesion. Our soft solid gel demonstrated approximately 1.2 times better performance than water, silicone, and traditional ultrasound gels. When comparing the dimensions of grayscale, dead zone, vertical, and horizontal regions, the measurements for the traditional ultrasound gel were 93.79 mm, 45.32 mm, 103.13 mm, 83.86 mm, and 83.86 mm, respectively. In contrast, the proposed soft solid gel exhibited dimensions of 105.64 mm, 34.48 mm, 141.1 mm, and 102.8 mm.

The Relationship between Transcranial Doppler Ultrasonography and Visual Field Test Results in Glaucoma and Glaucoma Suspect Patients

PURPOSE

To evaluate the relationships between parameters of transcranial ultrasonography and results of visual field tests in patients with open angle glaucoma or suspected of having glaucoma.

METHODS

This retrospective study was based on data from medical records of patients who visited the Department of Ophthalmology in Kangbuk Samsung Hospital from January 1, 2016, to October 17, 2019, and underwent transcranial Doppler ultrasonography as part of a routine health examination. Ophthalmic data were visual acuity, intraocular pressure, optical coherence tomography, and Humphrey visual field test results. Retinal nerve fiber layer defect was confirmed by a glaucoma specialist. Patients' ophthalmic data, such as average ganglion cell layer thickness, visual field index, pattern standard deviation, and mean deviation, were divided into quartiles. Each ophthalmic artery parameter from transcranial Doppler ultrasonography was compared between quartiles.

RESULTS

A total of 162 patients were reviewed. There was no difference in Doppler ophthalmic artery (OA) parameters between patients with or without retinal nerve fiber layer defect. None of the quartile groups of average ganglion cell layer thickness showed significant difference in any OA parameters. Patients in the low-visual field index quartile showed significant low peak systolic velocities of OAs when adjusted for age, sex, and presence of diabetes mellitus or hypertension (p = 0.016). A higher pattern standard deviation showed lower peak systolic velocity (p = 0.046). There was no significant tendency between any other OA parameter and mean deviation value.

CONCLUSIONS

Our study suggests that hemodynamic parameters of ophthalmic arteries might be associated with visual field status of patients. Further large-population studies are needed in order to better understand the relationship between visual function and ocular blood flow.

The Role of Color Doppler Imaging in the Diagnosis of Glaucoma: A Review of the Literature

Glaucoma is a progressive optic neuropathy and one of the leading causes of irreversible blindness worldwide. Elevated intraocular pressure (IOP) is the major risk factor for the onset and progression of glaucoma. In addition to elevated IOP, impaired intraocular blood flow is also considered to be involved in the pathogenesis of glaucoma. Various techniques have been used to assess ocular blood flow (OBF), including Color Doppler Imaging (CDI), a technique used in ophthalmology in recent decades. This article reviews the role of CDI in both the diagnosis and effective monitoring of glaucoma progression, presenting the protocol for imaging and its advantages, as well as the limitations of its use. Moreover, it analyzes the pathophysiology of glaucoma, focusing on vascular theory and its role in the onset and progression of the disease.

The impact of obesity on ocular hemodynamics and choroidal thickness

Background

Obesity affects microvascular structures. The effect of obesity on the ocular vascular system can be evaluated by changes in the choroidal thickness (CT) and retrobulbar blood flow (RBF).

Objectives

To evaluate the CT and RBF parameters in obese patients with various body mass index (BMI) values and compare these parameters with normal weight, healthy subjects.

Design

A prospective study.

Methods

The study included 102 eyes of 102 female patients. Patients were divided into three groups according to BMI as group 1 with a BMI of 18.5-24.99 (n = 32), normal weight group; group 2 with a BMI of 30-34.99 (n = 35), as obese class I; and group 3 with a BMI of 35-39.99 (n = 35), as obese class II. The peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index, and pulsatility index values of the central retinal artery (CRA) and ophthalmic artery (OA) were evaluated with color Doppler ultrasonography. CT was measured at the subfoveal area and at 500-µm intervals nasal and temporal to the fovea up to a distance of 1500 µm by using the enhanced depth imaging technique of optical coherence tomography. Intraocular pressure (IOP) was measured with a Goldmann applanation tonometry.

Results

There was a significant difference in IOP values within the groups with the highest values in group 3 (17.6 ± 2.1 mmHg) and the lowest in group 1 (12.4 ± 1.7 mmHg). The CT in groups 2 and 3 was found to be statistically significantly lower than that in group 1 at all measurement points (p < 0.001). There was a statistically significant negative correlation between CT at all measurement points and BMI (p < 0.001). The mean CRA PSV, EDV, and OA EDV values were statistically significantly lower in each obese group than those values in group 1 (p < 0.001). The OA PSV values were significantly lower in group 3 (36.5 ± 5.9 cm/s) than those in group 2 (43.8 ± 4 cm/s) and group 1 (44.6 ± 5.2 cm/s) (p < 0.001). Also, significant associations were found between BMI and CRA PSV, CRA EDV, and OA PSV values (p < 0.001).

Conclusion

Obesity may predispose to eye pathologies by changing the ocular vascular circulation.

Ophthalmic artery changes in type 2 diabetes with and without acute coronary syndrome

Background

Ocular blood flow provides a new perspective for studying the effects of diabetes and ischemic heart disease on systemic blood flow, pathological mechanisms, and prognosis. Previous studies have analyzed the hemodynamic changes of the ophthalmic artery (OA) in patients with diabetes and ischemic heart disease, but the results remain controversial due to limited observation methods. We aimed to explore the morphological and hemodynamic features in the OA in patients with type 2 diabetes (T2D) with and without acute coronary syndrome (ACS).

Methods

In total, 134 participants, including 30 control participants, 34 with ACS only, 34 with T2D only, and 36 with both ACS and T2D, undergoing computed tomography angiography were enrolled. Three-dimensional OA models were reconstructed, and morphological parameters of the OA were measured. In addition, numerical simulations using computational fluid dynamics were used to acquire hemodynamic parameters of the OA.

Results

In this study, 134 OA models were reconstructed. Morphological measurements revealed a smaller initial OA diameter in the T2D group than in the other two ACS groups. A hemodynamic simulation showed a significantly lower OA blood velocity in patients with ACS and T2D than that in controls (P < 0.001). The mass flow ratios in all disease groups were lower than those in the control group (P < 0.001, P = 0.020, and P < 0.001, respectively). The ACS and T2D groups had higher OA pressure levels than those of the control group (P = 0.013). The OA blood velocity and mass flow ratio were correlated with several clinical parameters.

Conclusions

This study revealed morphological and hemodynamic differences in the OA between patients with T2D with and without ACS. Furthermore, the hemodynamic characteristics of the OA correlated with clinical prognostic biomarkers, suggesting the potential predictive ability of the OA.

Correlation between retinal oxygen saturation and the haemodynamic parameters of the ophthalmic artery in healthy subjects

PURPOSE

The aim of the study was to obtain the values of oxygen saturation in retinal vessels and ophthalmic blood flow parameters in a healthy Caucasian population and assess whether the oximetry parameters are affected by the flow rate or the vascular resistance.

METHODS

The spectrophotometric retinal oximetry and colour Doppler imaging (CDI) of retinal vessels were successfully performed with 52 healthy subjects (average age 29.7 ± 5.6 years). The retinal oximeter simultaneously measures the wavelength difference of haemoglobin oxygen saturation in retinal arterioles and venules. The arteriolar and venular saturation in both eyes was measured. The peak systolic (PSV) end diastolic (EDV) velocities, resistive (RI) and pulsatility (PI) indices were obtained for both eyes using CDI in the ophthalmic artery. A paired t-test and two sample t-tests were used for statistical analyses. The correlation was assessed using the Pearson coefficient correlation.

RESULTS

The mean oxygen saturation level was 96.9 ± 3.0% for the retinal arterioles and 65.0 ± 5.1% for the retinal venules. The A-V difference was 31.8 ± 4.6%. The mean of the measured haemodynamic parameters was PSV 46.6 ± 9.4 cm/s, EDV 12.0 ± 3.5 cm/s, PI 1.68 ± 0.38 and RI 0.74 ± 0.05. No significant difference in oxygen saturation and haemodynamic parameters was found between the left and the right eyes or the dominant and non-dominant eye. The oximetry and ultrasound values were sex independent. The Pearson correlation coefficient demonstrated a significant yet weak negative correlation between A-V difference and RI (r = -0.321, p = 0.020).

CONCLUSIONS

A negative correlation between A-V difference and resistance index was observed, suggesting that reduced oxygen consumption may reflect the increased vascular tone of the ophthalmic vessels, which is likely determined by autoregulatory mechanisms.

Numerical and Experimental Analysis of Shear Stress Influence on Cellular Viability in Serpentine Vascular Channels

3D bioprinting has emerged as a tool for developing in vitro tissue models for studying disease progression and drug development. The objective of the current study was to evaluate the influence of flow driven shear stress on the viability of cultured cells inside the luminal wall of a serpentine network. Fluid-structure interaction was modeled using COMSOL Multiphysics for representing the elasticity of the serpentine wall. Experimental analysis of the serpentine model was performed on the basis of a desirable inlet flow boundary condition for which the most homogeneously distributed wall shear stress had been obtained from numerical study. A blend of Gelatin-methacryloyl (GelMA) and PEGDA200 PhotoInk was used as a bioink for printing the serpentine network, while facilitating cell growth within the pores of the gelatin substrate. Human umbilical vein endothelial cells were seeded into the channels of the network to simulate the blood vessels. A Live-Dead assay was performed over a period of 14 days to observe the cellular viability in the printed vascular channels. It was observed that cell viability increases when the seeded cells were exposed to the evenly distributed shear stresses at an input flow rate of 4.62 mm/min of the culture media, similar to that predicted in the numerical model with the same inlet boundary condition. It leads to recruitment of a large number of focal adhesion point nodes on cellular membrane, emphasizing the influence of such phenomena on promoting cellular morphologies.

Elevated endothelin-1 levels as risk factor for an impaired ocular blood flow measured by OCT-A in glaucoma

The purpose of this study was to ascertain whether a correlation exists between glaucoma-associated alteration of ocular vascular haemodynamics and endothelin-1 (ET-1) levels exist. Eyes of patients with cataract (n = 30) or glaucoma (n = 68) were examined with optical coherence tomography (OCT) and OCT-angiography (OCT-A; AngioVue™-RTVue-XR; Optovue, Fremont, California, USA). The peripapillary and the macular vessel density (VD) values were measured. Inferior and superior retinal nerve fibre layer (RNFL) thickness loss was used for further OCT staging. Aqueous humour of the examined eye and plasma were sampled during cataract or glaucoma surgery and analysed by means of ELISA to determine their ET-1 level. Glaucoma eyes are characterised by reductions in RNFL thickness and VD that correlate significantly with the OCT GSS score. Peripheral and ocular ET-1 level were significantly elevated in patients with glaucoma and correlate positively with the OCT-GSS score of the entire study population. Peripapillary and macula VD of glaucoma patients correlates negatively with plasma ET-1 levels. Multivariable analysis showed a subordinate role of intraocular pressure predictive factor for impaired retinal blood flow compared with plasma ET-1 level in glaucoma. Peripheral ET-1 level serves as risk factor for detection of ocular blood flow changes in the optic nerve head region of glaucomatous eyes.

Ocular Ultrasound: Review of Bioeffects and Safety, Including Fetal and Point of Care Perspective: Review of Bioeffects and Safety, Including Fetal and Point-of-Care Perspective

Ocular ultrasound is an invaluable tool for the evaluation of the eye and orbit. However, the eye and orbit are potentially sensitive to the thermal and mechanical effects of ultrasound. When performing B-mode imaging, dedicated ocular settings should be used. If these settings are not available, limiting the acoustic output to Food and Drug Administration (FDA) recommended maximum levels is strongly advised. Especially important is the acoustic output in spectral (pulsed) and color Doppler modes, which can exceed the FDA's maximum recommended levels for the eye. Adjusting settings to decrease acoustic output and limiting the time of the examination should be done when performing a Doppler examination. The acoustic output of shear wave elastography is significantly higher than FDA guidelines for the eye and should be considered experimental.

Hemodynamic and morphological changes of the central retinal artery in myopic eyes

Due to excessive elongation of the eyeball, myopia-related vascular abnormalities are frequently observed in the central retinal artery (CRA) and its intraretinal branches. In addition to inconsistency in previously reported findings, hemodynamic (reduced flow velocity, increased vascular resistance) and morphological changes (narrower vessel diameter) were usually studied separately. This cross-sectional study evaluated the hemodynamic and morphological characteristics concurrently in a large sample of healthy myopes, by using the color Doppler ultrasound and adaptive optics retinal camera. Results showed that the retrobulbar segment of CRA had a tendency of slightly reduced flow velocity in eyeballs with longer axial length, but the correlation was not significant after adjusting for the multiple correlations. Vascular resistance was not affected by the axial elongation. With respect to the intraretinal branches, no significant changes in longer eyes of total diameter or lumen diameter were observed, while both the wall thickness and the wall cross-sectional area were significantly increased, but only a marginally increase in the wall to lumen ratio was found with increasing axial length. This implies some potential small artery remodeling in the intraretinal CRA branches. Overall, blood supply of the inner retina in healthy young myopes is likely to be maintained. Additionally, morphological parameters of vascular microstructure could be potential biomarkers to monitor myopia progression and understand myopia-related vascular abnormalities in future studies.

Ophthalmic Artery Morphological and Hemodynamic Features in Acute Coronary Syndrome

Purpose

To examine the morphological and hemodynamic changes of the ophthalmic artery (OA) in patients with acute coronary syndrome (ACS).

Methods

This cross-sectional observational study included 31 patients with ACS and 10 healthy controls (HCs). The ACS subgroups were ST-segment elevation myocardial infarction (STEMI; n = 10), non-STEMI (n = 10), and unstable angina (n = 11). OA three-dimensional (3D) models were reconstructed based on computed tomographic angiography, and morphological aspects of the OA were measured quantitatively. Moreover, numerical simulation by computational fluid dynamics was used to obtain hemodynamic information of the OA.

Results

The study reconstructed 41 OA models. Hemodynamic simulation revealed a significant decrease in OA blood velocity in patients with ACS compared with the HCs (median velocity, 0.046 vs. 0.147 m/s; P < 0.001). No differences in the morphological data for the OA were observed. Also, no differences in the mass flow ratio of OA to the ipsilateral internal carotid artery was found. Similar differences were observed between the ACS subgroups and HCs. OA blood velocity was negatively correlated with body mass index, abdominal circumference, left ventricular ejection fraction, and triacylglycerol and was positively correlated with early to late transmitral flow velocity, N-terminal pro-brain natriuretic peptide, serum creatinine, and potassium.

Conclusions

The initial OA blood velocity was slower in patients with ACS and was associated with ACS-related clinical parameters. To our knowledge, this is the first study to analyze OA characteristics in ACS using 3D model reconstruction and hemodynamic simulation, providing new perspectives on the relationship between ischemic heart disease and ocular manifestations.

Structural and haemodynamic properties of ocular vasculature in axial myopia

The high prevalence of myopia has become a global concern, especially in East and Southeast Asia. Alarmingly, the prevalence of high myopia is increasing. Mechanical stretching caused by excessive eyeball elongation leads to various anatomical changes in the fundus. This stretching force may also lead to the development of vascular abnormalities, which tend to be subtle and easily overlooked. A healthy ocular vasculature is a prerequisite of adequate oxygen supply for normal retinal functions. This review summarises previous findings on structural and haemodynamic aspects of myopia-related vascular changes.

Feasibility of MRI to assess differences in ophthalmic artery blood flow rate in normal tension glaucoma and healthy controls

Purpose

To examine feasibility of phase‐contrast magnetic resonance imaging (PCMRI) and to assess blood flow rate in the ophthalmic artery (OA) in patients with normal tension glaucoma (NTG) compared with healthy controls.

Methods

Sixteen patients with treated NTG and 16 age‐ and sex‐matched healthy controls underwent PCMRI using a 3‐Tesla scanner and ophthalmological examinations. OA blood flow rate was measured using a 2D PCMRI sequence with a spatial resolution of 0.35 mm².

Results

The blood flow rate in the NTG group was 9.6 ± 3.9 ml/min [mean ± SD] compared with 11.9 ± 4.8 ml/min in the control group. Resistance Index (RI) and Pulsatility Index (PI) were 0.73 ± 0.08 and 1.36 ± 0.29, respectively, in the NTG group and 0.68 ± 0.13 and 1.22 ± 0.40, respectively, in the healthy group. The mean visual field index (VFI) was 46% ± 25 for the worse NTG eyes. The measured differences observed between the NTG group and the control group in blood flow rate (p = 0.12), RI (p = 0.18) and PI (p = 0.27) were non‐significant.

Conclusions

This case–control study, using PCMRI, showed a slight, but non‐significant, reduction in OA blood flow rate in the NTG patients compared with the healthy controls. These results indicate that blood flow may be of importance in the pathogenesis of NTG. Considering that only a limited portion of the total OA blood flow supplies the ocular system and the large inter‐individual differences, a larger study or more advanced PCMRI technique might give the answer.

Correlation between retrobulbar blood flow parameters and retinal nerve fiber, ganglion cell and inner plexus layer thickness in myopia

PURPOSE

To assess the thickness of the retinal nerve fiber layer (RNFL), ganglion cell and inner plexus layer (GCIPL) and blood flow parameters in retrobulbar vessels, and to analyze correlations between these parameters in myopes.

METHODS

The study included forty myopic and 20 healthy eyes. Standard eye examination was supplemented with OCT of the optic nerve and macula (GCIPL, RNFL, RNFL in each quadrant and rim area of the optic nerve) and color Doppler imaging of retrobulbar arteries [peak systolic and end-diastolic velocities, pulsatile index and resistance index (RI) in the ophthalmic (OA), central retinal (CRA), nasal posterior ciliary and temporal posterior ciliary arteries].

RESULTS

Significant correlations were found between blood flow parameters in the CRA, RNFL and GCIPL thickness, and axial length (AL) and spherical equivalent (SE). There were significant positive correlations between RNFL with PSV and EDV in the CRA and negative correlations between RNFL and RI in the CRA. GCIPL was positively correlated with PSV and EDV in the CRA. The decrease in RA was associated with reduced blood flow velocities in the CRA, TPCA and NPCA.

CONCLUSION

The reduced retrobulbar blood flow in healthy young myopes is correlated with increasing AL and refractive value, and thinning of the RNFL and GCIPL. Reduction of the rim-area of the optic disc is associated with vascular and retinal circulatory disorders. These phenomena indicate the vascular basis of the described changes. To the best of our knowledge, this is the first study which correlates ocular circulation with retinal structure.

Usefulness of point-of-care ultrasound for the evaluation of non-traumatic eye emergencies

The role of clinical ultrasound or Point-of-Care Ultrasound (POCUS) in patients with urgent pathology has expanded exponentially in recent years. With clinical ultrasound, physicians can make a quick assessment and decide how to act in time critical situations. Ocular ultrasound is one of the most recently developed applications. In patients with severe non-traumatic ocular pathology it has numerous clinically relevant uses: retinal detachment, occlusion of the central retinal artery or optic nerve pathologies, among others. The technique is widely available, easy to perform, and can provide information even when fundoscopy is impossible. In this review, we describe the bases of clinical ocular ultrasound, focusing on the management of the main non-traumatic urgent ophthalmological pathologies that the physician may face in their clinical practice.

Dorzolamide/Timolol Fixed Combination: Learning from the Past and Looking Toward the Future

The key clinical attributes of preserved dorzolamide/timolol fixed combination (DTFC) and the emerging potential of preservative-free (PF) DTFC are reviewed with published evidence and clinical experience. The indications and role of DTFC in current glaucoma management are critically discussed. Preserved DTFC became the first intraocular pressure (IOP)-lowering fixed combination (FC) approved by the US Food and Drug Administration (FDA) and remains one of most commonly used medications worldwide. The pharmacological properties of DTFC reflect those of its two time-tested constituents, i.e., the carbonic anhydrase inhibitor dorzolamide and the non-selective beta-blocker timolol. In regulatory studies DTFC lowers IOP on average by 9 mmHg (32.7%) at peak and by 7.7 mmHg (27%) at trough. In trials DTFC shows equivalence to unfixed concomitant therapy, but in real-life practice it may prove superior owing to enhanced convenience, elimination of the washout effect from the second drop, improved tolerability, and better adherence. PF DTFC became the first PF FC approved, first in unit-dose pipettes, and more recently in a multidose format. Cumulative evidence has confirmed that PF DTFC is at least equivalent in efficacy to preserved DTFC and provides a tangible clinical benefit to patients with glaucoma suffering from ocular surface disease by improving tolerability and adherence. Finally, we identify areas that warrant further investigation with preserved and PF DTFC

Effects of age on the peak ratio of ophthalmic artery Doppler

This study aimed to investigate the effects of age on the peak ratio (PR) of ophthalmic artery (OA) Doppler.The initial peak velocity (P1), second peak velocity (P2) and PR of OA were detected by color Doppler ultrasonography in 147 healthy subjects. All of the subjects were divided into 6 groups (G1-G6) according to the age. (G1, 20-29 years; G2, 30-39 years; G3, 40-49 years; G4, 50-59 years; G5, 60-69 years; and G6, 70 years or older). The blood pressure and heart rate were also examined before ultrasonography. The influences of age, blood pressure and heart rate on the P1, P2, and PR were further evaluated.There were significant differences in the P2 and PR among different age groups except for P1. There were no significant differences in the P2 and PR between the first 2 groups, neither among the latter 4 groups. Nevertheless, P2 and PR in the first 2 groups were significantly different from those in the latter 4 groups. In addition, both P2 and PR (not P1) increased significantly with age, systolic and diastolic blood pressure. P1, P2 and PR were not related to heart rate. Both P2 and PR were closely related to the age. PR also had a weak relationship with systolic blood pressure.Both P2 and PR of OA Doppler increase with age. Concern should be raised when P2 and PR are used to evaluate the hemodynamic change of OA.

OCTA Multilayer and Multisector Peripapillary Microvascular Modeling for Diagnosing and Staging of Glaucoma

Purpose

To develop and assess an automatic procedure for classifying and staging glaucomatous vascular damage based on optical coherence tomography angiography (OCTA) imaging.

Methods

OCTA scans (Zeiss Cirrus 5000 HD-OCT) from a random eye of 39 healthy subjects and 82 glaucoma patients were used to develop a new classification algorithm based on multilayer and multisector information. The averaged circumpapillary retinal nerve fiber layer (RNFL) thickness was also collected. Three models, support vector machine (SVM), random forest (RF), and gradient boosting (xGB), were developed and optimized for classifying between healthy and glaucoma patients, primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG), and glaucoma severity groups.

Results

All the models, the SVM (area under the receiver operating characteristic [AUROC] 0.89 ± 0.06), the RF (AUROC 0.86 ± 0.06), and the xGB (AUROC 0.85 ± 0.07), with 26, 22, and 29 vascular features obtained after feature selection, respectively, presented a similar performance to the RNFL thickness (AUROC 0.85± 0.06) in classifying healthy and glaucoma patients. The superficial vascular plexus was the most informative layer with the infero temporal sector as the most discriminative region of interest. No significant differentiation was obtained in discriminating the POAG from the NTG group. The xGB model, after feature selection, presented the best performance in classifying the severity groups (AUROC 0.76± 0.06), outperforming the RNFL (AUROC 0.67± 0.06).

Conclusions

OCTA multilayer and multisector information has similar performance to RNFL for glaucoma diagnosis, but it has an added value for glaucoma severity classification, showing promising results for staging glaucoma progression.

Translational Relevance

OCTA, in its current stage, has the potential to be used in clinical practice as a complementary imaging technique in glaucoma management.

Predictive value of ophthalmic artery Doppler velocimetry in relation to hypertensive disorders of pregnancy

PURPOSE

To test the predictive value of ophthalmic artery (OA) Doppler velocimetry in relation to the occurrence of hypertensive disorders of pregnancy (HDP).

METHODS

We compared, by analysis of variance, the values of seven OA Doppler variables (peak systolic velocity, second systolic peak velocity [P2], mean velocity, end diastolic velocity, resistance index [RI], pulsatility index [PI], and peak ratio) of 31 women with preeclampsia and 33 women with gestational hypertension vs those of 227 women without HDP. The prognostic value of these variables in relation to the occurrence of HDP was evaluated by the area under the curve (AUC) receiver operating characteristic curve.

RESULTS

All OA Doppler variables except RI and PI showed significant (P < .5) differences between groups. After adjustment for confounders, only P2 was an independent predictor of HDP (P < .001), with an AUC of 0.76. The best cut-off point for predicting HDP was P2 ≥ 21.4 cm/s, with sensitivity 69%, specificity 78%, positive likelihood ratio 3.1, negative likelihood ratio 0.4, positive predictive value 47%, and negative predictive value 90%. P2 improved the predictive ability of a model based on clinical variables, incrementing AUC from 0.77 to 0.84 in the final model containing clinical and Doppler variables.

CONCLUSION

The elevation of OA P2 in the second trimester of pregnancy is an independent predictor of hypertensive disorders, and improves the discriminatory ability of clinical markers.

Microvascular damage assessed by optical coherence tomography angiography for glaucoma diagnosis: a systematic review of the most discriminative regions

A growing number of studies have reported a link between vascular damage and glaucoma based on optical coherence tomography angiography (OCTA) imaging. This multitude of studies focused on different regions of interest (ROIs) which offers the possibility to draw conclusions on the most discriminative locations to diagnose glaucoma. The objective of this work was to review and analyse the discriminative capacity of vascular density, retrieved from different ROIs, on differentiating healthy subjects from glaucoma patients. PubMed was used to perform a systematic review on the analysis of glaucomatous vascular damage using OCTA. All studies up to 21 April 2019 were considered. The ROIs were analysed by region (macula, optic disc and peripapillary region), layer (superficial and deep capillary plexus, avascular, whole retina, choriocapillaris and choroid) and sector (according to the Garway-Heath map). The area under receiver operator characteristic curve (AUROC) and the statistical difference (p-value) were used to report the importance of each ROI for diagnosing glaucoma. From 96 screened studies, 43 were eligible for this review. Overall, the peripapillary region showed to be the most discriminative region with the highest mean AUROC (0.80 ± 0.09). An improvement of the AUROC from this region is observed when a sectorial analysis is performed, with the highest AUROCs obtained at the inferior and superior sectors of the superficial capillary plexus in the peripapillary region (0.86 ± 0.03 and 0.87 ± 0.10, respectively). The presented work shows that glaucomatous vascular damage can be assessed using OCTA, and its added value as a complementary feature for glaucoma diagnosis depends on the region of interest. A sectorial analysis of the superficial layer at the peripapillary region is preferable for assessing glaucomatous vascular damage.

Ophthalmic artery resistance index after peribulbar block in the presence of epinephrine

PURPOSE

There are controversies regarding ophthalmic artery (OA) flow after peribulbar block in the presence of epinephrine. Therefore, we aimed to evaluate OA flow via echo-Doppler before and after peribulbar block with lidocaine in the presence or absence of epinephrine.

METHODS

Fifty-six patients who had an American Society of Anesthesiologists (ASA) classification of I, II or III and were eligible for cataract phacoemulsification surgery were selected. Patients with other eye diseases were excluded. Patients were divided into two groups: group 1-peribulbar block with lidocaine and 1/200,000 epinephrine; group 2-peribulbar block with lidocaine in the absence of epinephrine. The resistance index (RI), peak systolic velocity (PSV), end diastolic velocity (EDV) of the OA were evaluated using echo-Doppler before and 10 min after the peribulbar block.

RESULTS

No differences between groups were observed in the RI before the peribulbar block as well regarding the presence of hypertension and the age or gender of the patient. After the peribulbar block, we observed a decrease in the RI in group 1 (p = 0.038, Cohen's d = 0.336) and no difference in the RI in group 2 (p = 0.109, Cohen's d = 0.172). When comparing group 1 and group 2, we observed a decrease in the RI in group 1 (p = 0.028, Cohen's d = 0,583). There was no difference between groups regarding the PSV and EDV after the peribulbar block.

CONCLUSIONS

A decrease in RI was observed in the OA after peribulbar block with a vasoconstrictor, an effect that could be a benefit in some ocular surgeries.

Assessment of Doppler flow parameters of the retrobulbar arteries and internal carotid artery in patients with glaucoma: the significance of ophthalmic artery peak ratio and the intima-media thickness of the internal carotid artery

PURPOSE

The objective of this study was to analyze flow parameters of the central retinal artery (CRA), ophthalmic artery (OA), and internal carotid artery (ICA) assessed by color Doppler ultrasound.

METHODS

Thirty-five patients with primary open-angle glaucoma (PAAG), 65 patients with normal-tension glaucoma (NTG), and 45 healthy controls, a total of 145 patients were included in this study and study participants were divided into three groups. All study participants underwent color Doppler ultrasound to assess blood flow parameters of CRA, OA and ICA.

RESULTS

Comparisons among three groups revealed that pulsatility index and resistive index of the OA were significantly higher and peak ratio and end-systolic volume were significantly lower in patients with NTG or PAAG compared to healthy controls (p < 0.001 for all). As with OA, resistive index of the CRA was statistically significantly higher in patients with glaucoma (PAAG and NTG) compared to healthy controls (p < 0.001). The peak systolic volume and intima-media thickness of the ICA were statistically significantly higher in patients with PAAG compared to the other two groups (p < 0.001). ROC curve analysis of the CRA resistive index, OA resistive index and OA peak ratio in patients with glaucoma (PAAG and NTG) revealed that the sensitivity and specificity were 89% and 88%; 86% and 84%; 84% and 82%, respectively, at cutoff values of 0.64, 0.78 and 0.59, respectively.

CONCLUSIONS

Ophthalmic artery peak ratio and ICA intima-media thickness may be useful parameters in the diagnosis of patients with glaucoma.

Evaluation of Diurnal Fluctuation in Parafoveal and Peripapillary Vascular Density Using Optical Coherence Tomography Angiography in Patients with Exfoliative Glaucoma and Primary Open-Angle Glaucoma

PURPOSE

To determine the diurnal variations in parafoveal and peripapillary vessel density using optical coherence tomography angiography in patients with exfoliative glaucoma, patients with primary open-angle glaucoma and healthy individuals.

MATERIALS AND METHODS

In this prospective cross-sectional study, 36 exfoliative glaucoma patients, 34 primary open-angle glaucoma patients and 35 healthy individuals were examined. Optical coherence tomography angiography was used for examining the vessel density of peripapillary (radial peripapillary capillary) and parafoveal (superficial layer) regions. Optical coherence tomography angiography readings were obtained at 09:00, 11:00, 14:00 and 16:00 on the same day. Intraocular pressure values were assessed accordingly. The intraclass correlation coefficients were used to evaluate test-retest variability.

RESULTS

Diurnal variation in intraocular pressure or vessel density values was not found in any parafoveal or peripapillary region in any of the groups at any hour of measurement. The vessel density in the temporal sector of the exfoliative glaucoma group was significantly lower than in the primary open-angle glaucoma group at all time points. (Mann-Whitney U test; 09:00, P= .015; 11:00, P= .002; 14:00, P= .040; and 16:00, P= .048, respectively). The test-retest repeatability was high and almost excellent for the parafoveal and peripapillary regions in each group (XFG range: 0.757 - 0.985, POAG range: 0.834 - 0.985, and control range: 0.708 - 0.983).

CONCLUSIONS

It may be important to estimate the diurnal fluctuation occurring in retinal haemodynamics in patients with exfoliative glaucoma and primary open-angle glaucoma despite the lack of any considerable variation in intraocular pressure and retinal vessel density values in one day. The study found that at any point of time, vessel density of radial peripapillary capillary in temporal region was lower in exfoliative glaucoma patients than in primary open-angle glaucoma patients having the same glaucoma severity.

The Relationship between Ocular Vascular Changes and the Levels of Malondialdehyde and Vascular Endothelial Growth Factor in Patients with Inflammatory Bowel Disease

Background: We evaluated ocular hemodynamic changes, malondialdehyde(MDA) and vascular endothelial growth factor (VEGF) levels in patients with IBD.Methods: We used ocular color Doppler ultrasonography to analyze 56 eyes with Crohn's disease (CD), 62 eyes with ulcerative colitis (UC), 68 eyes of healthy volunteers. We measured peak systolic velocity (PSV),end-diastolic velocity (EDV),and the resistivity index (RI) of ophthalmic artery (OA) and central retinal artery (CRA). MDA and VEGF levels were measured in the plasma samples.Results: MDA levels were significantly higher in both UC and CD patients, whereas VEGF levels were only higher in the CD group (p = .003,p < .001,p = .01).The PSV and EDV of the OA were significantly lower in CD patients (p = .017,p = .001). The EDV of the CRA was significantly lower in CD patients than UC patients and controls (p = .014,p < .001).Conclusions: CD patients exhibited decreased blood flow in both the OA and CRA. Ocular vascular flow was only affected in CD patients. We found that ocular ischemia may occur in CD patients even in the absence of any clinical finding.

Ocular blood flow as a clinical observation: Value, limitations and data analysis

Alterations in ocular blood flow have been identified as important risk factors for the onset and progression of numerous diseases of the eye. In particular, several population-based and longitudinal-based studies have provided compelling evidence of hemodynamic biomarkers as independent risk factors for ocular disease throughout several different geographic regions. Despite this evidence, the relative contribution of blood flow to ocular physiology and pathology in synergy with other risk factors and comorbidities (e.g., age, gender, race, diabetes and hypertension) remains uncertain. There is currently no gold standard for assessing all relevant vascular beds in the eye, and the heterogeneous vascular biomarkers derived from multiple ocular imaging technologies are non-interchangeable and difficult to interpret as a whole. As a result of these disease complexities and imaging limitations, standard statistical methods often yield inconsistent results across studies and are unable to quantify or explain a patient's overall risk for ocular disease. Combining mathematical modeling with artificial intelligence holds great promise for advancing data analysis in ophthalmology and enabling individualized risk assessment from diverse, multi-input clinical and demographic biomarkers. Mechanism-driven mathematical modeling makes virtual laboratories available to investigate pathogenic mechanisms, advance diagnostic ability and improve disease management. Artificial intelligence provides a novel method for utilizing a vast amount of data from a wide range of patient types to diagnose and monitor ocular disease. This article reviews the state of the art and major unanswered questions related to ocular vascular anatomy and physiology, ocular imaging techniques, clinical findings in glaucoma and other eye diseases, and mechanistic modeling predictions, while laying a path for integrating clinical observations with mathematical models and artificial intelligence. Viable alternatives for integrated data analysis are proposed that aim to overcome the limitations of standard statistical approaches and enable individually tailored precision medicine in ophthalmology.

Microvascular contributions to age-related macular degeneration (AMD): from mechanisms of choriocapillaris aging to novel interventions

Aging of the microcirculatory network plays a central role in the pathogenesis of a wide range of age-related diseases, from heart failure to Alzheimer's disease. In the eye, changes in the choroid and choroidal microcirculation (choriocapillaris) also occur with age, and these changes can play a critical role in the pathogenesis of age-related macular degeneration (AMD). In order to develop novel treatments for amelioration of choriocapillaris aging and prevention of AMD, it is essential to understand the cellular and functional changes that occur in the choroid and choriocapillaris during aging. In this review, recent advances in in vivo analysis of choroidal structure and function in AMD patients and patients at risk for AMD are discussed. The pathophysiological roles of fundamental cellular and molecular mechanisms of aging including oxidative stress, mitochondrial dysfunction, and impaired resistance to molecular stressors in the choriocapillaris are also considered in terms of their contribution to the pathogenesis of AMD. The pathogenic roles of cardiovascular risk factors that exacerbate microvascular aging processes, such as smoking, hypertension, and obesity as they relate to AMD and choroid and choriocapillaris changes in patients with these cardiovascular risk factors, are also discussed. Finally, future directions and opportunities to develop novel interventions to prevent/delay AMD by targeting fundamental cellular and molecular aging processes are presented.

Age-related changes in retrobulbar circulation: a literature review

Introduction

The advances in research methods used in ophthalmology allow for an increasingly accurate examination of the eyes, as well as the morphology and function of the vessels. Colour Doppler imaging is still the first-line method for the analysis of parameters of retrobulbar circulation. Therefore, the aim of this work was to present the current state of knowledge about anatomical and functional age-related changes in retrobulbar arteries.

Methods

A literature search was performed mainly based on the PubMed database.

Results

The anatomy of retrobulbar arteries, histological background of age-related vascular changes, age-related changes in retrobulbar blood flow in the ophthalmic artery, central retinal artery, short posterior ciliary arteries, and the reference values for the age-dependent retrobulbar circulation parameters measured by colour Doppler imaging are discussed in this review.

Conclusion

The age of the subject should always be taken into account when interpreting the parameters of retrobulbar blood flow measured by colour Doppler imaging.

Guidelines for ultrasound examination in ophthalmology. Part III: Color Doppler ultrasonography

The aim of this article was to present the possibilities of use and application of color-coded Doppler ultrasonography in the diagnosis of various diseases of the eyeball and orbit which result from vascular disorders. Color-coded Doppler ultrasonography is recommended for the assessment of blood flow velocity in the retrobulbar arteries. That is why the article contains current recommendations for Doppler imaging in ophthalmology. The paper provides detailed recommendations for patient's preparation for the examination, presents the scanning technique and safety of the examination, and lists ophthalmological diseases of vascular origin for which color-coded Doppler ultrasonography can be applied. Furthermore, the article also presents other techniques applied in clinical practice for the assessment of blood flow or imaging of vasculature of a given eyeball structure, inter alia: power Doppler ultrasonography, 3D and 4D ultrasonography, magnetic resonance angiography, spiral computer tomography, transcranial ultrasonography and modern microvascular imaging. The authors emphasize the usefulness of color-coded Doppler ultrasonography in the diagnosis of diseases which result from blood flow disorders within the eyeball, such as amaurosis fugax, ocular ischemic syndrome, insufficiency in vessels supplying the carotid and vertebral arteries, posterior ischemic optic neuropathy, glaucoma, age-related macular degeneration, vascular vision disorders, vascular malformations, such as arteriovenous fistula, orbital varices, systemic connective tissue diseases in retinopathy of prematurity, diabetes, thyroid disorders or strabismus. The application of color-coded Doppler ultrasonography is especially important in the assessment of the vasculature of intrabulbar tumorous lesions and in the differential diagnosis of intrabulbar tumors.

The aim of this article was to present the possibilities of use and application of color-coded Doppler ultrasonography in the diagnosis of various diseases of the eyeball and orbit which result from vascular disorders. Color-coded Doppler ultrasonography is recommended for the assessment of blood flow velocity in the retrobulbar arteries. That is why the article contains current recommendations for Doppler imaging in ophthalmology. The paper provides detailed recommendations for patient’s preparation for the examination, presents the scanning technique and safety of the examination, and lists ophthalmological diseases of vascular origin for which color-coded Doppler ultrasonography can be applied. Furthermore, the article also presents other techniques applied in clinical practice for the assessment of blood flow or imaging of vasculature of a given eyeball structure, inter alia: power Doppler ultrasonography, 3D and 4D ultrasonography, magnetic resonance angiography, spiral computer tomography, transcranial ultrasonography and modern microvascular imaging. The authors emphasize the usefulness of color-coded Doppler ultrasonography in the diagnosis of diseases which result from blood flow disorders within the eyeball, such as amaurosis fugax, ocular ischemic syndrome, insufficiency in vessels supplying the carotid and vertebral arteries, posterior ischemic optic neuropathy, glaucoma, age-related macular degeneration, vascular vision disorders, vascular malformations, such as arteriovenous fistula, orbital varices, systemic connective tissue diseases in retinopathy of prematurity, diabetes, thyroid disorders or strabismus. The application of color-coded Doppler ultrasonography is especially important in the assessment of the vasculature of intrabulbar tumorous lesions and in the differential diagnosis of intrabulbar tumors.

A Protocol to Evaluate Retinal Vascular Response Using Optical Coherence Tomography Angiography

Introduction

Optical coherence tomography angiography (OCT-A) is a novel diagnostic tool with increasing applications in ophthalmology clinics that provides non-invasive high-resolution imaging of the retinal microvasculature. Our aim is to report in detail an experimental protocol for analyzing both vasodilatory and vasoconstriction retinal vascular responses with the available OCT-A technology.

Methods

A commercial OCT-A device was used (AngioVue^®, Optovue, CA, United States), and all examinations were performed by an experienced technician using the standard protocol for macular examination. Two standardized tests were applied: (i) the hypoxia challenge test (HCT) and (ii) the handgrip test, in order to induce a vasodilatory and vasoconstriction response, respectively. OCT-A was performed at baseline conditions and during the stress test. Macular parafoveal vessel density of the superficial and deep plexuses was assessed from the en face angiograms. Statistical analysis was performed using STATA v14.1 and p < 0.05 was considered for statistical significance.

Results

Twenty-four eyes of 24 healthy subjects (10 male) were studied. Mean age was 31.8 ± 8.2 years (range, 18–57 years). Mean parafoveal vessel density in the superficial plexus increased from 54.7 ± 2.6 in baseline conditions to 56.0 ± 2.0 in hypoxia (p < 0.01). Mean parafoveal vessel density in the deep plexuses also increased, from 60.4 ± 2.2 at baseline to 61.5 ± 2.1 during hypoxia (p < 0.01). The OCT-A during the handgrip test revealed a decrease in vessel density in both superficial (55.5 ± 2.6 to 53.7 ± 2.9, p < 0.001) and deep (60.2 ± 1.8 to 56.7 ± 2.8, p < 0.001) parafoveal plexuses.

Discussion

In this work, we detail a simple, non-invasive, safe, and non-costly protocol to assess a central nervous system vascular response (i.e., the retinal circulation) using OCT-A technology. A vasodilatory response and a vasoconstriction response were observed in two physiologic conditions—mild hypoxia and isometric exercise, respectively. This protocol constitutes a new way of studying retinal vascular changes that may be applied in health and disease of multiple medical fields.

Color Doppler imaging in thyroid eye disease and its correlation to disease activity

Purpose: To evaluate alterations in orbital color Doppler imaging (CDI) parameters and their correlation to disease activity and severity in patients with thyroid eye disease (TED). Methods: Seventy-six orbits of 45 TED patients and 40 orbits of 40 normal controls were enrolled in this cross-sectional study. According to clinical activity score (CAS), patients were categorized to active (CAS ≥ 3) or inactive disease (CAS < 3). Patients were also classified as having mild, moderate or severe disease. Peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) in ophthalmic artery and central retinal artery, and maximum and minimum velocity in superior ophthalmic vein and central retinal vein were determined in all subjects. Results: There was a significant difference in maximum velocity of superior ophthalmic vein and EDV and RI of ophthalmic artery between patients with TED and normal subjects. Superior ophthalmic vein maximum and minimum velocity and ophthalmic artery RI were significantly higher in patients with active disease than inactive cases. Disease severity did not affect the blood flow parameters independently. A cutoff point of 3.99 cm/s in superior ophthalmic vein maximum velocity yielded a sensitivity of 91.2% and specificity of 81.2% in detecting active disease. Conclusion: Retrobulbar blood flow is altered in TED and is related to disease activity. Superior ophthalmic vein maximum velocity could be helpful in differentiation of active and inactive cases.

Ocular Hemodynamics in Acute Nonarteritic Anterior Ischemic Optic Neuropathy Compared With Normal Tension Glaucoma

PURPOSE

The purpose of this study was to evaluate ocular hemodynamics in patients with a disease believed to be related to a chronic vascular damage [ie, normal tension glaucoma (NTG)] in comparison with an entity with an acute ischemic impact on the optic nerve [ie, acute nonarteritic anterior ischemic optic neuropathy (NAION)].

MATERIALS AND METHODS

Blood-flow velocities [peak systolic velocity (PSV), enddiastolic velocity (EDV)] of the ophthalmic artery (OA), central retinal artery (CRA), and nasal and temporal posterior ciliary arteries were measured using color Doppler imaging. Resistive index (RI) of all vessels was calculated (PSV-EDV/PSV). A total of 41 patients suffering from acute NAION (onset of symptoms <10 d) and 64 age-matched patients suffering from NTG were included in this prospective study.

RESULTS

No significant differences were recorded for either age or intraocular pressure inbetween the 2 groups. Systolic blood pressure was significantly higher in the NAION group, whereas no significant differences were recorded for the diastolic blood pressure. Only 3 color Doppler imaging parameters were found to differ significantly. The PSV (P<0.005) and EDV (P<0.02) in the CRA were significantly higher in NTG patients. Furthermore, the RI in the OA was significantly higher in the NAION patients (P<0.005).

CONCLUSIONS

Decreased blood-flow velocities in the CRA and a higher RI in the OA can be recorded in NAION patients as compared with NTG. No differences with regard to the posterior ciliary arteries' velocities were recorded. Ocular hemodynamics are suspected to play a critical role in NAION and NTG, whereas the blood-flow disturbances seem to be more severe in NAION than in NTG.

Quantitative analysis of choriocapillaris in non-human primates using swept-source optical coherence tomography angiography (SS-OCTA)

The choriocapillaris is a unique vascular plexus located posterior to the retinal pigment epithelium. In recent years, there is an increasing interest in the examination of the interrelationship between the choriocapillaris and eye diseases. We used several techniques to study choroidal perfusion, including laser Doppler flowmetry, laser speckle flowgraphy, and optical coherence tomography angiography (OCTA), but with the latter no standardized algorithm for quantitative analysis has been provided. We analyzed different algorithms to quantify flow voids in non-human primates that can be easily implemented into clinical research. In-vivo, high-resolution images of the non-human primate choriocapillaris were acquired with a swept-source OCTA (SS-OCTA) system with 100kHz A-scan/s rate, over regions of 3 × 3 mm² and 12 × 12 mm². The areas of non-perfusion, also called flow voids, were segmented with a structural, intensity adjusted, uneven illuminance-compensated algorithm and the new technique was compared to previously published methods. The new algorithm shows improved reproducibility and may have applications in a wide array of eye diseases including age-related macular degeneration (AMD).

Peripapillary microvasculature in the retinal nerve fiber layer in glaucoma by optical coherence tomography angiography: focal structural and functional correlations and diagnostic performance

Purpose

To quantify peripapillary microvasculature within the retinal nerve fiber layer (RNFL) in primary open-angle glaucoma (POAG) and normal eyes, determine association of perfusion parameters with structural and functional measures, and report diagnostic accuracy of perfusion parameters.

Patients and methods

POAG and normal patients underwent 6×6 mm² optic nerve head scans (Angioplex optical coherence tomography angiography [OCTA]; Cirrus HD-OCT 5000) and Humphrey Field Analyzer II-i 24-2 visual field (VF) testing. Prototype software performed semiautomatic segmentation to create RNFL en face images and quantified vessel area density (VAD), vessel skeleton density (VSD), and vessel complexity index (VCI) in the optic nerve head globally and focally. Generalized estimating equations models assessed association of OCTA parameters with VF mean deviation (MD) and RNFL thickness.

Results

Thirty-eight POAG and 17 normal eyes were studied. Global VAD, VSD, and VCI were reduced in mild POAG vs normal (P<0.02) and moderate-severe vs mild POAG (P<0.04). Stepwise focal reductions across disease stage were demonstrated for OCTA parameters in the inferior hemisphere (P<0.05); reduction in OCTA parameters in mild POAG vs normal was demonstrated in inferior and superior quadrants (P<0.05). Reduced global VF MD was associated with reduced VAD, VSD, and VCI (P=0.0007, 0.0013, <0.0001; R²=0.449, 0.312, 0.399, respectively), and global RNFL thickness was associated with VAD, VSD, and VCI (P<0.0001; R²=0.499, 0.524, 0.542), superior and inferior hemifield MD were associated with corresponding VAD, VSD, and VCI (P≤0.001; R² from 0.208 to 0.513). RNFL thickness in all quadrants was associated with corresponding OCTA parameters (P<0.05; R² from 0.213 to 0.394), except temporal VAD and VCI. Area under curves for VAD, VSD, and VCI demonstrated good diagnostic ability (0.868, 0.855, 0.868; P<0.0001).

Conclusion

Glaucomatous eyes showed stepwise reductions in RNFL microcirculation across severity; focal reductions in the inferior hemisphere and inferior and superior quadrants were most significant. OCTA parameters had stronger associations with structural rather than functional measures of glaucoma.

OPHTHALMIC ARTERY AND CENTRAL RETINAL ARTERY DOPPLER PATTERNS IN PRIMARY OPEN ANGLE GLAUCOMA PATIENTS AT THE LAGOS UNIVERSITY TEACHING HOSPITAL, NIGERIA

BACKGROUND

Circulatory abnormalities of retrobulbar vessels are increasingly being linked to the aetiopathogenesis of primary open angle glaucoma. These abnormalities can be assessed with a colour Doppler Imaging of retrobulbar vessels.

AIMS AND OBJECTIVES

To compare the Doppler ultrasound patterns of central retinal artery and ophthalmic artery in new patients with primary open angle glaucoma (POAG) diagnosis with those of non-glaucomatous group.

DESIGN OF THE STUDY

A hospital-based, comparative, cross-sectional study.

SETTING

Department of Ophthalmology (Guinness Eye Centre) and Department of Radiology, Lagos University Teaching Hospital, Idi-Araba, Lagos, Nigeria.

MATERIALS AND METHODS

End diastolic velocity (EDV), Peak systolic velocity (PSV) and resistivity index (RI) were measured in the central retinal artery (CRA) and ophthalmic artery (OA) of both eyes of newly diagnosed POAG patients. The CDI values of newly diagnosed POAG patients were compared with age-gender matched non-glaucomatous group. The Doppler values of the better and worse eye of patients with asymmetrical POAG were also compared.

RESULTS

One hundred subjects (200 eyes) comprising of 50 POAG patients and 50 non-glaucomatous healthy subjects were recruited for this study. The male to female ratio was 1:1.1(24 males and 26 females) for POAG patients and 1:1 (25 males and 25 females) for non-glaucomatous subjects. The CRA and OA in both eyes of POAG patients had a significantly lower mean EDV and PSV compared with those of non-glaucomatous group (p< 0.001). The CRA and OA in both eyes of POAG patients had a significantly higher mean RI compared with those of non-glaucomatous group (p< 0.001). A significant positive Pearson correlation was seen between the IOP and the RI in the CRA and OA in both eyes. Also, statistically significant negative Pearson correlations were seen between the IOP and the PSV and EDV in the OA and CRA in both eyes.

CONCLUSION

This study demonstrated a significant reduction in EDV and PSV as well as an increase in RI of the CRA and OA in both eyes among POAG patients compared to the non-glaucomatous group.

Randomized controlled trial of electro-stimulation therapies to modulate retinal blood flow and visual function in retinitis pigmentosa

PURPOSE

We examined changes in visual function and ocular and retinal blood flow (RBF) among retinitis pigmentosa (RP) participants in a randomized controlled trial of electro-stimulation therapies.

METHODS

Twenty-one RP participants were randomized (1:1:1) to transcorneal electrical stimulation (TES) at 6 weekly half-hour sessions, electro-acupuncture or inactive laser acupuncture (sham control) at 10 half-hour sessions over 2 weeks. Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity (VA), quick contrast sensitivity function, Goldmann visual fields, AdaptDx scotopic sensitivity, spectral flow and colour Doppler imaging of the central retinal artery (CRA), and RBF in macular capillaries were measured twice pre-treatment, after 2 TES sessions, within a week and a month after intervention completion.

RESULTS

We measured a significant improvement in retrobulbar CRA mean flow velocity for both the TES (p = 0.038) and electro-acupuncture groups (p = 0.001) on average after 2 weeks of treatment when compared to sham controls. Transcorneal electrical simulation (TES) and electro-acupuncture subjects had significant 55% and 34% greater increases, respectively, in RBF in the macular vessels when compared to sham controls (p < 0.001; p = 0.008) within a week of completing six TES sessions or a month after electro-acupuncture. There was a significant difference in the proportion of eyes that had improved visual function when comparing the three intervention groups (p = 0.038): four of seven TES subjects (57%), two of seven electro-acupuncture subjects (29%) and none of the seven control subjects (0%) had a significant visual improvement outside of typical test-retest variability at two consecutive post-treatment visits.

CONCLUSION

Increased blood flow following electro-stimulation therapies is an objective, physiological change that occurred in addition to visual function improvements in some RP patients.

Diurnal Variations of Peripapillary and Macular Vessel Density in Glaucomatous Eyes Using Optical Coherence Tomography Angiography

PURPOSE

The purpose of this study was to investigate the diurnal variation in peripapillary and macular vessel density (VD) measurements using optical coherence tomographic angiography (OCT-A) and its correlation to intraocular pressure (IOP) changes in glaucoma patients.

METHODS

Prospective, observational cross-sectional study including 37 patients (74 eyes; age, 63.8±12.9 y) with open-angle glaucoma. OCT-A imaging and IOP measurements were performed at 08:00, 11:00, 14:00, and 16:00 timepoints on a single day. At each timepoint, 2 scan protocols were used to generate 3-dimensional en face OCT angiograms: 4.5×4.5-mm scan centered on the optic nerve head and 6×6-mm scan centered on the fovea. For each scan mode, the "radial peripapillary capillary" segment, composed of the vasculature of the retinal nerve fiber layer and ganglion cell layer, was calculated. Two trained readers reviewed OCT-A image quality. Only scans with signal strength intensity (SSI) higher than 46 and without image artifacts interfering with measurements were included. Variation in VD measurements assessed using analysis of variance (ANOVA) and the association between VD and IOP changes assessed using linear mixed modeling methods.

RESULTS

The optic nerve head and peripapillary VD measurements at 14:00 and 16:00 timepoints were greater than the measurements at 08:00 and 11:00 timepoints. The 14:00 and 16:00 VD measurements were statistically significantly greater (P<0.05) than the 08:00 measurements for the whole en face (50.1% and 50.1% vs. 49.4%), inside disc (50.6% and 50.5% vs. 49.6%), and average peripapillary (58.2% and 58.5% vs. 57.5%) VDs. The macular VD measurements at the 14:00 timepoint were greater than the measurements at 08:00 and 11:00 timepoints. Changes in VD were significantly associated with changes in SSI but not IOP.

CONCLUSIONS

Diurnal changes in OCT-A-measured VD in glaucoma patients were small and clinically insignificant. These changes were not associated with IOP changes.

Assessment of choroidal blood flow using laser speckle flowgraphy

Background/aims

There is considerable interest in novel techniques to quantify choroidal blood flow (CBF) in humans. In the present study, we investigated a novel technique to measure CBF based on laser speckle flowgraphy (LSFG) in healthy subjects.

Methods

This study included 31 eyes of 31 healthy, non-smoking subjects aged between 19 and 74 years. A commercial LSFG instrument was used to measure choroidal vessel diameter (CVD) and relative flow volume (RFV) in choroidal vessels that were identified on fundus photos, an approach that was used previously only for retinal vessels. The reproducibility and the effect of isometric exercise on these parameters were investigated. The latter was compared with measurement of subfoveal CBF using laser Doppler flowmetry (LDF).

Results

Intraclass correlation coefficients for CVD and RFV were higher than 0.8 indicating excellent reproducibility. During isometric exercise, we observed an increase in ocular perfusion pressure of approximately 60% (P<0.001). The increase in RFV and CBF was lower, but also highly significant versus baseline (at minute 6 of isometric exercise: RFV 10.5%±4.2%, CBF 8.3%±3.6%; P<0.001 each) indicating choroidal autoregulation.

Conclusion

LSFG may be a novel approach to study blood flow in choroidal vessels. Data are reproducible and show good agreement with LDF data.

Trial registration number

NCT02102880, Results.

Reduced Central Retinal Artery Blood Flow Is Related to Impaired Central Visual Function in Retinitis Pigmentosa Patients

PURPOSE

We evaluated the test-retest repeatability of blood flow velocities in the retrobulbar central retinal artery (CRA) and explored whether reduced blood flow is related to the degree of visual function loss in retinitis pigmentosa (RP) patients with wide range of disease severity.

MATERIALS AND METHODS

We measured CRA peak systolic velocity (PSV) and end diastolic velocity (EDV) to calculate mean flow velocity (MFV) in 18 RP patients using color Doppler imaging with spectral flow Doppler (GE Logiq7 ultrasound) twice in each eye at each of two visits within a month. At each of these two visits, we measured ETDRS visual acuity (VA), quick Contrast Sensitivity Function (qCSF), Goldmann visual fields (GVF), 10-2 Humphrey visual fields (HVF), and dark-adaptation at 5° from fixation with the AdaptDx; multifocal electroretinography (mfERG) was obtained at a single visit.

RESULTS

Mean coefficients of variation for PSV, EDV and MFV were 16.1-19.2% for within-visit measurements and 20.1-22.4% for between-visit measures. Across patients, greater visual function loss assessed with VA (p = 0.04), extinguished versus measurable amplitude in ring 1 for mfERG (p = 0.001), and cone-only versus rod function with the AdaptDx (p = 0.002) were statistically significantly correlated with reduced MFV in the CRA when included a multilevel multivariate regression model along with the qCSF and HVF results, which all together accounted for 47% of the total variance in MFV. GVF log retinal areas (V4e and III4e; p = 0.30 and p = 0.95, respectively) and measurable far peripheral vision during GVF testing (p = 0.66) were not significantly related to MFV.

CONCLUSIONS

MFV in the CRA decreased with impaired central vision due to loss of both rod and cone function, had good test-retest repeatability, and may serve as a biomarker outcome to determine the potential physiological basis for improvements in RP clinical trials of therapies with indirect effects on blood flow to the retina.

Colour Doppler analysis of ophthalmic vessels in the diagnosis of carotic artery and retinal vein occlusion, diabetic retinopathy and glaucoma: systematic review of test accuracy studies

Background

Colour Doppler analysis of ophthalmic vessels has been proposed as a promising tool in the diagnosis of various eye diseases, but the available diagnostic evidence has not yet been assessed systematically. We performed a comprehensive systematic review of the literature on the diagnostic properties of Colour Doppler imaging (CDI) assessing ophthalmic vessels and provide an inventory of the available evidence.

Methods

Eligible papers were searched electronically in (Pre) Medline, Embase and Scopus, and via cross-checking of reference lists. The minimum requirement to be included was the availability of original data and the possibility to construct a two-by-two table. Study selection, critical appraisal using the QUADAS II instrument and extraction of salient study characteristics was made in duplicate. Sensitivity and specificity was computed for each study.

Results

We included 11 studies (15 two-by-two tables) of moderate methodological quality enrolling 820 participants (range 30 to 118). In 44.4% participants were female (range 37–59% in specific subgroups). CDI was assessed for internal carotid stenosis, diabetic retinopathy, glaucoma, and branch or central retinal vein occlusion diagnosis. There was insufficient data to pool the results for specific illnesses. For the assessments of ophthalmic arteries, mean sensitivity was 0.69 (range 0.27–0.96) with a corresponding mean specificity of 0.83 (range 0.70–0.96). Mean sensitivity of the central retinal artery assessments was 0.58 (range 0.31–0.84) and the corresponding mean specificity was 0.82 (range 0.63–0.94).

Conclusions

Robust assessments of the diagnostic value of colour Doppler analysis remain uncommon, limiting the possibilities to extrapolate its true potential for clinical practice.

PROSPERO 2014:CRD42014014027.

Juxtapapillary choroid is thinner in normal-tension glaucoma than in healthy eyes

PURPOSE

To measure the juxtapapillary choroidal thickness in eyes with normal-tension glaucoma (NTG) and to compare it with healthy eyes.

METHODS

Twelve radial B-scan images of the optic nerve head (ONH) were obtained from 96 patients with NTG and 48 healthy subjects matched by age using swept-source (SS) optical coherence tomography (OCT). The juxtapapillary choroidal thickness was defined as the average choroidal thickness within 500 μm from the border tissue of Elschnig. Choroidal thinning in patients with NTG was assessed by calculating the relative choroidal thickness, defined as the ratio of the measured juxtapapillary choroidal thickness in each meridian to the corresponding value in age-matched healthy controls. Retinal nerve fibre layer (RNFL) damage as reflected by circumpapillary RNFL thickness (measured using spectral-domain OCT) was also assessed.

RESULTS

The juxtapapillary choroid was significantly thinner in NTG eyes than in healthy control eyes in the inferotemporal and superotemporal sectors. The relative choroidal thinning was topographically associated with the hemispheric location of dominant RNFL damage. The average juxtapapillary choroidal thickness was not associated with either the global RNFL thickness or the visual field mean deviation. Age and untreated intraocular pressure were significantly associated with the juxtapapillary choroidal thickness in NTG eyes in both univariate and multivariate analyses (all p < 0.05).

CONCLUSIONS

Decreased microvascular circulation in the ONH as a result of juxtapapillary choroidal thinning could be an important part of the pathogenesis of optic nerve damage in NTG.

Ocular blood flow in glaucoma - the Leuven Eye Study

PURPOSE

Elevated intra-ocular pressure (IOP) has been identified as a major risk factor for glaucoma. Additionally, extensive literature depicts a vascular dysfunction to exist in these patients. However, a large ocular blood flow-oriented trial to integrate these findings in the clinical setting is lacking. This study would likely help to identify which of these vascular data can be used as a clinical tool for screening and disease stratification.

METHOD

Prospective, cross-sectional, case-control hospital-based study. Patients with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), ocular hypertension (OHT), glaucoma suspects and healthy volunteers were recruited. In addition to a comprehensive ophthalmological examination, a vascular-oriented questionnaire was completed and ocular blood flow assessment (colour Doppler imaging of retrobulbar vessels, retinal oximetry, dynamic contour tonometry, optical coherent tomography enhanced-depth imaging of the choroid) were performed. Statistical analysis was based on multiple imputation to account for missingness.

RESULTS

A total of 614 subjects (291 males) were recruited between March and December 2013 (POAG: 214, NTG: 192; OHT: 27; glaucoma suspect: 41; healthy controls: 140). Glaucoma groups (NTG and POAG) were age and gender matched with the control group (p > 0.05). Glaucoma groups were paired in terms of functional and structural parameters (p > 0.08). Mean ocular perfusion pressure was higher in the glaucoma groups than in controls (p < 0.001). Glaucoma groups had lower retrobulbar velocities, higher retinal venous saturation and choroidal thickness asymmetries when compared to the healthy group, in line with the current literature.

CONCLUSIONS

The Leuven Eye Study stands as one of the largest clinical trials on ocular blood flow in glaucoma. The creation of this vast database may help integrate the vascular aspects of glaucoma into the clinical practice of glaucoma.

Optical coherence tomography angiography of stimulus evoked hemodynamic responses in individual retinal layers

Blood flow changes are highly related to neural activities in the retina. It has been reported that neural activity increases when flickering light stimulation of the retina is used. It is known that blood flow changes with flickering light stimulation can be altered in patients with vascular disease and that measurement of flicker-induced vasodilatation is an easily applied tool for monitoring functional microvascular alterations. However, details of distortions in retinal neurovascular coupling associated with major eye diseases are not well understood due to the limitation of existing techniques. In this study, flickering light stimulation was applied to mouse retinas to investigate stimulus evoked hemodynamic responses in individual retinal layers. A spectral domain optical coherence tomography (OCT) angiography imaging system was developed to provide dynamic mapping of hemodynamic responses in the ganglion cell layer, inner plexiform layer, outer plexiform layer and choroid layer before, during and after flickering light stimulation. Experimental results showed hemodynamic responses with different magnitudes and time courses in individual retinal layers. We anticipate that the dynamic OCT angiography of stimulus evoked hemodynamic responses can greatly foster the study of neurovascular coupling mechanisms in the retina, promising new biomarkers for retinal disease detection and diagnosis.

Value of Structural and Hemodynamic Parameters for the Early Detection of Primary Open-Angle Glaucoma

PURPOSE

To compare the diagnostic value of ocular blood flow parameters and choroidal thickness (CT) with standard structural parameters for early glaucoma detection.

METHODS

A total of 32 patients with pre-perimetric glaucoma were compared with 30 age-matched normal subjects. The thickness of the ganglion cell complex (GCC), retinal nerve fiber layer (RNFL), and the choroid and foveal loss volume (FLV) were measured by means of optical coherence tomography (OCT). Retrobulbar blood velocities (Color Doppler Imaging), corneal compensated intraocular pressure (IOPcc), and corneal hysteresis (CH) were also evaluated. Mean ocular perfusion pressure (MOPP) was calculated by measuring IOP and mean arterial blood pressure as MOPP = ([2/3 diastolic BP + 1/3 systolic BP] × 2/3-IOP). The value of each diagnostic indicator (z-value) was calculated using the Wilcoxon-Mann-Whitney test and the area under the receiver operating characteristic curve (AUC).

RESULTS

The following indicators had the largest AUC and diagnostic value (z-value): mean blood flow velocity in the vortex veins (AUC 1.0; z-value 5.35) and central retinal vein (0.85; 3.74), diastolic blood flow velocity in the central retinal artery (0.73; 2.74) and lateral short posterior ciliary arteries (0.71; 2.53), IOPcc (0.74; -2.9), CH (0.69; 2.24), CT (0.69; -2.28), GCC (0.67; 2.05), and FLV (0.66; -1.86) to discriminate pre-perimetric glaucoma from healthy subjects.

CONCLUSIONS

Interestingly, ocular hemodynamic parameters performed better than structural parameters in detecting early glaucoma. This highlights the potential of techniques to measure ocular blood flow in glaucoma diagnostics independently of the question whether perfusion abnormalities are a cause or a consequence of the disease.