The impact of different thresholds on optical coherence tomography angiography images binarization and quantitative metrics

Clinical and Imaging Biomarkers Associated with Outer Retinal Atrophy Onset in Exudative Age-Related Macular Degeneration: A Real-Word Prospective Study

INTRODUCTION

Macular neovascularization (MNV) secondary to age-related macular degeneration (AMD) is well managed by anti-vascular endothelial growth factor (anti-VEGF) intravitreal injections. However, outer retinal atrophy represents an unavoidable occurrence detected during follow-up. Several imaging metrics have been proposed as clinically relevant in stratifying the risk of onset of outer retinal atrophy. The main goal of this study is to evaluate the impact of noninvasive imaging metrics on the assessment of outer retinal atrophy onset in a large cohort of eyes with neovascular AMD managed in a real-world setting.

METHODS

This study was a prospective, observational, case series. We included patients affected by newly diagnosed neovascular AMD, requiring anti-VEGF intravitreal injections. We collected clinical and imaging data, with a planned follow-up of 24 months. The multimodal imaging protocol included optical coherence tomography, optical coherence tomography angiography, and fundus autofluorescence. We collected noninvasive imaging metrics and we assessed the relationship with the morphological and functional outcome evaluated at 12-month and 24-month time points.

RESULTS

We included 370 eyes of 370 patients with exudative AMD (210 male; mean age 79 ± 8 years). MNV were classified as follows: type 1, 198 (54%); type 2, 89 (24%); polypoidal choroidal vasculopathy, 29 (7%); and type 3, 54 (15%). A total of 120 out of 370 eyes (33%) showed complete outer retinal atrophy at the end of the 2-year follow-up. The presence of intraretinal fluid, thinning of the Sattler choroidal layer, late anti-VEGF switch, the overall number of anti-VEGF injections, and the perfusion characteristics of the MNV were found to be the most relevant factors associated with the onset of outer retinal atrophy. The other collected metrics were found to be less clinically relevant, also showing no cumulative effect in the multivariate analysis (p > 0.05).

CONCLUSIONS

We identified imaging metrics significantly associated with the 2-year risk onset of outer retinal atrophy. These metrics might pave the way for the development of future customized anti-VEGF treatment strategies.

Computational Retinal Microvascular Biomarkers from an OCTA Image in Clinical Investigation

Retinal structural and functional changes in humans can be manifestations of different physiological or pathological conditions. Retinal imaging is the only way to directly inspect blood vessels and their pathological changes throughout the whole body non-invasively. Various quantitative analysis metrics have been used to measure the abnormalities of retinal microvasculature in the context of different retinal, cerebral and systemic disorders. Recently developed optical coherence tomography angiography (OCTA) is a non-invasive imaging tool that allows high-resolution three-dimensional mapping of the retinal microvasculature. The identification of retinal biomarkers from OCTA images could facilitate clinical investigation in various scenarios. We provide a framework for extracting computational retinal microvasculature biomarkers (CRMBs) from OCTA images through a knowledge-driven computerized automatic analytical system. Our method allows for improved identification of the foveal avascular zone (FAZ) and introduces a novel definition of vessel dispersion in the macular region. Furthermore, retinal large vessels and capillaries of the superficial and deep plexus can be differentiated, correlating with retinal pathology. The diagnostic value of OCTA CRMBs was demonstrated by a cross-sectional study with 30 healthy subjects and 43 retinal vein occlusion (RVO) patients, which identified strong correlations between OCTA CRMBs and retinal function in RVO patients. These OCTA CRMBs generated through this "all-in-one" pipeline may provide clinicians with insights about disease severity, treatment response and prognosis, aiding in the management and early detection of various disorders.

MICROVASCULATURE ALTERATIONS OF PERIPAPILLARY RETINA AND MACULA IN SYSTEMIC LUPUS ERYTHEMATOSUS PATIENTS WITHOUT OCULAR INVOLVEMENT BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To evaluate microvasculature alterations of the peripapillary retina and macula and to assess whether the changes can detect preclinical retinopathy in systemic lupus erythematosus patients.

METHODS

Cross-sectional study of 32 systemic lupus erythematosus patients without retinopathy and 22 normal controls. Optical coherence tomography angiography was used to measure the microvasculature of the peripapillary retina and macula. Vessel densities (VD, %) and fractal dimensions of superficial capillary plexus (SCP) and deep capillary plexus were calculated.

RESULTS

Compared with controls, macular vessel densities of the whole image SCP (macular vessel density of SCP-wi) and macular vessel density of inferior SCP (macular vessel density of SCP-i) were significantly reduced in systemic lupus erythematosus patients ( P < 0.05). The peripapillary vessel densities (peripapillary vessel density [pVD]) of a 2.5-mm circle of SCP (pVD of SCP Φ2.5 ), pVD of SCP Φ3.5 , and pVD of inferior region of the inner circle of SCP (pVD of SCP-ii) were significantly reduced in patients treated with hydroxychloroquine >5 years. Macular vessel density of SCP-wi declined with age (β = -0.12; P < 0.01) and pVD of SCP-ii declined with hydroxychloroquine cumulative dose (β = -0.01; P < 0.01). Macular vessel density of SCP-i had the best discrimination power of 0.77 ( P < 0.01).

CONCLUSION

Systemic lupus erythematosus patients without ocular involvement had microvasculature alterations that were particularly evident in the SCP. Peripapillary retina microvasculature may be reduced in patients with longer hydroxychloroquine treatment.

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.

Influence of binarization methods on the fractal dimension of alveolar bone using digital radiographs

OBJECTIVE

The aim of this study was to evaluate the influence of binarization methods (BnMs) on the fractal dimension (FD) of the alveolar bone in digital radiographic images.

STUDY DESIGN

Five identical periapical radiographs were obtained from each of 20 anatomic regions. Using ImageJ/Fiji software, a standardized region of interest was positioned in the trabecular bone of all radiographs, 14 BnMs were independently applied, and FD was calculated. The Friedman test and Dunn post hoc tests were used to evaluate the influence of BnMs on FD (α = 0.05). The intraclass correlation coefficient (ICC) was used to assess correlation among BnMs.

RESULTS

No significant differences were observed in the threshold value between the BnMs. No significant differences in FD were observed among 9 BnMs (Default, Huang, Iso Data, Li, Mean, Min Error[I], Moments, Otsu, and Shanbhag). These methods presented significantly higher FDs than those from 3 other BnMs (Max Entropy, Renyi Entropy, and Yen), which did not significantly differ from each other. The Triangle method significantly differed from all BnMs, and the Percentile method produced significantly higher FDs than Huang, IsoData, Li, Moments, Otsu, and Shanbhag. Most BnMs presented good or excellent correlation (ICC ≥ 0.76).

CONCLUSIONS

Binarization methods influence FD of the alveolar bone from digital periapical radiographs; thus, this technical aspect is relevant for comparison purposes and should be standardized. For comparison of published FD research, the Default method is recommended.

Qualitative and quantitative comparison of two semi-manual retinal vascular density analyzing methods on optical coherence tomography angiography images of healthy individuals

The aim of this study was to evaluate qualitative and quantitative differences in vascular density analysis of an established and a novel alternative for post-processing on optical coherence tomography angiography (OCTA) images in healthy individuals. OCTA examinations of 38 subjects were performed. After extracting the images, two semi-manual post-processing techniques, the already established Mexican hat filtering (MHF) and an alternative, the Shanbhag thresholding (ST) were applied. We assessed Vessel Density (VD), Skeleton Density (SkD) and Vessel Diameter Index (VDI). We analyzed the results in order to establish similarities or potentially relevant differences. Regarding SkD and VD, MHF generally gave higher values than ST. Simultaneously, mean values were also predominantly higher by MHF; however, standard deviations (SD) were higher by ST (range [mean ± SD]: 0.054 ± 0.038 to 0.134 ± 0.01 and 0.134 ± 0.095 to 0.362 ± 0.028 vs 0.012 ± 0.014 to 0.087 ± 0.03 and 0.039 ± 0.047 to 0.4 ± 0.095 for SkD and VD with MHF vs SkD and VD with ST, respectively). Values of VDI were considerably higher with ST than with MHF, while standard deviation was still significantly higher with ST (range [mean ± SD]: 2.459 ± 0.144 to 2.71 ± 0.084 and 2.983 ± 0.929 to 5.19 ± 1.064 for VDI with MHF and ST, respectively). The noise level reduction of the two methods were almost identical (noise levels: 65.8% with MHT and 65.24% with ST). Using MHF, the vascular network gets more fragmented by an average of 40% compared to ST. Both methods allow the segmentation of the vascular network and the examination of vascular density parameters, but they produce largely inconsistent results. To determine if these inconsistent results are clinically meaningful, and which method is more suitable for clinical use, our results provide further evidence that detailed understanding of the image analysis method is essential for reliable decision making for patients with retinal pathology. For longitudinal monitoring, use of the same image processing method is recommended.

ABNORMALITIES IN THE RETINAL CAPILLARY PLEXUSES IN COATS DISEASE IN ADULTHOOD ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To describe and quantify the abnormalities of the retinal capillary plexuses using optical coherence tomography angiography in Coats disease.

METHODS

Retrospective study. Eleven eyes of 11 patients with Coats disease (9 men and two women aged 32-80 years) compared with nine fellow eyes and 11 healthy control eyes. Horizontal bands of contiguous 3 × 3 mm optical coherence tomography angiograms of the superficial vascular plexus and deep capillary complex were acquired from the optic disk to 6 mm temporal to the fovea, through areas with telangiectasia visible on fluorescein angiography in 9 cases.

RESULTS

The vascular density was significantly decreased in both plexuses in eyes with Coats disease compared with normal and fellow eyes within the 6 mm temporal to the fovea (superficial vascular plexus: 21.5 vs. 29.4%, P = 0.00004 and vs. 30.3%, P = 0.00008; deep capillary complex, 16.5 vs. 23.9%, P = 0.00004 and vs. 24.7%, P = 0.00008, respectively). The fractal dimension was also significantly decreased in eyes with Coats disease (superficial vascular plexus: 1.796 vs. 1.848 P = 0.001 and vs. 1.833, P = 0.003; deep capillary complex: 1.762 vs. 1.853, P = 0.003 and vs. 1.838, P = 0.004, respectively).

CONCLUSION

Retinal plexuses' vascular density was decreased in Coats disease, including in areas with no visible telangiectasia.

Perivenular Capillary Rarefaction in Diabetic Retinopathy: Interdevice Characterization and Association to Clinical Staging

Purpose

Geometric perfusion deficit (GPD) is a newly described OCT angiography (OCTA) parameter identifying the total area of presumed retinal ischemia. The aim of our study is to characterize differences in GPD and other common quantitative OCTA parameters between macular full field, perivenular zones, and periarteriolar zones for each clinical stage of nonproliferative diabetic retinopathy (DR) and to assess the influence of ultrahigh-speed acquisition and averaging on the described differences.

Design

Prospective observational study.

Participants

Forty-nine patients, including 11 (22.4%) with no sign of DR, 12 (24.5%) with mild DR, 13 (26.5%) with moderate DR, and 13 (26.5%) with severe DR. Patients with diabetic macular edema, proliferative DR, media opacity, head tremor, and overlapping retinal diseases or systemic diseases influencing OCTA were excluded.

Methods

OCT angiography was performed 3 times for each patient: 1 using Solix Fullrange single volume (V1) mode, 1 using Solix Fullrange 4 volumes mode with automatically averaged scan (V4), and 1 using AngioVue.

Main Outcome Measures

Full macular, periarteriolar, and perivenular perfusion density (PD), vessel length density (VLD), vessel density index, and GPD for both the superficial capillary plexus (SCP) and deep capillary plexus (DCP).

Results

In patients showing no sign of DR, PD and VLD were significantly lower in the perivenular area in both the DCP and SCP using V1 and V4, whereas GPD was significantly higher in the perivenular zone in the DCP and SCP with all 3 devices. In patients with mild DR, all 3 measurements (PD, VLD, and GPD) were significantly different in the perivenular zone with all 3 devices. In patients with moderate DR, PD and VLD were lower in the DCP and SCP when measured with V1 and V4. Moreover, GPD was higher in the perivenular zone in the DCP with all 3 devices, whereas only V4 detected a difference in the SCP. In severe DR, only V4 detected a lower PD and VLD and a higher GPD in the DCP of the perivenular zone. V4 also detected a higher GPD in the SCP.

Conclusions

Geometric perfusion deficit highlights prevalent perivenular location of macular capillary ischemia in all stages of DR. In severe DR patients, only averaging technology allows detection of the same finding.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Morphological and functional involvement of the inner retina in retinitis pigmentosa

BACKGROUND

To investigate the morphological retinal parameters associated with retinal sensitivity status in retinitis pigmentosa (RP) through a quantitative multimodal imaging approach.

METHODS

The study was designed as an observational, prospective case series, including RP patients and healthy controls. Multimodal imaging included fundus autofluorescence (FAF), structural optical coherence tomography (OCT), OCT angiography (OCTA) and microperimetry (MP). The follow-up lasted 12 months. For each imaging modality, we performed an overall quantitative analysis and a detailed investigation based on the ETDRS-9 sectors grid. Quantitative parameters included the thickness of each retinal and choroidal layer, vessel density (VD), choriocapillaris porosity (CCP), FAF intensity and MP retinal sensitivity.

RESULTS

We included 40 eyes (40 patients) affected by RP and 40 healthy eyes (40 controls). Mean baseline BCVA was 0.14 ± 0.18 LogMAR, with 0.18 ± 0.24 LogMAR after 1-year of follow-up. RP eyes showed statistically significant alterations of retinal and choroidal layers on the ETDRS-9 sectors grid, significant reduction of VD values and MP retinal sensitivity, and significantly higher CCP than controls. The inner retinal layers proved closely associated with the functional integrity of the posterior pole. In addition, our ROC analysis provided quantitative cutoffs connected significantly with a high probability of observing a partial sparing of MP retinal sensitivity.

CONCLUSIONS

The inner retinal layers are closely associated with the functional integrity of the posterior pole in RP. FAF intensity reduction may be interpreted as lipofuscin metabolism impairment inducing increased phototoxic distress for retinal structures. Vascular involvement contributes to the morpho-functional deterioration of the macular region in RP.

Confocal MultiColor Signal Depends on Perfusion Characteristics of Retinal Microaneurysms in Diabetic Retinopathy as Detected by OCTA

Purpose

To propose a noninvasive way of classifying multimodal imaging of retinal microaneurysms (MA) secondary to diabetic retinopathy (DR).

Methods

The research was designed as a cross-sectional, observational study of patients affected by DR. Multimodal imaging included confocal MultiColor imaging, optical coherence tomography (OCT) and OCT angiography (OCTA). MA green- and infrared-reflectance components were assessed by confocal MultiColor imaging, reflectivity properties by OCT, and MA perfusion features by OCTA. In addition, we included high-resolution (HR) and high-speed (HS) OCTA scans to assess HR-HS agreement in detecting retinal MA and to highlight different perfusion features detected by both OCTA acquisitions.

Results

We analyzed 216 retinal MAs, divided into green (46; 21%), red (58; 27%) and mixed types (112; 52%). Green MAs were mainly hyper-reflective on OCT, with no or poor filling on OCTA. Red MAs were characterized by an isoreflective signal on OCT and full filling on OCTA. Mixed MAs showed a hyper-reflective border and a hyporeflective core on OCT and partial filling on OCTA. No differences in red MA HR/HS size discrepancy and reflectivity were found, whereas these progressively increased as the MA MultiColor signal changed from infrared to green. MA types significantly correlated with visual acuity, DR duration, and DR severity.

Conclusions

Retinal MA can be classified reliably by means of a fully noninvasive multimodal imaging-based assessment. MA types are matched with visual acuity, DR duration and DR severity. Both HR and HS OCTA are highly effective in detecting MA, although HR OCTA is to be preferred in the presence of fibrotic evolution.

Translational Relevance

This study outlines a proposed novel MA classification based on noninvasive multimodal imaging. The findings presented in this paper endorse the clinical relevance of this approach, highlighting how this classification is associated with both DR duration and severity.

Comparison of Automated Thresholding Algorithms in Optical Coherence Tomography Angiography Image Analysis

(1) Background: Calculation of vessel density in optical coherence tomography angiography (OCTA) images with thresholding algorithms varies in clinical routine. The ability to discriminate healthy from diseased eyes based on perfusion of the posterior pole is critical and may depend on the algorithm applied. This study assessed comparability, reliability, and ability in the discrimination of commonly used automated thresholding algorithms. (2) Methods: Vessel density in full retina and choriocapillaris slabs were calculated with five previously published automated thresholding algorithms (Default, Huang, ISODATA, Mean, and Otsu) for healthy and diseased eyes. The algorithms were investigated with LD-F2-analysis for intra-algorithm reliability, agreement, and the ability to discriminate between physiological and pathological conditions. (3) Results: LD-F2-analyses revealed significant differences in estimated vessel densities for the algorithms (p < 0.001). For full retina and choriocapillaris slabs, intra-algorithm values range from excellent to poor, depending on the applied algorithm; the inter-algorithm agreement was low. Discrimination was good for the full retina slabs, but poor when applied to the choriocapillaris slabs. The Mean algorithm demonstrated an overall good performance. (4) Conclusions: Automated threshold algorithms are not interchangeable. The ability for discrimination depends on the analyzed layer. Concerning the full retina slab, all of the five evaluated automated algorithms had an overall good ability for discrimination. When analyzing the choriocapillaris, it might be useful to consider another algorithm.

New Findings in Early-Stage Keratoconus: Lamina Cribrosa Curvature, Retinal Nerve Fiber Layer Thickness, and Vascular Perfusion

PURPOSE

Our aim was to investigate the involvement of posterior pole structures in eyes affected by keratoconus (KC). Optical coherence tomography (OCT) and OCT angiography (OCTA) were used to determine the status of lamina cribrosa (LC), peripapillary retinal nerve fiber layer (RNFL), macular and peripapillary microvasculature.

DESIGN

Observational, cross-sectional, case-control analysis.

METHODS

Single-center investigation involving patients with KC and healthy control subjects. Enrolled subjects underwent anterior segment OCT combined with Placido-disk topography, macular and optic nerve head swept-source OCT and swept-source OCTA scans, and 3D wide glaucoma module for peripapillary RNFL thickness measurement. The LC curvature index was used to express the degree of LC posterior bowing. We calculated the vessel density and vessel length density at the macular superficial capillary plexus, deep capillary plexus, choriocapillaris, and nerve radial peripapillary capillary plexus.

RESULTS

Overall, 32 eyes with KC and an equal number of age- and axial length-matched control eyes were included in the analysis. Almost all (97%) of eyes with KC were classified as early stage. KC displayed a reduction in peripapillary RNFL thickness (104.8 ± 11.9 µm vs 110.7 ± 10.5 µm; P = .039) and nerve radial peripapillary capillary plexus vessel density (46.31% ± 3% vs 43.82% ± 4%; P = .006) when compared with control subjects; these differences were more evident in the temporal sector and were associated with a higher LC curvature index (9.9% ± 2.6% vs 8.48% ± 1.7%; P = .012). Mean macular superficial capillary plexus vessel density was 3 percentage points lower in eyes with KC than in healthy controls (P < .001).

CONCLUSION

Early-stage KC may be characterized by a posterior bowing of the LC along with a subtle peripapillary RNFL thinning and vascular impairment. These findings support the hypothesis that KC may be a corneal manifestation of a more generalized "eye collagen disease."

Characterizing macular edema in retinitis pigmentosa through a combined structural and microvascular optical coherence tomography investigation

The aim of the study was to characterize macular edema (ME) in retinitis pigmentosa (RP) by means of quantitative optical coherence tomography (OCT)-based imaging. The study was designed as observational, prospective case series, with 1-year follow-up. All RP patients underwent complete ophthalmologic assessment, including structural OCT, OCT angiography, and microperimetry (MP). The primary outcome was the characterization through quantitative OCT-based imaging of RP eyes complicated by ME. A total of 68 RP patients' eyes (68 patients) and 68 eyes of 68 healthy controls were recruited. Mean BCVA was 0.14 ± 0.17 LogMAR at baseline and 0.18 ± 0.23 LogMAR at 1-year follow-up (p > 0.05). Thirty-four eyes (17 patients; 25%) showed ME, with a mean ME duration of 8 ± 2 months. Most of the eyes were characterized by recurrent ME. The ME was mainly localized in the inner nuclear layer in all eyes. LogMAR BCVA was similar in all RP eyes, whether with or without ME, although those with ME were associated with higher vessel density values, as well as thicker choroidal layers, than those without ME. In conclusion, the inner retina is closely involved in the pathogenesis of ME. The impairment of retinal-choroidal exchanges and Müller cell disruption might be a major pathogenic factor leading to the onset of ME in RP.

Quantitative approaches in multimodal fundus imaging: State of the art and future perspectives

When it first appeared, multimodal fundus imaging revolutionized the diagnostic workup and provided extremely useful new insights into the pathogenesis of fundus diseases. The recent addition of quantitative approaches has further expanded the amount of information that can be obtained. In spite of the growing interest in advanced quantitative metrics, the scientific community has not reached a stable consensus on repeatable, standardized quantitative techniques to process and analyze the images. Furthermore, imaging artifacts may considerably affect the processing and interpretation of quantitative data, potentially affecting their reliability. The aim of this survey is to provide a comprehensive summary of the main multimodal imaging techniques, covering their limitations as well as their strengths. We also offer a thorough analysis of current quantitative imaging metrics, looking into their technical features, limitations, and interpretation. In addition, we describe the main imaging artifacts and their potential impact on imaging quality and reliability. The prospect of increasing reliance on artificial intelligence-based analyses suggests there is a need to develop more sophisticated quantitative metrics and to improve imaging technologies, incorporating clear, standardized, post-processing procedures. These measures are becoming urgent if these analyses are to cross the threshold from a research context to real-life clinical practice.

Clinical Correlation Between Optical Coherence Tomography Biomarkers and Retinal Sensitivity in Best Vitelliform Macular Dystrophy

Purpose

To investigate the clinical and imaging features associated with retinal sensitivity in Best vitelliform macular dystrophy (BVMD).

Methods

This was a cross-sectional, single-center, observational study. Each patient underwent optical coherence tomography (OCT), near-infrared fundus autofluorescence, and OCT angiography. Macular integrity assessment microperimetry under mesopic conditions was performed to obtain retinal sensitivity thresholds from 68 testing points in the central macula. Structural OCT was used to classify BVMD lesions into four types according to their composition: vitelliform, mixed, subretinal fluid, and atrophy. Multilevel, mixed-effects linear regression was used to determine the factors associated with retinal sensitivity.

Results

The study included 57 eyes of 30 patients with BVMD, 48 of which (84%) were in a clinical stage. Mean retinal sensitivity varied according to the composition of the lesion: the vitelliform type registering the highest (22 ± 4.1 dB), followed by mixed (18.73 ± 2.7 dB), subretinal fluid (15.68 ± 4.2 dB), and atrophy types (11.85 ± 4.6 dB). The factors most strongly associated with mean retinal sensitivity in BVMD proved to be the OCT lesion type and outer nuclear layer thickness.

Conclusions

Retinal sensitivity in BVMD is influenced by lesion composition and outer nuclear layer thickness. Further studies with long-term follow-up are warranted to examine retinal sensitivity over time and to validate retinal sensitivity changes as biomarkers for BVMD.

Translational Relevance

Assessing retinal sensitivity in BVMD provides a new instrument in the clinical characterization of the disease and offers the opportunity to identify imaging biomarkers for use as outcome measures in future clinical trials.

Optical coherence tomography angiography for quantitative microvascular assessment in diabetic retinopathy: inter-device and intra-device agreement and correlation with clinical staging

AIM

To compare acquisitions from single-volume Solix protocol (V1), multi-volume averaged Solix protocol (V4), and AngioVue in patients with diabetic retinopathy (DR) to assess differences in quantitative parameters introduced by high-speed scanning and averaging.

METHODS

Thirty-eight diabetic patients were divided into 4 groups showing either no sign, mild, moderate, or severe DR at fundus examination. For optical coherence tomography angiography (OCTA) acquisitions both AngioVue, Solix V1, and V4 were used on each patient. Outcome measures were macular perfusion density (PD), vessel length density (VLD), and vessel density index (VDI) for both superficial capillary plexus (SCP) and deep capillary plexus (DCP) and flow deficits (FD) in the choriocapillaris (CC).

RESULTS

Our study revealed a good agreement in SCP parameters measured with all 3 devices. DCP measurements with Solix V1 showed moderate agreement with V4 and poor agreement with AngioVue measurements. Inter-device agreement in CC-FD assessment was relatively poor considering all 3 devices. The averaging process led to an underestimation of DCP and SCP parameters in all stages of DR (more evident in mild DR). AngioVue measurements compared to Solix V1 led to overestimation of SCP-PD (more pronounced in severe DR patients) and of DCP parameters (more evidently in moderate DR). The regression model derived from Solix V1 parameters was the best for categorization into the different stages.

CONCLUSIONS

Averaging and high-speed scanning introduce changes in OCTA quantitative parameters in DR. Solix V1 is the most suitable for early diagnosis of DR, while averaged protocol could be the preferred choice in advanced stages of the disease.

Flow and geometrical alterations in retinal microvasculature correlated with the occurrence of diabetic retinopathy: evidence from a longitudinal study

PURPOSE

To assess the relationship between flow and geometric parameters in optical coherence tomography angiography (OCTA) images and the risk of incident diabetic retinopathy (DR).

METHODS

This prospective, observational cohort study recruited patients with type 2 diabetes without DR in Guangzhou, China and followed up annually. A commercially available OCTA device (DRI-OCT Triton; Topcon Inc., Tokyo, Japan) was used to obtain a variety of flow (foveal avascular zone [FAZ] area, vessel density [VD], vessel length density [VLD]) and geometric (fractal dimension [FD] and blood vessel tortuosity [BVT]) parameters in superficial capillary plexus (SCP) and deep capillary plexus (DCP). The odds ratio [OR] and its 95% confidential interval [CI] were calculated per 1-SD increase in each OCTA parameter.

RESULTS

Over a follow-up of one year, 182 of 1,698 participants (10.7%) developed incident DR. After adjusting for conventional risk factors and image quality score, the higher risk of DR onset was significantly associated with the reduced parafoveal VD of SCP (OR=0.81; 95% CI: 0.69, 0.96; P = 0.016), reduced parafoveal VLD of SCP (OR=0.73; 95% CI: 0.59, 0.90; P = 0.003), reduced FD of SCP (OR=0.73; 95% CI: 0.61, 0.87; P < 0.001), increased BVT of SCP (OR=1.39; 95% CI: 1.18, 1.64; P < 0.001) and increased BVT of DCP (OR=1.19; 95% CI: 1.01, 1.40; P = 0.033) .

CONCLUSION

Reduced vessel density and impaired vessel geometry posed higher susceptibility for DR onset in patients with type 2 diabetes, supporting the adoption of OCTA parameters as early monitoring indicators of the newly incident DR.