CHOROIDAL NEOVASCULAR AREA AND VESSEL DENSITY COMPARISON BETWEEN TWO SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY DEVICES

Combination of serum markers with optical coherence tomography angiography for evaluating neuromyelitis optica spectrum disorders and multiple sclerosis

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS), autoimmune inflammatory diseases of the central nervous system, affect the optic nerve and brain. A lumbar puncture to obtain biomarkers is highly invasive. Serum biomarkers and optical coherence tomography angiography (OCTA) are more accessible and less expensive than magnetic resonance imaging and provide reliable, reproducible measures of neuroaxonal damage. This study investigated the association between serum neurofilament light chain (sNfL), serum glial fibrillary acidic protein (sGFAP), and OCTA metrics. Serum sNfL and sGFAP levels, OCTA values, and clinical characteristics were compared among 91 patients with NMOSD, 81 patients with MS, and 34 healthy controls (HCs) at baseline and 1-year follow-up.

RESULTS

sNfL and sGFAP levels were higher while the sGFAP/sNfL quotients were significantly lower in NMOSD and MS patients than those in HCs. At baseline, the average thicknesses of the peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell-inner plexiform layer (mGC-IPL) were significantly smaller in NMOSD and MS patients than those in HCs (pRNFL: MS 92.0 [80.2; 101] μm, NMOSD 80.0 [59.0; 95.8] μm, vs HC 99.0 [92.0; 104] μm, p < 0.001; mGC-IPL: MS 74.5 [64.2; 81.0] μm, NMOSD 68.0 [56.0; 81.0] μm, vs HC 83.5 [78.0; 88.0] μm, p < 0.001). The vessel density (VD) and perfusion density (PD) were increased in MS patients without optic neuritis compared to HCs (VD: MS 16.7 [15.6; 17.9] HC 15.3 [13.4; 16.9], p = 0.008; PD: MS 0.41 [0.38; 0.43], HC 0.37 [0.32; 0.41], p = 0.017). In NMOSD patients without optic neuritis, sNfL was significantly associated with PD at baseline (r = 0.329, q = 0.041). The baseline and follow-up values of the sNfL level and average pRNFL and mGC-IPL thicknesses in MS patients showed significant differences. NMOSD patients showed significant differences between baseline and follow-up sNfL and sGFAP levels but not OCTA metrics.

CONCLUSION

Changes in retinal microvasculature might occur earlier than those in retinal structure and may therefore serve as a promising diagnostic marker for early NMOSD. The combination of serum markers and OCTA metrics could be used to evaluate and differentiate between MS and NMOSD.

Application of ImageJ in Optical Coherence Tomography Angiography (OCT-A): A Literature Review

Background

This study aimed to review the literature on the application of ImageJ in optical coherence tomography angiography (OCT-A) images.

Methods

A general search was performed in PubMed, Google Scholar, and Scopus databases. The authors evaluated each of the selected articles in order to assess the implementation of ImageJ in OCT-A images.

Results

ImageJ can aid in reducing artifacts, enhancing image quality to increase the accuracy of the process and analysis, processing and analyzing images, generating comparable parameters such as the parameters that assess perfusion of the layers (vessel density (VD), skeletonized density (SD), and vessel length density (VLD)) and the parameters that evaluate the structure of the layers (fractal dimension (FD), vessel density index (VDI), and lacunarity (LAC)), and the foveal avascular zone (FAZ) that are used widely in the retinal and choroidal studies), and establishing diagnostic criteria. It can help to save time when the dataset is huge with numerous plugins and options for image processing and analysis with reliable results. Diverse studies implemented distinct binarization and thresholding techniques, resulting in disparate outcomes and incomparable parameters. Uniformity in methodology is required to acquire comparable data from studies employing diverse processing and analysis techniques that yield varied outcomes.

Conclusion

Researchers and professionals might benefit from using ImageJ because of how quickly and correctly it processes and analyzes images. It is highly adaptable and potent software, allowing users to evaluate images in a variety of ways. There exists a diverse range of methodologies for analyzing OCTA images through the utilization of ImageJ. However, it is imperative to establish a standardized strategy to ensure the reliability and consistency of the method for research purposes.

Disagreement of Radial Peripapillary Capillary Density Among Four Optical Coherence Tomography Angiography Devices

Purpose

This prospective study evaluated the agreement among four optical coherence tomography angiography (OCTA) devices in the assessment of radial peripapillary capillary (RPC) density.

Methods

The study included 48 eyes of 48 subjects (14 healthy, 19 glaucomatous, and 15 non-glaucomatous optic neuropathy). Each participant was scanned using four OCTA devices in a random sequence: RTVue XR Avanti (RTVue), DRI OCT Triton (Triton), Revo NX 130 (Revo), and PLEX Elite 9000 (PlexE). All 6 × 6-mm grayscale OCTA images from each device were analyzed for RPC density using a customized algorithm. Agreement between each pair of devices was assessed using intraclass correlation coefficients (ICCs) and Bland-Altman plots.

Results

There was a poor correlation between devices in all comparisons (RTVue-Triton, ICC = 0.34; RTVue-Revo, ICC = 0.31; RTVue-PlexE, ICC = 0.28; Triton-Revo, ICC = 0.31; Triton-PlexE, ICC = 0.17; Revo-PlexE, ICC = 0.34). Significant proportional biases (P < 0.05) and wide limits of agreement with apparent constant biases were identified in all comparisons. The mean difference was greatest for the RTVue-Revo pair (-49.3%; 95% confidence interval [CI], -52.9 to -45.8) and smallest for the Triton-PlexE pair (-7.7%; 95% CI, -10.1 to -5.3).

Conclusions

The RPC densities obtained from each device had poor inter-device agreement and significant biases and cannot be used interchangeably.

Translational Relevance

RPC density obtained from different OCTA devices is not interchangeable; thus, the progression of optic neuropathy should be monitored using the same OCTA device.

Optical coherence tomography angiography biomarkers in a bi-monthly maintenance dosing aflibercept in patients with neovascular age-related macular degeneration

PURPOSE

To evaluate the correlations between swept-source optical coherence tomography angiography (SS-OCTA) parameters and clinical outcomes in eyes with neovascular age-related macular degeneration (nAMD) administered a bimonthly intravitreal aflibercept regimen.

METHODS

This prospective, single-arm, interventional study enrolled 33 patients with treatment-naïve nAMD. The eyes received three monthly aflibercept injections followed by five bi-monthly regimens (total 50 weeks). The structural parameters including central subfield thickness (CST) and 5 mm pigment epithelial detachment (PED) volume and microvascular parameters including macular neovascularization (MNV) area, vessel density (VD), and vessel length density (VLD) were recorded every before and 1 week after treatment.

RESULTS

Patients who gained > 5 letters of best-corrected visual acuity (BCVA) from the baseline showed greater decreases in VD and VLD during the loading phase. Patients without recurrent or persistent fluid during the maintenance phase showed greater decreases in CST and 5 mm PED volume after the first injection. The decrease in mean VD during the loading phase was significantly correlated with the final BCVA (r = -0.820, p = 0.004). Moreover, the decrease in mean VLD during the loading phase was significantly correlated with the improvement in the final BCVA (r = -0.726, p = 0.017).

CONCLUSIONS

The decrease in mean VD during the loading phase was significantly negatively correlated with the final BCVA at the last visit. The decrease in mean VLD during the loading phase, mean CST during the loading phase, and the improvement in final BCVA showed significant correlations. Therefore, early changes in OCTA microvascular and OCT structural parameters could help predict clinical outcomes in nAMD.

TRIAL REGISTRATION

The trial was registered with the Clinical Research Information Service (CRIS), which joined the WHO International Clinical Trials Registry Platform (ICTRP) (Registration number: KCT0007375, Date of first trial registration: 10/06/2022).

Advances in OCT Imaging in Myopia and Pathologic Myopia

Advances in imaging with optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) technology, including the development of swept source OCT/OCTA, widefield or ultra-widefield systems, have greatly improved the understanding, diagnosis, and treatment of myopia and myopia-related complications. Anterior segment OCT is useful for imaging the anterior segment of myopes, providing the basis for implantable collamer lens optimization, or detecting intraocular lens decentration in high myopic patients. OCT has enhanced imaging of vitreous properties, and measurement of choroidal thickness in myopic eyes. Widefield OCT systems have greatly improved the visualization of peripheral retinal lesions and have enabled the evaluation of wide staphyloma and ocular curvature. Based on OCT imaging, a new classification system and guidelines for the management of myopic traction maculopathy have been proposed; different dome-shaped macula morphologies have been described; and myopia-related abnormalities in the optic nerve and peripapillary region have been demonstrated. OCTA can quantitatively evaluate the retinal microvasculature and choriocapillaris, which is useful for the early detection of myopic choroidal neovascularization and the evaluation of anti-vascular endothelial growth factor therapy in these patients. In addition, the application of artificial intelligence in OCT/OCTA imaging in myopia has achieved promising results.

Optical coherence tomography (OCT) angiolytics: a review of OCT angiography quantitative biomarkers

Optical coherence tomography angiography (OCTA) provides a non-invasive method to obtain angiography of the chorioretinal vasculature leading to its recent widespread adoption. With a growing number of studies exploring the use of OCTA, various biomarkers quantifying the vascular characteristics have come to light. In the current report, we summarize the biomarkers currently described for retinal and choroidal vasculature using OCTA systems and the methods used to obtain them. Further, we present a critical review of these methods and key findings in common retinal diseases and appraise future directions, including applications of artificial intelligence in OCTA .

Retinal Flow Density Changes in Early-stage Parkinson's Disease Investigated by Swept-Source Optical Coherence Tomography Angiography

Background: Parkinson's Disease (PD) is the second-most common neurodegenerative disease affecting the elderly population. The eye has been referred to as a window to the brain due to its inseparable relationship with the central nervous system. The development of Swept-Source Optical Coherence Tomography (SS-OCT) and Optical Coherence Tomography Angiography (OCTA) technologies has offered us a better imaging modality to study the impact of PD on the retina.Method: Seventy-five eyes of 42 early-stage PD patients and 150 eyes of 75 matched healthy controls were enrolled in the current study. We performed SS-OCT and SS-OCTA to assess retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) + inner plexiform layer (IPL), internal nuclear layer (INL) thickness, and retinal flow density and flow ratio.Results: Our study indicates decreasing superficial and deep flow density in most regions of the retina. Superficial and deep flow parameters were also associated with RNFL, GCL+IPL, and INL thickness. ROC analysis reveals superficial flow density demonstrated an Area Under Curve (AUC) of 0.688, which is greater than deep flow density and retinal thickness measurements.Conclusion: To the best of our knowledge, we are the first study using SS-OCT and SS-OCTA to study superficial and deep retinal flow changes in early-stage PD patients. Our study suggests decreasing retinal flow density provides greater diagnostic power than retinal thickness measurements in the early stage of PD. SS-OCTA parameters could potentially serve as imaging biomarkers in PD diagnosis and staging.

Comparison of swept-source versus spectral-domain optical coherence tomography angiography for detection of macular neovascularization

Purpose

To compare swept-source (SS) versus spectral-domain (SD) optical coherence tomography angiography (OCTA) for the detection of macular neovascularization (MNV).

Methods

In this prospective cohort study, 72 eyes of 54 patients with subretinal hyperreflective material (SHRM) and/or pigment epithelial detachment (PED) on OCT possibly corresponding to MNV in at least one eye were included. OCTA scans were acquired using two devices, the PLEX Elite 9000 SS-OCTA and the Spectralis SD-OCTA. Fluorescein angiography (FA) was used as reference. Two graders independently evaluated en face OCTA images using a preset slab as well as a manually modified slab, followed by a combination of en face and cross-sectional OCTA.

Results

Sensitivity (specificity) for the automated slabs was 51.7% (93.0%) for SS-OCTA versus 58.6% (95.3%) for SD-OCTA. Manual modification of segmentation increased sensitivity to 79.3% for SS-OCTA but not for SD-OCTA (58.6%). The combination of en face OCTA with cross-sectional OCTA reached highest sensitivity values (SS-OCTA: 82.8%, SD-OCTA: 86.2%), and lowest number of cases with discrepancies between SS-OCTA and SD-OCTA (4.2%). Fleiss kappa as measure of concordance between FA, SS-OCTA, and SD-OCTA was 0.56 for the automated slabs, 0.60 for the manual slabs, and 0.73 (good agreement) for the combination of en face OCTA with cross-sectional OCTA. Concordance to FA was moderate for the automated slabs and good for manual slabs and combination with cross-sectional OCTA of both devices.

Conclusion

Both devices reached comparable results regarding the detection of MNV on OCTA. Sensitivity for MNV detection and agreement between devices was best when evaluating a combination of en face and cross-sectional OCTA.

Optical coherence tomography angiography helps distinguish multiple sclerosis from AQP4-IgG-seropositive neuromyelitis optica spectrum disorder

INTRODUCTION

The aim was to characterize the optical coherence tomography (OCT) angiography measures in patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) and to evaluate their disease discrimination capacity.

METHODS

Patients with MS (n = 83) and AQP4-IgG-seropositive NMOSD (n = 91) with or without a history of optic neuritis, together with healthy controls (n = 34), were imaged. The main outcome measures were peripapillary retinal nerve fiber layer (pRNFL) thickness, macular ganglion cell-inner plexiform layer (GC-IPL) thickness, macular vessel density (VD), and perfusion density (PD) in the superficial capillary plexus. Diagnostic accuracy was assessed using the area under the receiver operating characteristics curve.

RESULTS

Compared with patients with MS, those with NMOSD had a significantly smaller average thickness of the pRNFL and GC-IPL (80.0 [59.0; 95.8] μm versus 92.0 [80.2; 101] μm, p < .001; 68.0 [56.0; 81.0] μm, versus 74.5 [64.2; 81.0] μm, p < .001) and significantly smaller whole VD and PD areas (15.6 [12.6; 17.0] mm^-1 versus 16.7 [14.8; 17.7] mm^-1 , p < .001; 0.38 [0.31; 0.42] mm^-1 versus 0.40 [0.37; 0.43] mm^-1 , p < .01). The combination of structural parameters (average thickness of the pRNFL and GC-IPL) with microvascular parameters (temporal-inner quadrant of VD, temporal-inner, nasal-inferior, and nasal-outer quadrant of PD) was revealed to have a good diagnostic capability for discriminating between NMOSD and MS.

CONCLUSIONS

OCT angiography reveals different structural and microvascular retinal changes in MS and AQP4-IgG-seropositive NMOSD. These combined structural and microvascular parameters might be promising biomarkers for disease diagnosis.

Comparison of macular structural and vascular changes in neuromyelitis optica spectrum disorder and primary open angle glaucoma: a cross-sectional study

AIMS

To compare macular structure and vasculature between neuromyelitis optica spectrum disorder (NMOSD) and primary open angle glaucoma (POAG) using optical coherence tomography angiography.

METHODS

NMOSD patients (n=124) with/without a history of optic neuritis (ON) (NMO+ON: 113 eyes; NMO-ON: 95 eyes), glaucomatous patients (n=102) with early/advanced glaucoma (G-E: 74 eyes; G-A: 50 eyes) and healthy controls (n=62; 90 eyes) were imaged. The main outcome measures were macular ganglion cell-inner plexiform layer (GC-IPL) thickness, vessel density (VD) and perfusion density (PD) in the superficial capillary plexus, and diagnostic capabilities of the parameters as calculated by area under the curve (AUC).

RESULTS

Significant losses in GC-IPL, VD and PD were detected in both patients with NMOSD and POAG. With matched losses in the peripapillary retinal nerve fibre layer, NMOSD group showed significant thinning of GC-IPL in the nasal-superior quadrant, whereas in POAG group, significant thinning was observed in the inferior and temporal-inferior quadrants. GC-IPL thinning was more prominent in the superior, nasal-superior and nasal-inferior quadrants in NMO+ON eyes. In G-A eyes, significant GC-IPL thinning was seen in the temporal-inferior quadrant. The specific structural parameters combining VD and foveal avascular zone (FAZ) indices showed the best diagnostic accuracies. The FAZ area in eyes with NMOSD was significantly smaller than the eyes of healthy controls and POAG.

CONCLUSION

NMOSD and POAG have specific patterns of macular structural and vascular changes associated with pathophysiology. Our results indicate that FAZ could be a sensitive biomarker of macular changes in NMOSD.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Treatment-naïve quiescent macular neovascularization secondary to AMD: The 2019 Young Investigator Lecture of Macula Society

PURPOSE

To analyze different clinical and anatomical features in treatment-naïve non-exudative macular neovascularizations (MNVs) secondary to age-related macular disease (AMD).

METHODS

In this retrospective longitudinal study with a minimum follow-up of 1 year, 31 eyes of 28 consecutive AMD patients (mean age 75 ± 9 years) with treatment-naïve non-exudative MNV were enrolled. Patients were divided in: short-term activated MNV group (exudation before 6-month) and quiescent MNV group (per definition no exudation during a minimum 6-month follow-up) showing no or late activation during follow-up (persistently quiescent and long-term activated MNV group, respectively).

RESULTS

During the follow-up (mean duration: 22 ± 9 months) four eyes (13%) showed exudation before 6-month follow-up (short-term activated MNV group), whereas 21 eyes (68%) did not develop signs of exudation (persistently quiescent group), and six eyes (19%) developed exudation after the minimum 6-month follow-up (long-term activated MNV group). Monthly MNV growth rate was significantly higher in the short-term activated MNV group (growth rate of 13.30%/month), vs persistently quiescent MNV group (0.64%/month, p < 0.001) and long-term activated quiescent MNV group (1.07%/month, p < 0.001). Furthermore, at the baseline, perfusion density of short-term activated MNV group was significantly greater in comparison to persistently quiescent MNV group (p = 0.001) and long-term activated MNV group (p = 0.106).

CONCLUSION

We reported two different patterns for subclinical MNVs: subclinical MNVs characterized by short-term activation which could represent simply a pre-exudative stage in the development of an ordinary type 1 MNV, and quiescent MNVs characterized by low rate of growth and possible long-term activation. Analysis of OCT-A features may predict short-term activation for subclinical MNV but no features could predict the long-term activation.

Foveal Avascular Zone Measurement Via Optical Coherence Tomography Angiography and its Relationship With the Visual Field in Eyes With Open-angle Glaucoma

PRECIS

The foveal avascular zone (FAZ) in optical coherence tomography angiography is significantly correlated with retinal inner layer thickness, Humphrey field analyzer (HFA) 10-2 sensitivity threshold, and mean deviation (MD) value in open-angle glaucoma patients.

PURPOSE

The purpose of this study was to measure the FAZ area using optical coherence tomography angiography and investigate its relationship with retinal inner layer thickness and visual field defects in eyes with open-angle glaucoma.

PARTICIPANTS AND METHODS

A total of 52 eyes with open-angle glaucoma from 52 patients. FAZ area was measured using optical coherence tomography angiography in angio-macula mode. Thicknesses of retinal nerve fiber layer (RNFL), ganglion cell layer plus inner plexiform layer (GCL+IPL), and ganglion cell complex (GCC) were determined using a 7 mm×7 mm macular (V) map via 3D-OCT. Correlations of FAZ area with sensitivity threshold measurements, foveal threshold (FT), and MD value in the HFA10-2 visual field were analyzed for each inner retinal layer.

RESULTS

FAZ area was 0.26±0.07 mm; overall mean thicknesses were 19.14±6.55 μm (RNFL), 57.34±5.93 µm (GCL+IPL), and 75.87±10.96 μm (GCC); mean FT was 35.23±3.15 dB, and sensitivity threshold was 20.81±7.22 dB in the HFA10-2 visual field. FAZ area was significantly correlated with the thickness of individual retinal layers in the entire field (RNFL, P<0.001; GCL+IPL, P<0.001; GCC, P<0.001), sensitivity threshold (P=0.01), FT (P<0.001), and MD value (P=0.011).

CONCLUSION

FAZ area was significantly negatively correlated with retinal inner layer thickness, sensitivity threshold, FT, and MD value in the HFA10-2 visual field.

Quantitative Comparison of the Vascular Structure of Macular Neovascularizations Between Swept-Source and Spectral-Domain Optical Coherence Tomography Angiography

Purpose

The aim of this study was to ascertain and quantify the differences between swept-source (SS) and spectral-domain (SD) optical coherence tomography angiography (OCTA) imaging of macular neovascularizations (MNV) in neovascular age-related macular degeneration (nAMD).

Patients and Methods

SD-OCTA (RTVue Avanti) and SS-OCTA (PLEX^® Elite 9000) were performed in 37 patients with MNV in nAMD. The MNV was delineated and the data were processed via ImageJ. The parameters MNV area, nodes per area, fractal dimension (FD), and flow density were analyzed using MatLab.

Results

There was close agreement between the two devices regarding MNV area (ICCc 0.977, ICCa 0.977, R² 0.977), but only slight agreement regarding nodes per area (ICCa 0.008, ICCc 0.548, R² 0.51), FD (ICCa 0.425, ICCc 0.846, R² 0.96), and flow density (ICCa 0.451, ICCc 0.656, R² 0.65). The difference between the two devices was insignificant for MNV area (type 1: p=0.328; type 2: p=0.426; type 3: p=0.615), but significant for nodes per area (type 1: p=0.002; type 2: p=0.00001; type 3: p=0.003), FD (type 1: p<0.00001; type 2: p<0.00001; type 3: p=0.015) and flow density (type 1: p=0.0004; type 2: p=0.004; type 3: p=0.052).

Conclusion

MNV area is closely comparable between devices using SS-OCTA and SD-OCTA imaging. However, the two methods differ significantly in their precise assessment of the vascular morphology (FD, flow density, nodes per area). Therefore, results obtained using different devices are not comparable and should not be amalgamated in clinical trials.

A quantitative comparison of four optical coherence tomography angiography devices in healthy eyes

PURPOSE

Optical coherence tomography angiography (OCT-A) is a novel imaging modality for the diagnosis of chorioretinal diseases. A number of FDA-approved OCT-A devices are currently commercially available, each with unique algorithms and scanning protocols. Although several published studies have compared different combinations of OCT-A machines, there is a lack of agreement on the consistency of measurements across OCT-A devices. Therefore, we conducted a prospective quantitative comparison of four available OCT-A platforms.

METHODS

Subjects were scanned on four devices: Optovue RTVue-XR, Heidelberg Spectralis OCT2 module, Zeiss Plex Elite 9000 Swept-Source OCT, and Topcon DRI-OCT Triton Swept-Source OCT. 3 mm × 3 mm images were utilized for analysis. Foveal avascular zone (FAZ) area was separately and independently measured by two investigators. Fractal dimension (FD), superficial capillary plexus (SCP), and deep capillary plexus (DCP) vessel densities (VD) were calculated from binarized images using the Fiji image processing software. SCP and DCP VD were further calculated after images were skeletonized. Repeated measures ANOVA, post hoc tests, and interclass correlation coefficient (ICC) were performed for statistical analysis.

RESULTS

Sixteen healthy eyes from sixteen patients were scanned on the four devices. Images of five eyes from the Triton device were excluded due to poor image quality; thus, the authors performed two sets comparisons, one with and one without the Triton machine. FAZ area showed no significant difference across devices with an ICC of > 95%. However, there were statistically significant differences for SCP and DCP VD both before and after skeletonization (p < 0.05). Fractal analysis revealed no significant difference of FD at the SCP; however, a statistically significant difference was found for FD at the DCP layer (p < 0.05).

CONCLUSIONS

The results showed that FAZ measurements were consistent across all four devices, while significant differences in VD and FD measurements existed. Therefore, we suggest that for both clinical follow-up and research studies, FAZ area is a useful parameter for OCT-A image analysis when measurements are made on different machines, while VD and FD show significant variability when measured across devices.

Different Effect of Media Opacity on Vessel Density Measured by Different Optical Coherence Tomography Angiography Algorithms

Purpose

Several studies show that media opacity reduces vessel density (VD) measured by image processing algorithms of optical coherence tomography angiography (OCTA). However, different models of OCTA designed their own algorithms and computational methods, which may have different effects of opacity on VD. This study is aimed to investigate the impact of a simulated model of media opacity on quantitative measurement of two OCTA devices.

Methods

A spectral-domain based OCTA (Cirrus 5000; Carl Zeiss Meditec) and a swept-source based OCTA (Triton DRI-OCT, Topcon Inc.) were used to image retinal microvasculature at the macula using 3 × 3 mm scanning protocol from 22 eyes of 22 healthy subjects. Media opacity was simulated with neutral-density filters (optical density (OD)_λ=840nm ranges 0.10-0.48 in Cirrus; OD_λ=1050nm ranges 0.15-0.51 in Triton). The filters were placed in front of each study eye, and signal strength (SS) or signal strength intensity (SSI) was recorded during imaging. The parafoveal VD of superficial capillary plexus was then measured using the built-in software from the two devices. The correlations among OD, SS/SSI, and VD were analyzed.

Results

Increased OD was significantly correlated with decreased SS and SSI (r_s = -0.576 and -0.922, respectively, both P < 0.001) in Cirrus and Triton, respectively. Although increased OD was significantly correlated with decreased VD in Cirrus (r_s = -0.539, P < 0.001), there was no significant correlation between OD with VD in Triton (r_s = -0.143, P = 0.137).

Conclusions

The effect of media opacity on quantitative measurement of VD is different between different Cirrus and Triton OCTA devices.

Translational Relevance

This study demonstrates that the effect of media opacity on VD measurement is different among different OCTA devices, suggesting that caution must be taken when interpreting VD measurement on OCTA, particularly among individuals with media opacity.

Appearance of cysts and capillary non perfusion areas in diabetic macular edema using two different OCTA devices

The aim of this paper was to distinguish the appearance of cysts and non-perfusion areas (NPAs) in diabetic macular edema (DME) using two different Optical Coherence Tomography Angiography (OCTA) devices. In this study, patients underwent OCTA using the AngioVue XR Avanti Spectral Domain (SD) OCTA and the PLEX Elite 9000 Swept-Source (SS) OCTA. Foveal and extrafoveal regions of interest (ROI), defined as any area with an altered flow signal comparing to the surrounding retina, were selected in superficial and deep capillary plexus (SCP and DCP). ROI reflectivity were classified as hypo-reflective or hyper-reflective. Foveal ROI were analyzed to detect suspended scattering particles in motion (SSPiM). Thirty-seven DME eyes were included. A larger number of ROIs were found in SCP (55 vs 39) and DCP (60 vs 49) using PLEX Elite 9000 vs AngioVue. The majority of ROIs were hypo-reflective with both instruments, while slightly more hyper-reflective ROIs (grey) were detected with the PLEX Elite, more likely to be cysts. The hyporeflective ROIs could be NPAs or cysts with both devices. Moreover, PLEX Elite 9000 identified SSPiM in more foveal ROIs than the AngioVue in the SCP (p = 0.005) and in the DCP (p = 0.027). In conclusion, NPAs and cysts may show variable appearances using different OCTA devices. Hyperreflective ROIs generally correspond to cysts, hyporeflective ROIs can be either cysts or NPAs. The SS-OCTA seems to detect SSPiM more frequently than the SD-OCTA.

Noninvasive Structural Imaging of a Retinal Cavernous Hemangioma Using SS-OCTA and Correlation to Previously Reported Histopathology

Optical coherence tomography angiography (OCTA) is a novel imaging modality, and its role in the clinical evaluation of patients remains to be defined. In this report, the authors describe a case of a retinal cavernous hemangioma and show that OCTA of the lesion recapitulates many structural features first described in previous histopathologic studies, including aneurysmal architecture, septated blood flow, and epiretinal membrane. Thus, OCTA provides a new, noninvasive means of studying retinal cavernous hemangioma structure, a unique capability that may also be clinically relevant to the evaluation of other pathologic retinal vascular tumors, such as capillary and racemose hemangiomas. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e320-e323.].