Amplitude Decorrelation Research Articles

Contribution of systemic factors on macular vessel density: a sex-specific population-based study.

To evaluate the influence of systemic factors on macular vessel density in quantitative Optical Coherence Tomography Angiography (OCTA) by sex. A cross-sectional study. A total of 2018 adults were recruited in this study. Participants were excluded (n=964) due to missing data, eye-related problems, or low OCTA scan quality. Macular vessel densities were measured with OCTA using split-spectrum amplitude decorrelation angiography algorithm. Only the data from the right eyes were selected for analysis. Multivariable linear regression analysis was performed to determine the associations between macular vessel density and obesity-related systemic factors in each gender group. The right eyes of 1054 participants (59.6% women) were enrolled. Men had significantly higher obesity parameters and associated risk factors. In multivariable linear regression analysis in men, older age and type 2 diabetes mellitus were independently associated with lower superficial retinal vessel density (β = -0.37, p = 0.002; β = -1.22, p = 0.03) and deep retinal vessel density, respectively (β = -0.66, p < 0.001; β = -1.76, p = 0.02); positive association was also observed between body mass index (BMI) and superficial retinal vessel density (β = 0.56, p = 0.02). In women, only higher systolic blood pressure was independently associated with a lower deep retinal vessel density (β = -0.50, p = 0.003). This large cross-sectional study shows that older age and type 2 diabetes mellitus are associated with lower superficial and deep retinal capillary vessel density in men. This may help clinicians better understand how systemic factors influence retinal vessel density in different genders and future studies can ascertain more potential sex differences.

Light conditions influence optic nerve OCT angiography parameter in healthy subjects with neutral pupils

Optical coherence tomography angiography measurements are influenced by a range of environmental factors as blood pressure and physical fitness. The present study aimed to evaluate the effects of light and dark exposure in eyes with neutral and mydriatic pupils on vessel density in the macular and optic nerve head regions, as measured using optical coherence tomography angiography (OCTA). 55 eyes of 55 healthy volunteers (28 patients with neutral pupils; 27.18 ± 4.33 years) were examined using a high-speed and high-resolution spectral-domain OCT XR Avanti system with a split-spectrum amplitude de-correlation angiography algorithm. OCTA imaging was performed after dark adaptation and after exposure to light. The vessel density data of the superficial and deep retinal macular and optic nerve head region OCT-angiogram were analyzed for these two light conditions. Through Bonferroni correction for multiple testing, the p- value was adapted from 0.05 to 0.017. In eyes with neutral pupils, a significant increase was found in the capillary region of the optic nerve head region (p = 0.002), comparing dark- and light-adaptation. In the macular region of eyes with neutral (p = 0.718) and mydriatic pupils (p = 0.043), no significant differences were observed, as were any in the optic nerve head region of the mydriatic eyes (p = 0.797). This observation suggests that light conditions could be a possible factor influencing OCTA measurements. After dark exposure, vessel density data were significantly different between eyes with neutral and mydriatic pupils (nerve head region: p < 0.0001, superficial macula: p < 0.0001, deep macula: p = 0.0025). These data warn for the effect of mydriatic drops on vessel density measurements.

In vivo imaging of renal microvasculature in a murine ischemia–reperfusion injury model using optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) provides three-dimensional structural and semiquantitative imaging of microvasculature in vivo. We developed an OCTA imaging protocol for a murine kidney ischemia–reperfusion injury (IRI) model to investigate the correlation between renal microvascular changes and ischemic damage. Mice were divided into mild and moderate IRI groups according to the duration of ischemia (10 and 35 mins, respectively). Each animal was imaged at baseline; during ischemia; and at 1, 15, 30, 45, and 60 mins after ischemia. Amplitude decorrelation OCTA images were constructed with 1.5-, 3.0-, and 5.8-ms interscan times, to calculate the semiquantitative flow index in the superficial (50–70 μm) and the deep (220–340 μm) capillaries of the renal cortex. The mild IRI group showed no significant flow index change in both the superfial and the deep layers. The moderate IRI group showed a significantly decreased flow index from 15 and 45 mins in the superficial and deep layers, respectively. Seven weeks after IRI induction, the moderate IRI group showed lower kidney function and higher collagen deposition than the mild IRI group. OCTA imaging of the murine IRI model revealed changes in superficial blood flow after ischemic injury. A more pronounced decrease in superficial blood flow than in deep blood flow was associated with sustained dysfunction after IRI. Further investigation on post-IRI renal microvascular response using OCTA may improve our understanding of the relationship between the degree of ischemic insult and kidney function.

Amplitude-decorrelation avoiding spectral artifacts of sound field synthesis in the anechoic chamber or free sound field

Sounds to appear in directions between the loudspeakers will typically activate neighboring loudspeakers with the same signal when spatially rendered. The resulting interference causes frequency- and position-dependent cancellation in the superimposed sound field. While keeping the number of active loudspeakers uniformly small is often enough to have the few acoustic reflections of a studio environment conceal the unwanted cancellations, they will remain a problem when synthesizing sound fields in the anechoic chamber or free field. Our contribution investigates short filters for amplitude decorrelation to reduce this problem. The filters supply neighboring loudspeakers via frequency responses that are mutually exclusive and hereby avoid cancellation in the superimposed soundfield. This only works at the expense of requiring a minimum spread to ensure a spectrally balanced synthesis, i.e., by avoiding to activate single filtered loudspeaker, alone. We present a listening experiment investigating in how far the proposed filter strategy is able to improve the spectral stability within a reasonable range of motion for a seated listener, in the anechoic chamber. Other thinkable approaches are investigated for comparison.

Performance comparison of amplitude-decorrelation and speckle variance algorithms in spectrometer-based OCT angiography

In this work, optical coherence tomography angiography (OCTA) was implemented on a spectrometer-based spectral domain OCT (SD-OCT) that was built on Michelson interferometer. Three methods of speckle analysis were implemented, i.e. amplitude decorrelation (AD), speckle variance (SV), and speckle to mean variance (SMV). The SMV is an in-house developed algorithm to accommodate the poor signal-to-noise ratio performance of the spectrometer-based SD-OCT. To compare the performance of the implemented algorithms, a flow phantom was constructed by embedding a capillary tube inside a diluted milk gel that represented static tissue. To mimic a blood flow beneath skin, diluted milk was pumped through the capillary tube with speeds of 0.3 to 3.5 mm·s−1 by using a syringe pump system. The performance of each OCTA algorithm, in terms of contrast-to-noise ratio (CNR), were measured and compared. The result shows that SMV algorithm provided the highest relative CNR value of 1.34, which is a 111 % improvement over the performance of SV algorithm.

Endoscopic optical coherence tomography angiography using inverse SNR-amplitude decorrelation features and electrothermal micro-electro-mechanical system raster scan.

Angiogenesis is closely associated with tumor development and progression. Endoscopic optical coherence tomography angiography (OCTA) enables rapid inspection of mucosal 3D vasculature of inner organs in the early-stage tumor diagnosis; however, it is limited by instabilities of the optical signal and beam scanning. In the phase-unstable swept source OCTA (SS-OCTA), amplitude decorrelation was used to compute the motion-induced changes as motion contrast. The influence of the random noise-induced amplitude fluctuations on decorrelation was characterized as a function of inverse signal-to-noise ratio (SNR) with a multi-variate time series (MVTS) model and statistical analysis. Then, the noise-induced decorrelation artifacts in static tissue regions were eliminated by applying a flow mask based on the statistical relation between inverse SNR (iSNR) and amplitude decorrelation (IDa), which was named IDa-OCTA. In addition, a distal stepwise raster scan was realized with a low-voltage electrothermal micro-electro-mechanical system (ET-MEMS)-based catheter for endoscopic imaging, whereby the stable and repeatable B-scans at each step suppressed the decorrelation noise induced by the spatial mismatch between paired scans. The derived IDa relation was validated through numerical simulation and flow phantom experiments. In vivo human buccal mucosa imaging was performed to demonstrate the endoscopic IDa-OCTA imaging. In this, the subsurface structure and vasculature were visualized in a rapid and depth-resolved manner. The rapid 3D vasculature visualization realized by the endoscopic IDa-OCTA improves the diagnosis of early tumors in internal organs.

Endoscopic OCT Angiography Using Clinical Proximal-End Scanning Catheters

Endoscopic optical coherence tomography angiography (OCTA) is a promising modality to inspect the microvasculature of inner organs in the early-stage tumor diagnosis. However, an endoscopic clinical proximal-end scanning catheter has limited flow imaging capability due to the nonuniform rotational distortion (NURD) and physiological motion. In this study, a combined local and global (CLG) optical flow algorithm was used to estimate the motion vectors caused by NURD and physiological motion. The motion vectors were used to bicubic-interpolation-resample the OCT structure to ensure that the circumferential pixels were equally spaced in the space domain. Then, angiograms were computed based on the statistical relation between inverse SNR (iSNR) and amplitude decorrelation (IDa), termed as IDa-OCTA. Finally, the ability of this technique for endoscopic OCTA imaging was demonstrated by flow phantom experiments and human nailfold capillary imaging.

Analysis of choroidal vessel density in patients with multiple sclerosis

Multiple Sclerosis (MS) is a chronic neuro inflammatory disease which leads to progressive disability. Recent evidence suggests that vascular impairment may contribute to MS onset and progression. Optical Coherence Tomography Angiography (OCT-A) has emerged as an important imaging tool which should allow further exploration of the vessel changes in the pathogenesis and prognosis of MS. To quantify the vascular density (VD) of the choroid (CH) and choriocapillaris (CC) in patients with MS, comparing with normal eyes. 45 eyes of 45 MS patients [31 female; mean age (years ± SD) 41,87 ± 11.04; axial length (AL) (AL ± SD) 23.68 ± 0.90) and 45 aged-matched control subjects (33 female; mean age 39,.6 ± 8,93; AL 23.36 ± 0.75] were enrolled in this prospective study. We obtained OCT-A images based on a full-spectrum amplitude de-correlation angiography (FSADA) algorithm. The OCT-A images of the CH and CC were used for quantitative assessment in three regions of the fovea, namely, Region 1 (0–500 μm) Region 2 (500–1000 μm) and Region 3 (1000−1500 μm). Relationships of VD between MS patients with and without optic neuritis (ON) and controls were investigated by binary vessel maps generated from OCT-A slabs and analyzed using ImageJ software. Compared to controls, in eyes with MS, CH VD was significantly decreased in Region 2 (p = 0.01) and Region 3 (p < 0.01). CCVD was not different between the groups although showing a decreasing tendency in the MS group. Between eyes with and without ON there were a tendency to reduced VD in the ON group in all regions analyzed for both CH and CC layer. All the layers analyzed revealed a positive correlation between CH VD and CC VD and a negative correlation between CC VD and AL. Although studies have assessed retinal VD in MS using OCT-A, the choroidal vasculature in MS remains understudied. Our results cautiously suggest a functional circulatory disturbance of choroidal vasculatures in MS patients, mainly in those who have previous ON history.

Signal properties of split-spectrum amplitude decorrelation angiography for quantitative optical coherence tomography-based velocimetry.

Split-spectrum amplitude-decorrelation angiography (SSADA) is a noninvasive and three-dimensional angiographic technique with a microscale spatial resolution based on optical coherence tomography. The SSADA signal is known to be correlated with the blood flow velocity and the quantitative velocimetry with SSADA has been expected; however, the signal properties of SSADA are not completely understood due to lack of comprehensive investigations of parameters related to SSADA signals. In this study, phantom experiments were performed to comprehensively investigate the relation of SSADA signals with flow velocities, time separations, particle concentrations, signal-to-noise ratios, beam spot sizes, and viscosities, and revealed that SSADA signals reflect the spatial commonality within a coherence volume between adjacent A-scans.

Deep learning differentiates between healthy and diabetic mouse ears from optical coherence tomography angiography images.

We trained a deep learning algorithm to use skin optical coherence tomography (OCT) angiograms to differentiate between healthy and type 2 diabetic mice. OCT angiograms were acquired with a custom‐built OCT system based on an akinetic swept laser at 1322 nm with a lateral resolution of ∼13 μm and using split‐spectrum amplitude decorrelation. Our data set consisted of 24 stitched angiograms of the full ear, with a size of approximately 8.2 × 8.2 mm, evenly distributed between healthy and diabetic mice. The deep learning classification algorithm uses the ResNet v2 convolutional neural network architecture and was trained on small patches extracted from the full ear angiograms. For individual patches, we obtained a cross‐validated accuracy of 0.925 and an area under the receiver operating characteristic curve (ROC AUC) of 0.974. Averaging over multiple patches extracted from each ear resulted in the correct classification of all 24 ears.

Peripapillary perfused capillary density in true versus pseudoexfoliation syndrome: An OCTA study.

PurposeTo compare peripapillary perfused capillary density (PCD) among eyes with true exfoliation syndrome (TEX), eyes with pseudoexfoliation syndrome (PEX), and healthy control eyes.Materials and methodsIn this observational cross-sectional study, eyes with and without TEX or PEX were assessed by optical coherence tomography angiography (OCTA) imaging. Bilateral OCTA images (4.5 × 4.5 mm2) centered at the optic nerve head were obtained using a commercial spectral domain OCTA system. Optic nerve head perfusion was quantified using the split-spectrum amplitude decorrelation angiography algorithm. Categorical and continuous variables were compared using the chi-squared test and one-way analysis of variance, respectively. The generalized estimating equation was used to adjust for confounding factors and determine inter-ocular associations.ResultsWe enrolled 39 eyes with TEX, 31 eyes with PEX, and 32 control eyes. There were no significant differences among the three groups regarding age, intraocular pressure, cup-to-disc ratio, blood pressure, or axial length (all p>0.05). There were significant differences in global PCD among the three groups (p = 0.01). There were significant differences in annular PCD between the TEX and PEX groups (p = 0.027).ConclusionsWhile both global and annular PCDs did not differ between the TEX and control groups, greater loss of annular PCD in the PEX group than in the TEX and control groups suggests more pronounced microvascular disturbance in PEX.Synopsis/PrecisGreater microvascular attenuation in PEX compared with TEX and normal control measured by OCTA.

Cooperative Low-Rank Models for Removing Stripe Noise From OCTA Images.

Optical coherence tomography angiography (OCTA) is an emerging non-invasive imaging technique for imaging the microvasculature of the eye based on phase variance or amplitude decorrelation derived from repeated OCT images of the same tissue area. Stripe noise occurs during the OCTA acquisition process due to the involuntary movement of the eye. To remove the stripe noise (or 'destriping') effectively, we propose two novel image decomposition models to simultaneously destripe all the OCTA images of the same eye cooperatively: cooperative uniformity destriping (CUD) model and cooperative similarity destriping (CSD) model. Both the models consider stripe noise by low-rank constraint but in different ways: the CUD model assumes that stripe noise is identical across all the layers while the CSD model assumes that the stripe noise at different layers are different and have to be considered in the model. Compared to the CUD model, CSD is a more general solution for real OCTA images. An efficient solution (CSD+) is developed for model CSD to reduce the computational complexity. The models were extensively evaluated against state-of-the-art methods on both synthesized and real OCTA datasets. The experiments demonstrated not only the effectiveness of the CSD and CSD+ models in terms of peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) and CSD+ is twice faster than CSD, but also their beneficiary effect on the vessel segmentation of OCTA images. We expect our models will become a powerful tool for clinical applications.

Macular Vessel Density Measured With Optical Coherence Tomography Angiography and Its Associations in a Large Population-Based Study

We investigate macular perfusion and the systemic and ocular associations in a population-based setting. In this cross-sectional study, 2018 adults residing in Hong Kong underwent detailed ophthalmic examinations after consenting to participate. Macular perfusion was measured with optical coherence tomography angiography (OCTA) using the split-spectrum amplitude decorrelation angiography algorithm. The parafoveal flow index and vessel area density were quantified using automated custom-built software. Of the 2018 participants, the OCTA measurements were available for 1940, and 1631 (84.1%) had good quality scans. The right eyes of these 1631 participants (43.1% men) were included for final analysis. Mean age was 49.8 years (range, 18-92 years). Mean global macular vessel density was 47.3% and 55.1% for the superficial and deep retinal layers, respectively. In multivariate analysis, lower superficial vessel density remained significantly associated with lower signal strength index (SSI; P < 0.001, standardized β = 0.607) and male sex (P < 0.001, β = 0.162), and borderline associated with older age (P = 0.09, β = -0.045) and longer axial length (AL; P = 0.09, β = -0.037), while lower deep layer vessel density was significantly associated with lower SSI (P < 0.001, standardized β = 0.667), longer AL (P < 0.001, β = -0.097), and higher creatinine (P < 0.001, β = -0.072). This large population-based study provided normative OCTA data of macular vessel density and demonstrated that a lower superficial retinal vessel density was significantly associated with lower SSI and male sex, while a lower deep layer retinal vessel density was significantly associated with lower SSI, longer AL, and higher level of creatinine. These associations must be considered when interpreting clinical quantitative OCTA data.

Vessel density and En-face segmentation of optical coherence tomography angiography to analyse corneal vascularisation in an animal model

BackgroundOptical coherence tomography angiography (OCTA) is a novel non-invasive angiography technology that has recently been extensively studied for its utility in anterior segment imaging. In this study, we compared a split-spectrum amplitude decorrelation angiography (SSADA) OCTA and an optical micro-angiography (OMAG SD) OCTA system to current angiographic technique, indocyanine green angiography (ICGA), to assess corneal vascularisation in an animal model.MethodsWe imaged 16 rabbits, (one eye per animal) with corneal vascularisation using SSADA OCTA (AngioVue; Optovue Inc., USA), OMAG OCTA (Angioscan; RS-3000 Nidek Co. Ltd., Japan) and ICGA in the same region of interest of the cornea at successive time-points. We then analysed all scanned images for vessel density measurements and used paired t-tests and Bland-Altman plots to examine for significant differences. The en-face segmentation images from each of the OCTA scans were also extracted and were matched at every 50 μm segmentation to be compared for vessel density at the respective depths.ResultsBland-Altman plots revealed a good agreement between all three imaging techniques (P > 0.05) for all vessel density measurements computed, and the ranges of 95% limit of agreement were acceptable from a clinical perspective. No significant difference was reported, with ICGA (μ = 16.52 ± 8.94%) being more comparable to the OMAG OCTA (μ = 16.23 ± 9.51%; p = 0.50) than the SSADA OCTA (μ = 17.09 ± 7.34%; p = 0.33) system. Also, a good correlation value (r > 0.9) was obtained when comparing the vessel density measurements of the en-face segmentations between the OCTA systems.ConclusionsComparable vessel density quantification between the two OCTA systems, and with ICGA was obtained. Segmentation analysis of the vasculature at different depths showed varied performance in the two OCTA systems relative to each other. The implications of the study may help to aid in the development of better OCTA algorithms for the anterior segment and its use in clinical translational research.

Optical Coherence Tomography Angiography in Glaucoma.

Optical coherence tomography angiography (OCTA) comprises different OCT-based technologies developed for non-invasive assessment and measurement of optic nerve head and retinal perfusion. Currently the most clinically established approach is based on the split spectrum amplitude decorrelation algorithm, which detects moving red blood cells and eliminates all other information. The two main clinical fields in which OCTA offers clinically useful information are investigation of the macular retina (e.g. in macular degeneration and diabetic macular disease) and glaucoma. For glaucoma, the optic nerve head and the peripapillary retinal perfusion in the retinal nerve fiber layer, and the superficial perifoveal macular vasculature are the areas of interest. This review provides a comprehensive summary of the most important current and potential future applications of OCTA in glaucoma, but it does not address the nonglaucomatous optic nerve head or peripapillary and macular diseases.

Choriocapillaris and retinal vascular plexus density of diabetic eyes using split-spectrum amplitude decorrelation spectral-domain optical coherence tomography angiography.

Split-spectrum amplitude decorrelation angiography for spectral-domain optical coherence tomography has enabled detailed, non-invasive assessment of vascular flow. This study evaluates choriocapillaris and retinal capillary perfusion density (CPD) in diabetic eyes using optical coherence tomography angiography (OCTA). Records of 136 eyes that underwent OCTA imaging at a single institution were reviewed. Eyes were grouped as non-diabetic controls (37 eyes), patients with diabetes mellitus (DM) without diabetic retinopathy (DM without DR, 31 eyes), non-proliferative diabetic retinopathy (NPDR, 41 eyes) and proliferative diabetic retinopathy (PDR, 27 eyes). Quantitative CPD analyses were performed on OCTA images for assessing perfusion density of the choriocapillaris and retinal plexus for all patients and compared between groups. Eyes with NPDR and PDR showed significantly decreased choriocapillaris CPD compared with controls, while DM eyes without DR did not show significant change. Choriocapillaris whole-image CPD was decreased by 8.3% in eyes with NPDR (p<0.01) and decreased by 7.1% in eyes with PDR (p<0.01). Choriocapillaris parafoveal CPD was decreased by 8.9% in eyes with NPDR (p<0.01) and decreased by 8.2% in eyes with PDR (p<0.01). Compared with controls, only eyes with PDR showed significantly decreased retinal CPD, as well as significantly increased foveal avascular zone (FAZ) area. In those patients, retinal whole-image CPD was decreased by 9.7% (p<0.01), retinal foveal CPD was decreased by 20.5% (p<0.01) and retinal parafoveal CPD was decreased by 11.4% (p<0.01). FAZ area was increased by 50.9% (p<0.01). Choriocapillaris and retinal CPD are reduced in diabetic retinopathy, while FAZ area is increased in eyes with PDR. Vascular changes captured by new imaging modalities can further characterise diabetic choroidopathy.

Reliability of Vessel Density Measurements in the Peripapillary Retina and Correlation with Retinal Nerve Fiber Layer Thickness in Healthy Subjects Using Optical Coherence Tomography Angiography

Purpose: To evaluate the reliability of vessel density measurements in the peripapillary retina using optical coherence tomography angiography (OCT-A) and to analyze the correlation with retinal nerve fiber layer (RNFL) thickness in healthy subjects. Method: Thirty-five healthy volunteers were recruited in the study. The optic disc region was scanned three times with spectral-domain OCT (SD-OCT) and split-spectrum amplitude decorrelation angiography by two skilled examiners. Vessel density of the peripapillary retina was automatically calculated by the software RTVue-XR (version 2015.1.1.98). The RNFL thickness on the optic nerve head was measured by SD-OCT. The coefficient of variation (CV), coefficient of repeatability, and intraclass correlation coefficients (ICC) were calculated for intraobserver repeatability. The Bland-Altman analysis was used to determine interobserver reproducibility. Correlations between peripapillary retinal vessel density and RNFL thickness were analyzed using a multivariable linear regression. Results: The mean age of the volunteers was 47.0 ± 29.7 years. The intraobserver repeatability in different sectors of the peripapillary retina was good with a high coefficient of repeatability, low CV (< 0.2%), and high ICC (0.847–0.952). The interobserver reproducibility was also good in different sectors, but should be interpreted with caution due to the difference bias caused by different observers in some quadrants. There was a significant positive correlation between vessel density and RNFL thickness; optic disc rim area and disc area were negatively related to vessel density (p = 0.008 and p = 0.001, respectively). Conclusion: Vessel density measurements showed good repeatability and reproducibility by OCT-A in the peripapillary retina, the vessel density was positively related to RNFL thickness and negatively related to optic disc area and rim area.

Reduced Retinal Vessel Density in Primary Angle Closure Glaucoma: A Quantitative Study Using Optical Coherence Tomography Angiography.

The purpose of this article is to investigate the changes in the retinal vasculature in different parts of the fundus in eyes with primary angle closure glaucoma (PACG). Healthy subjects and those with PACG were enrolled. Optical coherence tomography and a split-spectrum amplitude decorrelation angiography algorithm were used to quantify the retinal vessel densities in the parafoveal and peripapillary areas. Thirty-nine eyes from 24 PACG patients and 39 eyes from 20 age-matched and sex-matched healthy subjects were included. The retinal vessel densities in the parafoveal and peripapillary areas and every sector of the 2 areas were significantly lower in the PACG eyes than in the healthy eyes. The difference was greater in the peripapillary area (11.75%) than in the parafoveal area (7.55%, P<0.05). In the PACG eyes, the vessel density in the peripapillary area correlated closely with the intraocular pressure, but that in the parafoveal area did not. When the PACG eyes were divided into groups with well-controlled and not well-controlled intraocular pressure (≤21 mm Hg or not), the vessel density and retinal nerve fiber layer thickness in the peripapillary area were much lower in the not well-controlled eyes (P<0.05), whereas the vessel density in the parafovea and the ganglion cell complex thickness were similar in the 2 subgroups. Retinal vessel density was significantly reduced in PACG eyes. The magnitude of this difference varied between the fundus areas, and was greater in the peripapillary area.

Changes in peripapillary blood vessel density in Graves’ orbitopathy after orbital decompression surgery as measured by optical coherence tomography angiography

ABSTRACTThe purpose is to evaluate the utility of optical coherence tomography (OCT) angiography in the evaluation of Graves’ orbitopathy (GO) and response to orbital decompression in patients with and without dysthyroid optic neuropathy (DON). This was a single-center, prospective case series in a cohort of 12 patients (24 orbits) with GO and ±DON, (6 orbits) who underwent bilateral orbital decompression. All patients underwent pre- and postoperative OCT angiography of the peripapillary area. Vessel density indices were calculated in a 4.5 mm × 4.5 mm ellipsoid centered on the optic disk using split-spectrum amplitude decorrelation angiography algorithm, producing the vessel density measurements. Mean change in vessel density indices was compared between pre- and postoperative sessions and between patients with and without DON. Patient 1, a 34-year-old male with GO and unilateral DON OD, showed a significant reduction in blood vessel density indices oculus dexter (OD) (DON eye) after decompression while a more modest reduction was found oculus sinister (OS) with the greatest change noted intrapapillary. Patient 2, a 50-year-old male with DON OU, showed worsening neuropathy following decompression OD that was confirmed by angiographic density indices. Patient 3, a 55-year-female with DON, showed a reduction in blood vessel density OD and increased density OS. Patients without DON showed overall less impressive changes in indices as compared to those with DON. Using OCT angiography, response to surgical treatment in GO orbits, more so in orbits with DON, can be demonstrated and quantified using vessel density indices with reproducibility.

Plexus-Specific Detection of Retinal Vascular Pathologic Conditions with Projection-Resolved OCT Angiography

To evaluate the projection-resolved (PR) optical coherence tomography angiography (OCTA) algorithm in detecting plexus-specific vascular abnormalities in retinal pathologies. Cross-sectional observational clinical study. Patients diagnosed with retinal vascular diseases and healthy volunteers. Eyes were imaged using an OCT system operating at 840 nm and employing the split-spectrum amplitude decorrelation algorithm. A novel algorithm suppressed projection artifacts inherent to OCTA. The volumetric scans were segmented and visualized on different plexuses. Qualitative observation of vascular abnormalities on both cross-sectional and en face PR-OCTA images. Eight illustrative cases are reported. In cases of diabetic retinopathy, retinal vessel occlusion, and retinitis pigmentosa, PR-OCTA detected retinal nonperfusion regions within deeper retinal plexuses not visualized by conventional OCTA. In age-related macular degeneration, cross-sectional PR-OCTA permitted the classification of choroidal neovascularization, and, in a case of retinal angiomatous proliferation, identified a vertical vessel contiguous with the deep capillary plexus. In macular telangiectasia, PR-OCTA detected a diving perifoveal vein and delineated subretinal neovascularization. Application of PR-OCTA promises to improve sensitive, accurate evaluation of individual vascular plexuses in multiple retinal diseases.