Macular Vessel Density in Diabetic Retinopathy Patients: How Can We Accurately Measure and What Can It Tell Us?

OCTA-based research on changes of retinal microcirculation in digestive tract malignancy

PURPOSE

This cross-sectional study measured retinal vessel density (VD) in patients with digestive tract malignancy by optical coherence tomography angiography (OCTA), and compared them with healthy controls to explore the retinal microcirculation changes in patients with digestive tract malignancy.

METHODS

106 eligible participants were divided into three groups: gastric cancer (GC) group (36 individuals), colorectal cancer (CRC) group (34 individuals), and healthy control group (36 individuals). Angio 6*6 512*512 R4 and ONH Angio 6*6 512*512 R4 modes were performed to collect retinal vessel density data centered on fovea and papillary, respectively. The retina was automatically segmented into different layers (superficial vascular plexus (SVP), the inner retinal layer, radial peripapillary capillary plexus (RPCP), deep vascular plexus (DVP)) and areas to analyze.

RESULTS

At the optic nerve head (ONH) region, the VD of the inner retinal layer increased in both GC and CRC groups in all quadrants and areas. In the papillary area, VD in the inner retinal layer, SVP, and RPCP increased in the GC and CRC groups. In the parapapillary area, VD in the inner retinal layer increased in the GC and the CRC groups. Significant increase in the global VD were found in the GC group of the RPCP and SVP. Regarding the macular region, no statistical differences were observed in each layer.

CONCLUSIONS

The study suggested that retinal vessel density changed in patients with digestive tract malignancy, especially in the inner retinal layer of the ONH region, revealing the potential relevance of the relation between gastrointestinal cancer and retinal microcirculation.

Evaluation of agreement in macular vascular density measured by different protocols: 4.5 mm × 4.5 mm and 6 mm × 6 mm

PURPOSE

To evaluate the agreement in the macular vascular density (MVD) measured by two protocols: 4.5 mm × 4.5 mm and 6 mm × 6 mm.

DESIGN

Cross-sectional observational study.

METHODS

Healthy volunteers between the age group of 19 and 39 years were recruited. Topcon DRI OCT Triton plus (Topcon Corporation, Tokyo, Japan) was used to acquire the fovea-centered optical coherence tomography angiography (OCTA) image using two protocols: 4.5 mm × 4.5 mm and 6 mm × 6 mm. MVD was measured by the manufacturer software in the superficial capillary plexus slab in five regions: central, superior, nasal, inferior, and temporal subfields of early treatment diabetic retinopathy study grid in each protocol.

RESULTS

The study included 79 eyes of 40 healthy volunteers. The difference in the mean MVD between two protocols was 3.84% in right eye and 4.2% in left eye in central subfield, 0.93% in right eye and 1.13% in left eye in superior subfield, 0.06% in right eye and 1.45% in left eye in nasal subfield, 1.65% in right eye and 0.7% in left eye in inferior subfield, 0.4% in right eye and 0.54% in left eye in temporal subfield. The measurements were significantly higher in 6 mm × 6 mm in central subfield in both the eyes and in nasal field in the left eye. Whereas, the measurements were significantly higher in 4.5 mm × 4.5 mm in superior and inferior subfield in both the eyes and in temporal subfield in the left eye.

CONCLUSION

The protocols should not be used interchangeably and it is necessary to include recommendation of the field of view to measure MVD while standardizing OCTA reporting.

Assessment of early macular microangiopathy in subjects with prediabetes using optical coherence tomography angiography and fundus photography

AIMS

Early detection of retinal microangiopathy in patients with prediabetes may reduce diabetic retinopathy complications. The aim of this study was to assess early macular vascular changes in prediabetics before development of over diabetes using OCTA and fundus photography.

METHODS

In this cross-sectional study, 66 prediabetic individuals and 66 normal controls underwent clinical, laboratory, and fundus photography evaluation followed by OCTA macular imaging to examine for the foveal avascular zone, and area of capillary non-perfusion, thickness, disorganization of vessels, and vessel density perfusion percentage of superficial capillary plexus and deep capillary plexus.

RESULTS

Retinal microangiopathy was detected in 36.4% of prediabetics by OCTA and only in 10.6% by fundus photography. None of clinical or laboratory parameters had significant association with DR. Area of capillary non-perfusion and disorganization of SCP were detected in 53.8% and 56.8%, respectively, in prediabetics. VDP of SCP and DCP of whole image, parafoveal, and perifoveal areas was significantly lower in prediabetes group compared to normal control. VDP of DCP of perifoveal area (β coefficient: - 0.10, OR: 0.91, 95% CI: 0.86-0.96, P < 0.001) and disorganization of DCP (β coefficient: 1.93, OR: 6.89, 95% CI: 2.5-18.8, P < 0.001) were significant predictors of DR in prediabetics. There was no difference in FAZ in prediabetics with and without retinopathy.

CONCLUSIONS

OCTA could detect early retinal vascular changes during the prediabetic state before developing diabetes. VDP was significantly reduced in prediabetic patients. Furthermore, VDP of DCP of perifoveal area and disorganization of DCP were the most important predictors of retinopathy in prediabetic patients.

[Terminology of quantitative optical coherence tomography angiography metrics]

This review is devoted to the English- and Russian-language terminology of quantitative metrics that are used in the evaluation of images obtained by optical coherence tomography angiography (OCT-A). The paper presents an analysis of the use of terms characterizing intraretinal blood flow (vascular density, perfusion density, skeletonized density, etc.), area and shape of the foveal avascular zone, and choriocapillaris blood flow. The factors causing the heterogeneity of OCT-A terminology are described, including the lack of a unified international nomenclature for OCT-A, features of their Russian translation, inconsistency of the parameters in optical coherence tomography systems of different manufacturers. The article also considers ways to standardize the terminology.

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.

Innovative Macula Capillaries Plexuses Visualization with OCTA B-Scan Graph Representation: Transforming OCTA B-Scan into OCTA Graph Representation

Purpose

The aim of this study is to transform optical coherence tomography angiography (OCTA) scans into innovative OCTA graphs, serving as novel biomarkers representing the macular vasculature.

Patients and Methods

The study included 90 healthy subjects and 39 subjects with various abnormalities (29 with diabetic retinopathy, 5 with age-related macular degeneration, and 5 with choroid neovascularization). OCTA 5µm macular coronal views (MCVs) were generated for each subject, followed by blood vessel segmentation and skeleton processing. Subsequently, the blood vessel density index, blood vessel skeleton index, and blood vessel tortuosity index were computed. The graphs of each metric were plotted against the axial axes of the OCTA B-scan, representing the integrity of vasculature at successive 5µm macular depths.

Results

The results revealed two significant findings. First, the B-scans from OCTA can be transformed into OCTA graphs, yielding three specific OCTA graphs in this study. These graphs provide new biomarkers for assessing the integrity of deep vascular complex (DVC) and superficial vascular complex (SVC) within the macula. Second, a statistically significant difference was observed between normal (n=90) and abnormal (n=39) subjects, with a t-test p-value significantly lower than 0.001. The Mann-Whitney u-test also yielded significant difference but only between the 90 normal and 29 DR subjects.

Conclusion

The novel OCTA graphs offer a unique representation of the macula's SVC and DVC, suggesting their potential in aiding physicians in the diagnosis of eye health within OCTA clinics. Further research is warranted to finalize the shape of these newly derived OCTA graphs and establish their clinical relevance and utility.

Optical coherence tomography angiography in diabetic retinopathy

There remain many unanswered questions on how to assess and treat the pathology and complications that arise from diabetic retinopathy (DR). Optical coherence tomography angiography (OCTA) is a novel and non-invasive three-dimensional imaging method that can visualize capillaries in all retinal layers. Numerous studies have confirmed that OCTA can identify early evidence of microvascular changes and provide quantitative assessment of the extent of diseases such as DR and its complications. A number of informative OCTA metrics could be used to assess DR in clinical trials, including measurements of the foveal avascular zone (FAZ; area, acircularity, 3D para-FAZ vessel density), vessel density, extrafoveal avascular zones, and neovascularization. Assessing patients with DR using a full-retinal slab OCTA image can limit segmentation errors and confounding factors such as those related to center-involved diabetic macular edema. Given emerging data suggesting the importance of the peripheral retinal vasculature in assessing and predicting DR progression, wide-field OCTA imaging should also be used. Finally, the use of automated methods and algorithms for OCTA image analysis, such as those that can distinguish between areas of true and false signals, reconstruct images, and produce quantitative metrics, such as FAZ area, will greatly improve the efficiency and standardization of results between studies. Most importantly, clinical trial protocols should account for the relatively high frequency of poor-quality data related to sub-optimal imaging conditions in DR and should incorporate time for assessing OCTA image quality and re-imaging patients where necessary.

CGMap: Characterizing continuous glucose monitor data in thousands of non-diabetic individuals

Despite its rising prevalence, diabetes diagnosis still relies on measures from blood tests. Technological advances in continuous glucose monitoring (CGM) devices introduce a potential tool to expand our understanding of glucose control and variability in people with and without diabetes. Yet CGM data have not been characterized in large-scale healthy cohorts, creating a lack of reference for CGM data research. Here we present CGMap, a characterization of CGM data collected from over 7,000 non-diabetic individuals, aged 40-70 years, between 2019 and 2022. We provide reference values of key CGM-derived clinical measures that can serve as a tool for future CGM research. We further explored the relationship between CGM-derived measures and diabetes-related clinical parameters, uncovering several significant relationships, including associations of mean blood glucose with measures from fundus imaging and sleep monitoring. These findings offer novel research directions for understanding the influence of glucose levels on various aspects of human health.

The Impact of Image Processing Algorithms on Optical Coherence Tomography Angiography Metrics and Study Conclusions in Diabetic Retinopathy

Purpose

The purpose of this study was to evaluate the impact of image processing on quantitative metrics in optical coherence tomography angiography (OCTA) images and study conclusions in patients with diabetes.

Methods

This was a single center, retrospective cross-sectional study. OCTA imaging with the Cirrus HD-OCT 5000 AngioPlex of patients with diabetes was performed. The 8 × 8 mm superficial slab images underwent 4 different preprocessing methods (none, background subtraction [BGS], foveal avascular zone brightness adjustment, and contrast limited adaptive histogram equalization [CLAHE]) followed by 4 different binarization algorithms (global Huang, global Otsu, local Niblack, and local Phansalkar) in ImageJ. Vessel density (VD), skeletonized VD (SVD), and fractal dimension (FD) were calculated. Mixed-effect multivariate linear regressions were performed.

Results

Two hundred eleven scans from 104 patients were included. Of these scans, 67 (31.8%) had no diabetic retinopathy (DR), 99 (46.9%) had nonproliferative DR (NPDR), and 45 (21.3%) had proliferative DR (PDR). Forty-eight of 211 (22.7%) scans had diabetic macular edema (DME). The image processing method used significantly impacted values of VD, SVD, and FD (all P -values < 0.001). On multivariate analysis, the image processing method changed the clinical variables significantly associated with VD, SVD, and FD. However, BGS and CLAHE yielded more consistent significant covariates across multiple binarization algorithms.

Conclusions

The image processing method can impact the conclusions of any given study analyzing quantitative OCTA metrics. Thus, caution is urged in the interpretation of such studies. Background subtraction or CLAHE may play a role in the standardization of image processing.

Translational Relevance

This work proposes strategies to achieve robust and consistent analysis of OCTA imaging, which is especially important for 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.

MULTISCALE CORRELATION OF MICROVASCULAR CHANGES ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY WITH RETINAL SENSITIVITY IN DIABETIC RETINOPATHY

PURPOSE

To assess global, zonal, and local correlations between vessel density changes measured by optical coherence tomography angiography and retinal sensitivity measured by microperimetry across diabetic retinopathy severity.

METHODS

Diabetic patients and nondiabetic controls underwent optical coherence tomography angiography imaging and microperimetry testing. Pearson's correlation was used to assess associations between average sensitivity and skeletonized vessel density (SVD) or foveal avascular zone area centrally. Linear mixed effects modeling was used to assess relationships between local SVD measurements and their spatially corresponding retinal sensitivity measurements.

RESULTS

Thirty-nine eyes from 39 participants were imaged. In all slabs, there was a statistically significant positive correlation between retinal sensitivities and SVDs on both global and zonal scales. No statistically significant correlation was found between central retinal sensitivities and the foveal avascular zone areas. Assessment of 1,136 spatially paired retinal sensitivity and SVD measurements revealed a statistically significant local relationship; this seemed to be driven by eyes with proliferative diabetic retinopathy that had reduced retinal sensitivities.

CONCLUSION

This study supports positive correlations between SVD and retinal sensitivity at global and zonal spatial scales in diabetic eyes. However, our analysis did not find evidence of statistically significant correlations between retinal sensitivity and SVD on a local scale until advanced diabetic retinopathy.

Differentiating features of OCT angiography in diabetic macular edema

The purpose of current study was to evaluate different optical coherence tomography angiography (OCTA) metrics in eyes with diabetic retinopathy with and without diabetic macular edema (DME). In this retrospective study, macular OCTA images of eyes with non-proliferative or proliferative diabetic retinopathy were evaluated. Vascular density, vascular complexity and non-perfusion densities were compared between eyes with and without DME. One-hundred-thirty-eight eyes of 92 diabetic patients including 49 eyes with DME were included. In multivariate analysis, the presence of DME was positively associated with geometric perfusion deficit (GPD) in superficial capillary plexus (SCP), capillary non-perfusion (CNP) of SCP, and GPD in deep capillary plexus (DCP) (all P < 0.05). In eyes with DME, central foveal thickness was associated with VD ratio (SCP/DCP) (P = 0.001) and FAZ area (P = 0.001). In conclusion, in eyes with diabetic retinopathy, the presence of DME was associated with more extensive capillary non-perfusion compared to those with no macular edema.