Impact of correct anatomical slab segmentation on foveal avascular zone measurements by optical coherence tomography angiography in healthy adults

Clinical Features Related to OCT Angiography Artifacts in Patients with Diabetic Macular Edema

PURPOSE

To investigate the frequency and type of artifacts on OCT angiography (OCTA) images and the relationship with clinical features in eyes with diabetic macular edema (DME).

DESIGN

Retrospective, cross-sectional comparative study.

SUBJECTS

One hundred ninety-two eyes of 140 patients with DME were included.

METHODS

Medical records, OCT and OCTA images (Spectralis), and ultrawidefield color fundus photographs (Optos plc) were evaluated.

MAIN OUTCOME MEASURES

The frequency of artifact types (segmentation, motion, projection artifact, and low signal) was determined. The relationships between artifact types and clinical features such as best-corrected visual acuity (BCVA), mean central retinal thickness (CRT), foveal avascular zone (FAZ) area, perimeter, circularity index, perfusion density (PD), vessel density (VD), fractal dimension (FD) in the superficial capillary plexus, intermediate capillary plexus (ICP), and deep capillary plexus (DCP), flow voids (FVs) in the choriocapillaris, presence of hard exudate (HE), and cataract were determined.

RESULTS

The mean age was 71.6 ± 11.4 years, and 86 (61.4%) out of 140 were men. Artifacts were present in 63 (32.8%) of 192 eyes. Twenty-nine (15.1%) eyes had segmentation artifacts, 12 (6.3%) had motion artifacts, 11 (5.7%) had projection artifacts, and 18 (9.4%) had low signal. Best-corrected visual acuity, PD, VD, and FD in ICP and DCP were significantly lower; and CRT, FAZ area and perimeter in ICP and DCP, and presence of cystoid macular edema, HE, and cataract were higher in eyes with artifacts versus eyes without artifacts (P < 0.05 for each). Multivariate linear regression analysis showed a significant association between segmentation artifacts and decreased BCVA (odds ratio [OR], 5.277; P = 0.02), increased CRT (OR, 1.015; P < 0.001), increased area of FAZ in DCP (OR, 6.625; P = 0.02), and increased perimeter of FAZ in DCP (OR, 1.775; P < 0.04); there was also a significant association between projection artifacts and presence of HE (OR, 2.017; P = 0.02) and between motion artifacts and presence of cataract (OR, 4.102; P = 0.01).

CONCLUSIONS

OCT angiography artifacts were present in one third of DME eyes, with segmentation artifacts being the most frequent type. Determining OCTA artifacts is crucial to ensure accurate clinical evaluation. These data could help in developing more standardized clinical protocols for image acquisition and interpretation used in clinical practice and research.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Analysis of Choriocapillaris Reperfusion Topography Following Faricimab Treatment for Neovascular Age-Related Macular Degeneration in Therapy-Naïve Patients

INTRODUCTION

To assess changes in choriocapillaris (CC) vascular density surrounding macular neovascularization (MNV) in treatment-naïve age-related macular degeneration (AMD) after faricimab application using optical coherence tomography angiography (OCTA).

METHODS

Twenty-five eyes of 25 treatment-naïve individuals who underwent intravitreal faricimab injections for neovascular AMD (nAMD) with type 1 MNV were included. Spectral-domain optical coherence tomography (SD-OCT) images and en-face swept-source OCTA images were analyzed, and the percentage of CC flow deficit (FD%), FD average area (FDa) and FD number (FDn) in five progressive 20.0-μm-wide concentric rings (R1, R2, R3, R4 and R5) surrounding the dark halo around the MNV were calculated. Image acquisition was carried out prior to the first faricimab injection (T0) and 1 month after the injection (T1).

RESULTS

The topographical sub-analysis revealed noteworthy changes in all rings at T1 compared to T0. There was a notable progressive reduction in FD% at T1 compared to T0 values across all rings, indicating a gradual CC reperfusion following anti-VEGF treatment. Additionally, the average size of FD decreased after the loading phase. Although not reaching statistical significance, there was a progressive reduction in the FDa across all rings.

CONCLUSION

Our study highlights a CC FD reduction following the administration of three consecutive faricimab injections. This effect was detected in all rings surrounding the dark halo. These observations suggest a partial CC reperfusion surrounding the MNV, potentially serving as an indicator for disease regression.

Analysis of Choriocapillaris Reperfusion Topography following Faricimab Treatment for Neovascular Age-Related Macular Degeneration in Non-Treatment-Naïve Patients

To assess changes in choriocapillaris (CC) vascular density surrounding macular neovascularization (MNV) in age-related macular degeneration (AMD) when transitioning from various anti-VEGF treatments to faricimab, using optical coherence tomography angiography (OCTA). 25 eyes of 22 individuals who underwent intravitreal faricimab injections for neovascular AMD with type 1 MNV were included. OCTA images were obtained prior to (T0), after one (T1), and after three faricimab injections (T2); Noteworthy changes occurred in the first ring at T2 in comparison to T0. The percentage of CC flow deficit (FD%), FD average area (FDa), and FD number (FDn) in 5 rings (R1-R5) surrounding the dark halo around the MNV were calculated. A reduction in FD% at T2 compared to T0 (50.5 ± 10.2% at T0, 46.4 ± 10.6% at T2; p = 0.020) was seen, indicating CC reperfusion. Additionally, we observed a reduction in the average FDa (140.2 ± 172.1% at T0, 93.7 ± 101.8% at T2; p = 0.029). Our study highlights an FD% after three consecutive faricimab injections. The most pronounced effect was observed in the first ring, directly adjacent to the dark halo, suggesting a partial CC reperfusion surrounding the MNV, potentially indicating disease regression.

Evaluation of retinal microvascular network in patients with systemic sclerosis: An optical cohorence tomography angiography study

PURPOSE

To investigate the long-term effect of systemic sclerosis on the optic disk and retinal capillary network and to see whether the drugs used in the treatment of SSc affected optical coherence tomography angiography (OCTA) parameters.

MATERIALS AND METHODS

This cross-sectional case-control study included 40 systemic sclerosis patients and 40 healthy individuals. We included only one eye of each patient in the study. Macular layers and angiography scanning were performed with a Zeiss Cirrus 5000 OCTA system. Such values as macular thickness, retinal nerve fiber layer (RNFL), ganglion cell inner plexiform layer (GC-IPL) were obtained. For central vessel and perfusion density (VD, PD), central 6 mm were obtained and were evaluated by dividing it into 3 groups as inner, outer, and full. The FAZ was evaluated through 3 parameters: area, perimeter, circularity index.

RESULTS

Statistically significant difference was found between the groups in terms of the mean and foveal macular thickness values (p=0.008, p=0.033). Significant differences were also found between the two groups in terms of the VD and PD parameters in all regions except for 1 mm center (p<0.05). There were no significant differences in RNFL and GC-IPL values between two groups. Also, a positive correlation was observed between parapapillary perfusion density values and RNFL and GC-IPL thicknesses in SSc group. When the subgroups were compared in terms of vasodilator drug use, the subgroup using vasodilators was seen to have higher mean RNFL and inferior RNFL thicknesses (p=0.045 and p=0.035, respectively). In addition, there was a significant positive correlation between parapapillary VD and RNFL values in the SSc subgroup treated with vasodilators.

CONCLUSIONS

The results of this study demonstrate microvascular loss in individuals with systemic sclerosis, compared with healthy subjects. Also, it has been determined that OCTA is an important test for screening retinal and optic disk microvascular changes over time in cases of systemic sclerosis and may be used to evaluate the response to vasodilator drugs used in the treatment of SSc disease.

Optical Coherence Tomography Angiography Is a Useful Tool for Distinguishing Primary Raynaud's Phenomenon from Systemic Sclerosis and/or Very Early Disease of Systemic Sclerosis

This cross-sectional study aimed to compare optical coherence tomography angiography (OCT-A) findings in patients with primary Raynaud's phenomenon (PRP; n = 22), very early disease of systemic sclerosis (VEDOSS; n = 19), and systemic sclerosis (SSc; 25 patients with limited cutaneous SSc (lcSSc) and 13 patients with diffuse cutaneous SSc (dcSSc)). Whole, parafoveal, and perifoveal superficial capillary plexus (SCP) vessel densities (VDs), deep capillary plexus VDs, and whole, inside, and peripapillary VDs were significantly higher in the PRP group (p < 0.001). In the lcSSc group, the FAZ perimeter was significantly higher than that in the VEDOSS group (p = 0.017). Retinal nerve fiber layer VDs were significantly lower in the lcSSc group than in the PRP and VEDOSS groups (p < 0.001). The whole and peripapillary optic disc VDs of the VEDOSS group were significantly higher than in the lcSSc group (p < 0.001). Whole SCP VDs (94.74% sensitivity, 100.00% specificity) and parafoveal SCP VDs (89.47% sensitivity, 100.00% specificity) showed the best performance in distinguishing patients with SSc from those with PRP. OCT-A seems to have potential diagnostic value in differentiating patients with PRP from patients with SSc and VEDOSS, and there is potential value in assessing prognostic roles, since findings from OCT-A images could be early indicators of retinal vascular injury long before overt SSc symptoms develop.

Ocular complications of diabetes mellitus in a pediatric population and proposals for screening and follow-up programs

Background

Diabetes mellitus (DM) is one of the world's greatest health emergencies of the 21st century. Ocular complications of DM are commonly chronic and progressive, but vision loss can be effectively prevented or delayed with early detection and timely treatment. Therefore, regular comprehensive ophthalmologic examinations are mandatory. Ophthalmic screening and dedicated follow-up for adults with DM are well established, whereas, there is no consensus on optimal recommendations for the pediatric population, reflecting the lack of clarity about the current burden of disease in this age group.

Objectives

To determine the epidemiology of ocular complications of diabetes and to assess optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) macular features in a pediatric population with DM. To review ophthalmological screening and follow-up plans for the diabetic pediatric population.

Design

Observational study.

Methods

Retrospective consecutive cohort study of all 165 diabetic patients (330 eyes) aged 0-18 years, examined between January 2006 and September 2018 at the Pediatric Department of 'S. Maria della Misericordia' Udine Hospital who underwent at least one complete ophthalmologic examination at the Ophthalmology University Clinic at the Udine Hospital. OCT and OCTA data were available for 37 patients (72 eyes, 2 excluded). The associations between ocular complications and selected potential risk factors were evaluated by univariate analyses.

Results

No patient had signs of ocular diabetic complications or any macular morphological or micro-vascular impairment, regardless of any potential risk factor. The prevalence of strabismus and refractive errors in the study group, was found to be similar to non-diabetic pediatric populations.

Conclusion

Screening and follow-up of ocular diabetic complications in children and adolescents could be performed less frequently than in adults with diabetes. There is no need to screen potentially treatable visual disorders in diabetic children earlier or more frequently than in the healthy children thus reducing time spent in hospital and permitting a better tolerance to medical examinations in diabetic pediatric patients. We described the OCT and OCTA patterns in a pediatric population with DM.

Impact of Silicone Oil Removal on Macular Perfusion

(1) Background: Silicone oil (SO) can be used as an endotamponade during vitreoretinal surgery for retinal detachment. There is emerging evidence that SO filling of the vitreous cavity and its removal may impact macular perfusion. So far, studies have not focused on choroidal sublayer perfusion, yet. (2) Methods: Optical coherence tomography angiography was applied in 19 patients with SO endotamponade before and four weeks after removal of SO. (3) Results: Perfusion of choriocapillaris increased significantly after SO removal, while perfusion of Haller’s and Sattler’s layer decreased significantly. (4) Conclusions: Removal of SO impacts choroidal perfusion and leads to a perfusion shift within choroidal sublayers. This study underlines that it is worth to conduct larger prospective studies that evaluate the choroidal perfusion and its functional implications in more detail.

Normative Data of Superficial Retinal Vascular Plexus and the Relationship to Retinal Layers

Objectives:

The aim of this study was to evaluate the relationship between optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) parameters in a healthy population and to detect any changes that occur with age.

Methods:

A total of 100 healthy participants were included in this prospective, observational, and comparative study. The participants were categorized in 4 groups according to age: Group 1: 21-30 years, Group 2: 31-40 years, Group 3: 41-50 years, Group 4: 51-60 years of age. Mean macular thickness, retinal nerve fiber layer (RNFL), ganglion cell inner plexiform layer (GC-IPL), and the choroidal thickness (ChT), vessel density (VD), perfusion density (PD), foveal avascular zone (FAZ), and parapapillary perfusion density parameters were recorded and analyzed.

Results:

In comparisons between groups, no significant difference in OCTA parameters was observed. There were inverse correlations between the outer VD, PD, and intraocular pressure (IOP) (r= -0.307, p=0.006 and r= -0.284, p=0.011, respectively). The correlation between parapapillary perfusion density and IOP was close to being significant (r= -0.213, p=0.059). There were significant relationships between OCTA parameters and macular, RNFL, and GC-IPL thickness. No significant relationship between ChT and OCTA parameters was seen.

Conclusion:

The size and characteristics of superficial VD, PD, parapapillary perfusion density, and FAZ were determined in a population with standardized demographic and ocular clinical features, and the relationship between these parameters and retinal layers was established.

Analysis of choroidal thickness in patients with proliferative diabetic retinopathy by optical coherence tomography angiography

Objectives:

This study aimed to evaluate the changes in choroidal thickness at different parts in patients with stage IV-V diabetic retinopathy (DR) treated by Panretinal Photocoagulation (PRP) or its combination with anti-vascular endothelial growth factor (VEGF) therapy using optical coherence tomography angiography (OCTA).

Methods:

Patients with proliferative DR (stage IV-V) diagnosed in Shijiazhuang People’s Hospital between January 2016 to January 2020 were selected and treated with conventional PRP or combined with anti-VEGF therapy. OCTA was performed before treatment and one three and six months after treatment to observe and compare subfoveal choroidal thickness (SFCT), perifoveal choroidal thickness at 500 um (M500) and 1500 um (M1500).

Results:

A total of 76 patients (133 eyes) were included. Six months later, re-examination showed effective treatment in 122 eyes (91.72%) and ineffective treatment in 11 eyes. Before treatment and one week, three months and six months after treatment, the choroidal thickness was observed and compared by OCTA. SFCT, M500 and M1500 increased one week after treatment, were significantly thinner 3 months after treatment than those before treatment, and further decreased six months after treatment.

Conclusion:

OCTA presents a good evaluation of perifoveal choroidal thickness in patients with proliferative DR. It provides a basis for treatment selection and efficacy determination of proliferative DR.

Assessing the Use of Incorrectly Scaled Optical Coherence Tomography Angiography Images in Peer-Reviewed Studies: A Systematic Review

Importance

Individual differences in axial length affect the lateral magnification of in vivo retinal images and as a result can affect the accuracy of quantitative measurements made from these images. As measurements from optical coherence tomography angiography (OCTA) images are becoming increasingly used in the diagnosis and monitoring of a wide range of diseases, evaluating which studies use correctly scaled images is crucial to their interpretation.

Objective

To perform a systematic literature review to assess the percentage of articles that report correcting the scale of their OCTA images for individual differences in retinal magnification.

Evidence Review

A PubMed (MEDLINE) search was conducted for articles on OCTA retinal imaging published between June 1, 2015, and June 1, 2018. Initial results included 7552 articles. Initial exclusion criteria removed studies of animal models, as well as reviews, letters, replies, comments, and image-based or photographic essays. Articles not written in English and those that required purchase from non-English language websites were excluded. Articles that did not use OCTA for imaging the retina were also excluded. Remaining articles were reviewed in detail to assess whether the OCTA measurements required correct lateral scaling, and if so, whether axial length was reported or used to scale the images. We also determined the number of articles that mentioned the lack of correct lateral scaling as a limitation of the study.

Findings

A total of 989 articles were included in the detailed review. Of these, 509 were determined to require correct image scaling for their analyses, but only 41 (8.0%) report measuring and using axial length to correct the lateral scale of their OCTA images. Furthermore, of the 468 articles that did not correctly scale their images, only 18 (3.8%) mentioned this as a limitation to their study.

Conclusions and Relevance

These findings suggest that most peer-reviewed articles in PubMed that use quantitative OCTA measurements use incorrectly scaled images. This could call into question the conclusions of such studies and warrants consideration by OCTA manufacturers, physicians, authors, journal reviewers, and journal editors.

Influence of Retinal Microsecond Pulse Laser Treatment in Central Serous Chorioretinopathy: A Short-Term Optical Coherence Tomography Angiography Study

Background: Central serous chorioretinopathy (CSC) is a common macular condition characterized by detachment of the neuroretina and is a frequent cause of central vision loss in adults. Among the various therapeutic strategies, subthreshold microsecond pulsed laser (SML) treatment has become a useful option. Despite the suggested involvement of choroidal circulatory disturbances in CSC, the effects of this treatment on macular microperfusion have not been fully evaluated yet. Herein, we report the impact of SML on retinal and choroidal microvascular flow using non-invasive optical coherence tomography (OCT) angiography (OCTA). Methods: In this study, CSC patients with persistent subretinal fluid (SRF) with or without secondary choroidal neovascularization (CNV) were included (referred to as the pachychoroid neovasculopathy (PNV) group and the CSC group, respectively). SML was conducted using a yellow (577 nm) laser with a duty cycle of 10%, spot size of 200 µm and duration of 200 ms. Best corrected visual acuity (BCVA) as well as OCT and OCTA images were evaluated at baseline and 4 weeks after SML. OCTA parameters of interest included full retinal perfusion (FRP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP), and Haller’s layer perfusion (HLP), which were evaluated longitudinally and compared to unaffected fellow eyes. Results: 27 affected eyes and 17 fellow eyes from 27 patients were included. Before treatment, central retinal thickness (CRT) and subfoveal choroidal thickness (SFCT) of affected eyes were significantly larger than in fellow eyes. Four weeks after SML, CRT decreased significantly, whereas perfusion parameters did not change. In subgroup analyses, the CSC group showed a significant decrease in SFCT, whereas the PNV group did not despite the decrease in CRT. Conclusion: Our results suggest that the SML may affect the SFCT of the CSC, but not the PNV patients at least within four weeks following treatment. This effect seems to be independent of the change in choroidal perfusion measured with OCTA.

Quantitative assessment and determinants of foveal avascular zone in healthy volunteers

Objectives

To evaluate the foveal avascular zone (FAZ) area in healthy volunteers using optical coherence tomography angiography (OCTA) and identify factors that influence the FAZ.

Methods

This single-center cross-sectional study included 526 eyes of 263 healthy volunteers who underwent macular scanning by Zeiss OCTA. A linear mixed model was used to investigate the effects of systemic factors (age, sex, blood pressure, height, and weight) and ocular factors (intraocular pressure, biometric parameters, and central macular thickness) on FAZ.

Results

In total, 520 eyes of 262 healthy volunteers were included in the analysis. The mean volunteer age was 38.59 ± 22.03 years (range, 5–84 years); 124 volunteers were male (47.33%) and 138 volunteers were female (52.67%). The mean FAZ area was 0.30 ± 0.03 mm² (95% confidence interval [CI], 0.29–0.31 mm²). Univariate analysis showed that FAZ area was associated with age (β = 0.0011), anterior chamber depth (β = −0.0513), and axial length (β = −0.0202). Multivariate analysis showed that FAZ area was negatively correlated with axial length (β = −0.0181).

Conclusions

The mean FAZ area in healthy volunteers, measured using Zeiss OCTA, was 0.30 ± 0.03 mm². Furthermore, FAZ area was negatively associated with axial length; this relationship should be considered in clinical practice.

Evaluating Retinal and Choroidal Perfusion Changes after Isometric and Dynamic Activity Using Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is a non-invasive tool for imaging and quantifying the retinal and choroidal perfusion state in vivo. This study aimed to evaluate the acute effects of isometric and dynamic exercise on retinal and choroidal sublayer perfusion using OCTA. A pilot study was conducted on young, healthy participants, each of whom performed a specific isometric exercise on the first day and a dynamic exercise the day after. At baseline and immediately after the exercise, heart rate (HR), mean arterial pressure (MAP), superficial capillary plexus perfusion (SCPP), deep capillary plexus perfusion (DCPP), choriocapillaris perfusion (CCP), Sattlers’s layer perfusion (SLP), and Haller’s layer perfusion (HLP) were recorded. A total of 34 eyes of 34 subjects with a mean age of 32.35 ± 7.87 years were included. HR as well as MAP increased significantly after both types of exercise. Both SCPP and DCPP did not show any significant alteration due to isometric or dynamic exercise. After performing dynamic exercise, CCP, SLP, as well as HLP significantly increased. Changes in MAP correlated significantly with changes in HLP after the dynamic activity. OCTA-based analysis in healthy adults following physical activity demonstrated a constant retinal perfusion, supporting the theory of autoregulatory mechanisms. Dynamic exercise, as opposed to isometric activity, significantly changed choroidal perfusion. OCTA imaging may represent a novel and sensitive tool to expand the diagnostic spectrum in the field of sports medicine.

Evaluation of the direct effects on retinal and choroidal microvascularity of systemic scleroderma

OBJECTIVE

Ocular involvement in systemic sclerosis (SSc) has been documented; however it cannot be distinguished from secondary changes due to concomitant hypertension.Therefore, the aim of this prospective cross-sectional study was to demonstrate the direct effects of Ssc on retinal and choroidal microvasculature in patients without hypertension.

METHODS

47 SSc patients and 44 age- and sex-matched healthy control subjects were enrolled in this study. In fundus examination: Increased vascular tortitis, focal or general arteriolar narrowing, arteriovenous notch, severe exudation, microhemorrhage, and pigment epithelial changes in the retina of SSc patients without hypertension were investigated. Patients with at least two of the above findings were considered to have retinopathy After that, patients were divided into two groups according to the presence of retinopathy in this study. Retinal and choroidal microvasculature were evaluated using optical coherence tomography angiography.

RESULTS

There was a significant decrease in SSc patients with retinopathy in both superficial capillary plexus vessel density (SCP VD) and deep capillary plexus vessel density (DCP VD) compared to the control group. Full avascular zone (FAZ) evaluation tool variables (FAZ area, FAZ perimeter, foveal density) were significantly lower in all Ssc patients than in the healthy control group. It was found that the flow in the 1 mm and 3 mm circular area (Outer Retina 1-3 mm Flow Area) increased significantly in Ssc patients with retinopathy. Choroidal flow (Choriocapillaries 1 mm Flow Area) was statistically lower in Ssc patients with retinopathy.

CONCLUSIONS

We have showed an increase in the outer retina 1-3 mm flow area (circular area of the outer retina fold covering the fovea) despite the decrease in vascular density and choroidal thickness in scleroderma patients with retinopathy. Hence, we first demonstrated that Ssc itself may have an effect on retinal and choroidal microvasculature, independent of hypertension.

Applicability of optical coherence tomography angiography (OCTA) imaging in Parkinson's disease

To evaluate the significance of motion artifacts in optical coherence tomography angiography (OCTA) images of patients with Parkinson’s disease (PD) and healthy controls. In this prospective, cross-sectional study subjects with medicated PD (ON) and healthy, age- and gender-matched volunteers were recruited. Participants underwent specific ophthalmological examinations, including OCTA. Angiograms of the superficial retinal capillary plexus were evaluated for the type and frequency of artifacts using a validated motion artifact score (MAS). A total of 30 PD patients (60 eyes), average disease duration of 9.61 ± 5.55 years, and 30 matched, healthy controls (60 eyes) were recruited. Twenty percent of all eyes had an eye disease, unknown to the participant, with a significant impact on OCTA results. After cleansing the dataset by excluding subjects with confounding ocular comorbidities 42 eyes of 28 PD patients and 53 eyes of 29 healthy controls were further evaluated. Overall MAS and all five subtypes of motion artifacts were comparable without significant differences between groups. OCTA can be used in treated PD patients (ON) without a significant increase in motion artifacts. Nevertheless, special attention should be paid to image quality during the acquisition of OCTA data, for which an experienced OCTA operator is useful.

Correlation of retinal and choroidal microvascular impairment in systemic sclerosis

Purpose

To investigate the correlation between retinal and choroidal microperfusion in patients with systemic sclerosis (SSc) using optical coherence tomography angiography (OCTA).

Methods

In this cross-sectional study SSc patients without clinical evidence of ocular involvement and healthy, age- and sex-matched volunteers were recruited. Participants underwent specific rheumatological and ophthalmological examinations, including optical coherence tomography (OCT) and OCTA. Retinal and choroidal thicknesses as well as perfusion of the retina and the choroidal sublayers were evaluated.

Results

A total of 15 SSc patients (30 eyes) with a median disease duration of 60 months and 15 matched, healthy controls (30 eyes) were recruited. OCT data revealed a significantly lower macular volume, as well as Sattler’s layer and Haller’s layer thickness in SSc patients compared to controls. In OCTA analysis, the perfusion of both retinal plexus as well as Sattler’s and Haller’s layer were significantly reduced in the SSc group. Patients with a disease duration of more than 60 months showed a statistically significant positive correlation between retinal and choroidal malperfusion, while those with a shorter disease duration did not.

Conclusion

OCTA analysis confirmed impairment of retinal and choroidal microperfusion in SSc patients, supporting the hypothesis of wide spreading vascular injury. In early stages, either the retinal or the choroidal perfusion seems to be involved, while later on, vascular impairment affects both tissues alike. Both, retinal and choroidal examinations should be considered as soon as the diagnosis of SSc is made, to avoid missing out on early alterations.

Foveal avascular zone segmentation in optical coherence tomography angiography images using a deep learning approach

The purpose of this study was to introduce a new deep learning (DL) model for segmentation of the fovea avascular zone (FAZ) in en face optical coherence tomography angiography (OCTA) and compare the results with those of the device’s built-in software and manual measurements in healthy subjects and diabetic patients. In this retrospective study, FAZ borders were delineated in the inner retinal slab of 3 × 3 enface OCTA images of 131 eyes of 88 diabetic patients and 32 eyes of 18 healthy subjects. To train a deep convolutional neural network (CNN) model, 126 enface OCTA images (104 eyes with diabetic retinopathy and 22 normal eyes) were used as training/validation dataset. Then, the accuracy of the model was evaluated using a dataset consisting of OCTA images of 10 normal eyes and 27 eyes with diabetic retinopathy. The CNN model was based on Detectron2, an open-source modular object detection library. In addition, automated FAZ measurements were conducted using the device’s built-in commercial software, and manual FAZ delineation was performed using ImageJ software. Bland–Altman analysis was used to show 95% limit of agreement (95% LoA) between different methods. The mean dice similarity coefficient of the DL model was 0.94 ± 0.04 in the testing dataset. There was excellent agreement between automated, DL model and manual measurements of FAZ in healthy subjects (95% LoA of − 0.005 to 0.026 mm² between automated and manual measurement and 0.000 to 0.009 mm² between DL and manual FAZ area). In diabetic eyes, the agreement between DL and manual measurements was excellent (95% LoA of − 0.063 to 0.095), however, there was a poor agreement between the automated and manual method (95% LoA of − 0.186 to 0.331). The presence of diabetic macular edema and intraretinal cysts at the fovea were associated with erroneous FAZ measurements by the device’s built-in software. In conclusion, the DL model showed an excellent accuracy in detection of FAZ border in enfaces OCTA images of both diabetic patients and healthy subjects. The DL and manual measurements outperformed the automated measurements of the built-in software.

Evaluating Retinal and Choroidal Perfusion Changes After Ocular Massage of Healthy Eyes Using Optical Coherence Tomography Angiography

Background and objectives: Ocular massage (OM) is used as a treatment option for acute retinal artery occlusion, under the assumption that it induces vessel dilatation and enhances perfusion. Since evidence of ocular perfusion alteration due to OM is lacking, we investigate the impact of OM on the hemodynamics of the posterior pole in healthy eyes in a noninvasive fashion by using optical coherence tomography angiography (OCTA). Materials and Methods: A prospective study was conducted on healthy volunteers, each of whom underwent measurements of intraocular pressure (IOP), central macular thickness (CMT), subfoveal choroidal thickness (SFCT), radial peripapillary capillary perfusion (RPCP), superficial capillary plexus perfusion (SCPP), deep capillary plexus perfusion (DCPP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP) and Haller’s layer perfusion (HLP) before and after OM. OM was performed for 2 min, consisting of 10-s turns of compression and decompression of the globe. Results: A total of 21 eyes from 21 participants (median age 29) were included. After OM, IOP significantly declined (p < 0.001), while SFCT (p < 0.005), SCPP (p < 0.001), DCPP (p = 0.004) and CCP (p = 0.008) significantly increased. CMT, RPCP, SLP and HLP did not show any significant alteration due to OM. Changes in SCPP correlated positively with changes in CCP and vice versa. Conclusions: OCTA-based analysis in healthy adults following OM demonstrated a significant increase of retinal perfusion values, assumed to be due to failure of autoregulatory mechanisms. These findings may indicate a positive effect of OM as a treatment option for patients with acute retinal artery occlusion.

Superficial and Deep Foveal Avascular Zone Area Measurement in Healthy Subjects Using Two Different Spectral Domain Optical Coherence Tomography Angiography Devices

Purpose

To compare the area of the foveal avascular zone (FAZ) in the superficial and deep retinal layers using two different spectral-domain optical coherence tomography angiography (OCTA) devices.

Methods

A cross-sectional comparative study was conducted to obtain macular OCTA images from healthy subjects using Optovue RTVue XR Avanti (Optovue, Inc, Fremont, CA) and Spectralis HRA+OCTA (Heidelberg Engineering, Heidelberg, Germany). Two independent trained graders measured the FAZ area using automated slab segmentation. The FAZ area in the superficial and deep retinal layers were compared.

Results

Twenty-three eyes of 23 subjects were included. The graders agreement was excellent (>0.86) for all measurements. The mean FAZ area was significantly larger at the superficial retinal layer as compared to the deep retinal layer on both devices (0.31 ± 0.08 mm2 vs 0.26 ± 0.08 mm2 in Optovue and 0.55 ± 0.16 mm2 vs 0.36 ± 0.13 mm2 in Spectralis, both P< 0.001). The mean FAZ area was significantly greater in the superficial and deep retinal layers using Spectralis as compared to Optovue measurements (P< 0.001 for both comparisons).

Conclusion

In contrast to previous reports, the FAZ area was larger in the superficial retina as compared to deep retinal layers using updated software versions. Measurements from different devices cannot be used interchangeably.

Stepwise segmentation error correction in optical coherence tomography angiography images of patients with diabetic macular edema

Aim:

To determine the minimum number of optical coherence tomography B-scan corrections required to provide acceptable vessel density measurements on optical coherence tomography angiography images in eyes with diabetic macular edema.

Methods:

In this prospective, noninterventional case series, the optical coherence tomography angiography images of eyes with center-involving diabetic macular edema were assessed. Optical coherence tomography angiography imaging was performed using RTVue Avanti spectral-domain optical coherence tomography system with the AngioVue software (V.2017.1.0.151; Optovue, Fremont, CA, USA). Segmentation error was recorded and manually corrected in the inner retinal layers in the central foveal, 100th and 200th optical coherence tomography B-scans. The segmentation error correction was then continued until all optical coherence tomography B-scans in whole en face image were corrected. At each step, the manual correction of each optical coherence tomography B-scan was propagated to whole image. The vessel density and retinal thickness were recorded at baseline and after each optical coherence tomography B-scan correction.

Results:

A total of 36 eyes of 26 patients were included. To achieve full segmentation error correction in whole en face image, an average of 1.72 ± 1.81 and 5.57 ± 3.87 B-scans was corrected in inner plexiform layer and outer plexiform layer, respectively. The change in the vessel density measurements after complete segmentation error correction was statistically significant after inner plexiform layer correction. However, no statistically significant change in vessel density was found after manual correction of the outer plexiform layer. The vessel density measurements were statistically significantly different after single central foveal B-scan correction of inner plexiform layer compared with the baseline measurements (p = 0.03); however, it remained unchanged after further segmentation corrections of inner plexiform layer.

Conclusion:

Multiple optical coherence tomography B-scans should be manually corrected to address segmentation error in whole images of en face optical coherence tomography angiography in eyes with diabetic macular edema. Correction of central foveal B-scan provides the most significant change in vessel density measurements in eyes with diabetic macular edema.

Association Between Clinical Biomarkers and Optical Coherence Tomography Angiography Parameters in Type 2 Diabetes Mellitus

Purpose

To investigate the clinical significance of the changes in the macular microvasculature in patients with diabetes mellitus type 2 without diabetic retinopathy.

Methods

Fifty-five patients with diabetes mellitus type 2 without diabetic retinopathy and 48 healthy individuals were enrolled in a prospective cross-sectional study. We identified the changes of optical coherence tomography angiography parameters (foveal avascular zone [FAZ] area and circularity, vessel density, and perfusion index) of the 6 × 6-mm macular scan. Correlation and multiple regression analyses were performed between optical coherence tomography angiography parameters and previously known diabetes mellitus type 2-related demographic and systemic characteristics, and serum biochemical markers.

Results

FAZ parameters and perfusion index of the superficial and deep vascular plexus showed significant correlation with serum insulin level, and homeostasis model assessment indices. In multiple linear regression analysis, low insulin levels predicted increased FAZ areas in both the superficial (β = –0.007; P = 0.030) and deep layers (β = –0.010; P = 0.018) and a decreased perfusion index in the deep layer (β = 0.003; P = 0.001).

Conclusions

The expansion and loss of circularity of the FAZ and the decrease in the perfusion index may be affected by insulin resistance and secretory capacity in patients with diabetes mellitus type 2 with no diabetic retinopathy.

Ocular Blood Flow Changes Impact Visual Acuity Gain after Surgical Treatment for Idiopathic Epiretinal Membrane

Background: Idiopathic epiretinal membrane (iERM) is a common eye disease, which can be treated by surgical removal of the fibrotic tissue. Morphological outcome is generally evaluated by optical coherence tomography (OCT). Here, we investigate the impact of surgery on hemodynamics of the posterior pole, using OCT angiography (OCTA). Methods: Patients with unilateral iERM and indication for treatment were included. OCT and OCTA images of the posterior pole were obtained preoperatively and 3-months after 23G vitrectomy with membrane peeling. Parameters of interest included full retinal perfusion, choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP), and Haller’s layer perfusion, which were evaluated longitudinally and also compared to unaffected fellow eyes. Using these parameters, multiple regression analyses were used to predict visual outcomes. Results: Sixty-three iERM eyes were recruited, which initially showed a significant bigger central retinal thickness (p < 0.001) and total macular volume (TMV) (p < 0.001) compared to fellow eyes, while perfusion parameters were alike. Three months later, treated eyes had a statistically significant thicker subfoveal choroid (p = 0.006) and showed an increase of CCP (p = 0.003), while SLP decreased (p = 0.014). Lower preoperative TMV and higher SLP were associated with better postoperative visual outcome. Conclusion: In this OCTA study, iERM itself does not affect the choroidal circulation. However, preoperative choroidal circulation will be a biomarker to know the influence on the choroidal circulation after ERM surgery and may be considered as a predictor for visual outcome.

Evaluating diurnal variations in retinal perfusion using optical coherence tomography angiography

Background

Optical coherence tomography angiography (OCTA) is a non-invasive tool for imaging and quantifying the retinal and choroidal vasculature as well as perfusion state in healthy eyes. Choroidal perfusion is subject to diurnal variation, showing lowest perfusion in the morning and highest in the afternoon. In this index study, OCTA was used to investigate diurnal changes of the retinal perfusion in healthy adult eyes and to identify impacting factors since retinal perfusion is known to be mainly determined by autoregulatory mechanisms.

Methods

A prospective study was conducted on healthy volunteers, each of whom underwent repeated measurements of mean arterial pressure (MAP), intraocular pressure (IOP), macular volume (MV), subfoveal choroidal thickness (SFCT), foveal avascular zone (FAZ) and retinal perfusion of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and full retina (FR) slab at 7 a.m. and 4 p.m. Possible influence of MAP or IOP on the retinal perfusion was evaluated.

Results

A total of 22 eyes of 22 participants (mean age 55.91 ± 14.84) were analysed. Significant diurnal changes from 7 a.m. to 4 p.m. were observed for MAP (p < 0.001) and SFCT (p = 0.017). The perfusion of SCP, DCP and FR as well as the size of the FAZ and the MV did not show significant fluctuation during the day. No significant correlation between MAP or IOP and retinal perfusion values were detectable.

Conclusion

OCTA-based analysis of the retina in healthy adults demonstrated a steady perfusion of both plexus during the day, independently of changes in MAP. These findings support the theory of autoregulatory mechanisms of the retinal blood flow.

Evaluation of retinal microvascular perfusion in hereditary angioedema: a case-control study

Evidence supports that hereditary angioedema (HAE) may be considered as a paroxysmal permeability disorder with defective but self-limiting endothelial barrier dysfunction. A potential subclinical abnormal vascular permeability at retinal capillaries could induce damage resulting in retinopathy. We aimed at exploring for the first time the presence of microangiopathy at retinal level from a highly selective cohort of patients with HAE due to C1 esterase inhibitor protein (C1INH) deficiency (type I). We conducted a pilot, prospective, case-control study including 20 type I HAE patients and 20 age−/sex-matched healthy controls (HC). All participants underwent standard ophthalmological examination including visual fields. Superficial and deep capillary plexi in the retina were analyzed by using new optical coherence tomography angiography (OCT-A). A total of 40 eyes from 20 HAE patients and 20 eyes from HC were evaluated. Perimetric indices of visual field were slightly worse in HAE than in controls. OCT-angiograms documented in HAE patients a lower retinal capillary density in both superficial and deep scans and a higher retinal thickness compared to healthy eyes. Our findings firstly documented subclinical abnormalities in retinal microvascular network in type I HAE patients that might be associated with early subtle functional changes. This preliminary evidence supports the hypothesis of a recurrent endothelial barrier failure at retinal level in HAE patients potentially resulting in chronic damage.

Evaluating diurnal changes in choroidal sublayer perfusion using optical coherence tomography angiography

PURPOSE

To investigate diurnal changes of choroidal sublayer perfusion in normal eyes and to identify influencing factors using optical coherence tomography angiography (OCTA).

METHODS

A prospective study was conducted on healthy volunteers, each of whom underwent repeated measurements of subfoveal choroidal thickness (SFCT) via enhanced depth imaging (EDI) optical coherence tomography (OCT) as well as perfusion of choroidal vascular sublayers using OCTA at 7 a.m., 12 p.m., 4 p.m. and 8 p.m. Possible interactions between diurnal variations and other factors, such as mean arterial pressure (MAP), gender and age, were evaluated.

RESULTS

A total of 22 eyes from 22 participants were analysed. Mean age of participants was 56 years. A significant pattern of diurnal variation was observed for SFCT (p < 0.001) as well as perfusion of Sattler's layer (SLP; p = 0.009) and Haller's layer (HLP; p = 0.003). SFCT demonstrated a linear decrease, being thicker in the morning (348 μm) and thinner in the evening (310 μm). Both, SLP and HLP showed a quadratic relation to time of day, increasing from morning (64% and 76%) to afternoon (66% and 77%), before decreasing again in the evening (64% and 76%). HLP changes were significantly associated with fluctuations of MAP (B = 0.0007; CI 0.0001-0.0014; p = 0.047). No significant differences with regard to gender were detectable. However, older participants (≥60 years) had fewer diurnal changes (p = 0.042).

CONCLUSION

Optical coherence tomography angiography-based analysis of choroidal sublayer perfusion demonstrated significant diurnal variations. Therefore, it is important to account for time of day, when comparing longitudinal OCTA data.

Impact of integrated multiple image averaging on OCT angiography image quality and quantitative parameters

PURPOSE

Multiple image averaging (MIA) is a new approach to improve OCT angiography (OCTA) imaging. The aim of this work was to analyze the impact of MIA on image quality and quantitative OCTA parameters.

METHODS

Twenty eyes from 20 healthy volunteers (55.65 ± 14.8 years) were prospectively enrolled. Imaging was performed using two commercially available OCTA devices (Canon OCT HS-100, Optovue AngioVue) using a uniform imaging protocol. Each participant had two single scans of the macula (3 × 3mm, Canon and Optovue) as well as five continuous single scan imaging procedures (3 × 3mm each) using the Canon device. Three out of five of these images with highest quality were manually chosen and then automatically processed by the Canon device using MIA. The superficial retinal plexus of the single scans and of MIA images was analyzed with regard to the device' own image quality scores (IQS), peak signal-to-noise ratio (PSNR), the size of the foveolar avascular zone (FAZ), and vessel density (VD). Image acquisition times were recorded. Parameters were compared between the devices and the different imaging protocols.

RESULTS

Average acquisition time was significantly higher for the MIA compared with the single measurements (29.09 ± 10.19 seconds (s) (MIA) vs. 5.56 ± 2.17 s (Canon single scan) vs. 20.28 ± 6.81 s (Optovue) (p < 0.001)). IQS showed no significant differences between the devices and between the recording protocols. PSNR was 12.38 ± 0.20 (Canon single scan), 13.01 ± 0.36 (Canon MIA), and 14.34 ± 0.60 (Optovue) (p < 0.001 between the groups). Mean FAZ area in Canon single scans was 0.29 ± 0.06 mm², 0.27 ± 0.07 mm² using MIA, and 0.27 ± 0.08 mm² using the Optovue device. There was no significant difference between mean FAZ measurements before and after averaging (Canon single scan vs. MIA, p = 0.168). VD of the parafoveal area using MIA was significantly lower compared with both single scans (p < 0.001).

CONCLUSIONS

MIA can improve PSNR, but it also reduces imaging speed and significantly affects VD measurements. Therefore, when comparing OCTA data, the use of uniform imaging protocols is required.

[Foveal avascular zone and OCT angiography. An overview of current knowledge]

BACKGROUND

The foveal avascular zone (FAZ) has often been analyzed under different aspects in the last decades, mainly by fluorescence angiography (FA); however, the novel technology of optical coherence tomography angiography (OCTA) enables a non-invasive examination, visualization and quantitative analysis of the FAZ, which has recently led to many new findings, especially in a multidisciplinary manner. This article provides an overview of the investigation of the FAZ using OCTA and the new findings that have been obtained using OCTA in recent years.

METHODS

This article is based on a comprehensive literature review.

RESULTS

In many studies a good reproducibility and repeatability of the FAZ measurements by OCTA could be proven, also by comparing different OCTA devices. In patients with ocular pathologies and systemic diseases, e. g. after retinal vein occlusion or retinal surgery and in patients with diabetes mellitus without diabetic retinopathy, differences to healthy control groups and correlations to visual function could be shown. Moreover, in patients with neurological diseases, such as Alzheimer's dementia, changes of the FAZ could be identified.

CONCLUSION

The OCTA is a non-invasive technology, which enables a reliable visualization and reproducible quantification of the FAZ. The size of the FAZ seems to be altered in different retinal and systemic diseases, which also may correlate with visual function; however, long-term studies evaluating the diagnostic value of these changes in the course of the disease are currently lacking.

Automated OCT angiography image quality assessment using a deep learning algorithm

PURPOSE

To expedite and to standardize the process of image quality assessment in optical coherence tomography angiography (OCTA) using a specialized deep learning algorithm (DLA).

METHODS

Two hundred randomly chosen en-face macular OCTA images of the central 3 × 3 mm² superficial vascular plexus were evaluated retrospectively by an OCTA experienced reader. Images were defined either as sufficient (group 1, n = 100) or insufficient image quality (group 2, n = 100) based on Motion Artifact Score (MAS) and Segmentation Accuracy Score (SAS). Subsequently, a pre-trained multi-layer deep convolutional neural network (DCNN) was trained and validated with 160 of these en-face OCTA scans (group 1: 80; group 2: 80). Training accuracy, validation accuracy, and cross-entropy were computed. The DLA was tested in detecting 40 untrained OCTA images (group 1: 20; group 2: 20). An insufficient image quality probability score (IPS) and a sufficient image quality probability score (SPS) were calculated.

RESULTS

Training accuracy was 97%, validation accuracy 100%, and cross entropy 0.12. A total of 90% (18/20) of the OCTA images with insufficient image quality and 90% (18/20) with sufficient image quality were correctly classified by the DLA. Mean IPS was 0.88 ± 0.21, and mean SPS was 0.84 ± 0.19. Discrimination between both groups was highly significant (p < 0.001). Sensitivity of the DLA was 90.0%, specificity 90.0%, and accuracy 90.0%. Coefficients of variation were 0.96 ± 1.9% (insufficient quality) and 1.14 ± 1.6% (sufficient quality).

CONCLUSIONS

Deep learning (DL) appears to be a potential approach to automatically distinguish between sufficient and insufficient OCTA image quality. DL may contribute to establish image quality standards in this recent imaging modality.

Mapping diurnal variations in choroidal sublayer perfusion in patients with idiopathic epiretinal membrane: an optical coherence tomography angiography study

Background

Optical coherence tomography angiography (OCTA) is a non-invasive tool for imaging and quantifying the choroidal vasculature and perfusion state. In this index study, OCTA was used to investigate diurnal changes in choroidal sublayer perfusion in eyes with idiopathic epiretinal membrane (ERM) and to identify impacting factors.

Methods

A prospective study was conducted on volunteers with symptomatic ERM, each of whom underwent repeated measurements of subfoveal choroidal thickness (SFCT) using enhanced-depth imaging optical coherence tomography and perfusion of choroidal vascular sublayers using OCTA at 7 a.m., 12 p.m., 4 p.m., and 8 p.m. Possible interactions between diurnal variations and other factors, such as gender and age, were evaluated.

Results

A total of 21 eyes of 21 participants (mean age 72.43 ± 7.06 years) were analysed. A significant pattern of diurnal variation was observed for SFCT (p = 0.008) as well as perfusion of Haller's layer (HLP, p = 0.001). SFCT and HLP both demonstrated a quadratic relation to time of the day, decreasing from morning to afternoon, before increasing again in the evening. No significant differences with regard to gender or age were detectable.

Conclusion

OCTA-based analysis of choroidal sublayer perfusion demonstrated significant diurnal variations in patients with symptomatic ERM, which are quite different from changes reported in healthy eyes. Therefore, it is important to account for time of day, when comparing longitudinal OCTA data.

Effect of segmentation error correction on optical coherence tomography angiography measurements in healthy subjects and diabetic macular oedema

Purpose

To evaluate the impact of segmentation error on vessel density measurements in healthy eyes and eyes with diabetic macular oedema (DMO).

Methods

In this prospective, comparative, non-interventional study, enface optical coherence tomography angiography (OCTA) images of the macula from healthy eyes and eyes with DMO were acquired. Two expert graders assessed and corrected the segmentation error. The rate of segmentation error and the changes in vessel density and inner retinal thickness after correction of the segmentation error were recorded and compared between the two groups.

Results

20 eyes with DMO and 24 healthy eyes were evaluated. Intergrader agreement was excellent (intraclass correlation coefficient ≥0.9) for all parameters in both groups. The rate of segmentation error was 33% and 100% in healthy and diabetic eyes, respectively (p<0.001). Nine healthy eyes (37.5%) and all eyes with DMO (100%) were noted to exhibit a change in at least one of the foveal or parafoveal vessel density measurements. The rate of any change in foveal and parafoveal vessel densities in both the superficial and deep capillary plexus was statistically significantly higher in the diabetic group (all p<0.001). No statistically significant change was observed in mean vessel density (superficial and deep capillary plexuses) after correction of the segmentation error in healthy and DMO eyes (All p>0.05). However, the mean absolute change in the vessel density measurements was statistically significantly higher in the diabetic group (all p<0.05). The mean absolute change in superficial and deep inner retinal thickness was statistically significantly higher in DMO (p=0.02 and p=0.002, respectively).

Conclusions

In this study, misidentification of retinal layers and consequent vessel density measurement error occurred in all eyes with DMO and in one-third of healthy eyes. The segmentation error should be checked and manually corrected in the OCTA vessel density measurements, especially in the presence of macular oedema.

Choroidal neovascularization imaging using multiple en face optical coherence tomography angiography image averaging

PURPOSE

To determine the effects of averaging five en face optical coherence tomography angiographic (OCTA) images on the quality of the images in eyes with a choroidal neovascularization (CNV).

METHODS

Twenty-seven eyes of 25 patients (18 men, 7 women; average age 71.0 years) with a CNV were examined by OCTA (OCT HS-100, Canon. Japan). A 3 × 3-mm image including the CNV was recorded and automatically segmented between the retinal outer layers. Analyses were performed on a single image (S-image) and the average of five single images of the same area (A-images). The region of the CNV was selected by ImageJ, and the peak signal-to-noise ratio (PSNR), the vascular density (VD), fractal dimension (FD), and the noise component using band pass filter (BPF) processing of the S- and A-images of each case were compared.

RESULTS

The average PSNR for the A-images was 14.0 which was significantly higher than the 12.2 for the S-images (P < 0.01). However, the average VD was 33.6% for the S-images and 34.8% for the A-images (P > 0.1). The average FD was 1.67 for the S-images and 1.54 for the A-images (P < 0.01). The mean luminance difference obtained by subtracting the luminance of the A-image from the S-image after BPF processing was 10.41 ± 14.66 db which was positive for all eyes.

CONCLUSIONS

The better quality of the A-images of a CNV and absence of a significant difference in the vascular density indicates that the improvement was due to the removal of the same signal levels of the noise component and blood vessels.

Optical coherence tomography angiography image quality assessment at varying retinal expertise levels

Purpose

To compare optical coherence tomography angiography (OCT-A) image quality gradings performed by readers of varying retinal expertise levels in different retinal diseases.

Methods

Central 3 × 3 mm² OCT-A images (AngioVue, Optovue) of 57 healthy controls (50.9 ± 22.4 years) and 148 patients (66.5 ± 14.1 years) affected by various chorioretinal diseases were retrospectively analyzed including early age-related macular degeneration (AMD, n = 26), neovascular AMD (nAMD, n = 22), and geographic atrophy due to AMD (GA, n = 6), glaucoma (n = 28), central serous chorioretinopathy (CSC, n = 14), epiretinal membrane (EM, n = 26), retinitis pigmentosa (RP, n = 16), and retinal venous occlusion (RVO, n = 10). A senior expert in medical retina (SE), an ophthalmology resident (OR), and a non-ophthalmologic medical doctor (MD) independently assessed OCT-A image quality using the motion artifact score (MAS) and the segmentation accuracy score (SAS).

Results

Regarding MAS, inter-reader agreement between SE and OR was 93.7% (Cohen's kappa = 0.907) and 85.4% (Cohen's kappa = 0.786) between SE and MD. Regarding SAS, inter-reader agreement between SE and OR was 95.1% (Cohen's kappa = 0.92) and 92.2% (Cohen's kappa = 0.874) between SE and MD. In the SAS analysis, signal strength index (SSI) and presence of retinal pathology had a significant influence on the overall agreement (P = 0.046; P < 0.001).

Conclusions

OCT-A image quality assessment can be performed most reliably by an ophthalmologist with knowledge in retinal image analysis. Yet, well-instructed non-ophthalmologic assessors show only slightly inferior results and, thus, may be integrated in routine OCT-A image quality assessment as well.

Variability of Foveal Avascular Zone Metrics Derived From Optical Coherence Tomography Angiography Images

Purpose

To characterize sources of inter- and intrasubject variability in quantitative foveal avascular zone (FAZ) metrics.

Methods

Two 3×3-mm optical coherence tomography angiography scans (centered on the fovea) were acquired in both eyes of 175 subjects. An image of the superficial plexus was extracted from each scan and segmented twice by a single observer. Four quantitative FAZ morphology metrics (area, axis ratio, acircularity, major horizontal axis angle) were calculated, and a variance components analysis was performed.

Results

Mean (±SD) age was 27.9 ± 11.9 years, and 55% were female. Area had the largest amount of variance resulting from intersubject differences (93.1%). In contrast, there was large interocular variance for axis ratio, acircularity, and major horizontal axis angle (55.0%, 53.7%, 70.7%, respectively), though only axis ratio showed significant asymmetry between fellow eyes (P < 0.05). Neither repeated images from the same eye nor repeated segmentation on the same image were significant sources of variance.

Conclusions

Metrics of FAZ morphology show excellent repeatability and reliability. Excluding FAZ area, there was a high amount of variance attributed to interocular differences for the other FAZ metrics; therefore, the fellow eye should not be considered a control for FAZ studies when using these metrics.

Translational Relevance

Vision scientists must be prudent when choosing FAZ metrics, as they display varying degrees of within-subject differences relative to between-subject differences. It seems likely that different metrics will be best suited for different tasks, such as monitoring small changes over time within a single subject or assessing whether a given FAZ is abnormal.