Detection rate of diabetic macular microaneurysms comparing dye-based angiography and optical coherence tomography angiography

Advances in OCT Angiography

Optical coherence tomography angiography (OCTA) is a signal processing and scan acquisition approach that enables OCT devices to clearly identify vascular tissue down to the capillary scale. As originally proposed, OCTA included several important limitations, including small fields of view relative to allied imaging modalities and the presence of confounding artifacts. New approaches, including both hardware and software, are solving these problems and can now produce high-quality angiograms from tissue throughout the retina and choroid. Image analysis tools have also improved, enabling OCTA data to be quantified at high precision and used to diagnose disease using deep learning models. This review highlights these advances and trends in OCTA technology, focusing on work produced since 2020.

Clinical Performance of Semi-Automated Spectral-Domain Optical Coherence Tomography Angiography

Background/Objectives: To evaluate the clinical performance of two optical coherence tomography angiography (OCTA) devices, including a semi-automated device, with respect to image quality and pathology detection, with fluorescein angiography (FA) and indocyanine green angiography (ICGA) serving as the reference standards. Methods: In this prospective cross-sectional study, normal eyes and those with various retinal and choroidal pathologies were enrolled and underwent OCTA scanning using semi-automated 3D OCT-1 Maestro2 and Cirrus™ HD-OCT 5000 devices, as well as FA/ICGA imaging. OCTA scans and FA/ICGA images were independently graded for image quality and the visibility of prespecified anatomic vascular features, along with the presence or absence of pathology on the OCTA scans and the FA/ICGA images (within regions corresponding to the OCTA scan areas). Positive percent agreement (PPA), defined as the proportion of eyes in which the OCTA demonstrated pathology when the corresponding FA/ICGA showed pathology, and negative percent agreement (NPA), defined as the proportion of eyes in which the OCTA showed no pathology when the FA/ICGA also showed no pathology, were calculated. Results: In total, 38 normal eyes and 86 pathologic eyes were enrolled in the study. The majority of images for both devices were considered clinically useful. The PPA and NPA were high for both devices, indicating a good ability to identify disease when present and to rule it out when not present. Conclusions: The findings of this study suggest that the semi-automated Maestro2 and Cirrus have comparably good clinical performance, particularly with regard to accuracy when identifying vascular pathologies.

Optical coherence tomography angiography for microaneurysms in anti-vascular endothelial growth factor treated diabetic macular edema

BACKGROUND

We aimed to evaluate microaneurysms (MAs) after treatment with anti-vascular endothelial growth factor (anti-VEGF) therapy to understand causes of chronic edema and anti-VEGF resistance.

METHODS

Patients with non-proliferative diabetic retinopathy, with or without macular edema were recruited. Optical coherence tomography angiography (OCTA) MAs-related parameters were observed, including the maximum diameter of overall dimensions, material presence, and flow signal within the lumen. OCTA parameters also included central macular thickness (CMT), foveal avascular zone, superficial and deep capillary plexuses, and non-flow area measurements on the superficial retinal slab.

RESULTS

Overall, 48 eyes from 43 patients were evaluated. CMT differed significantly between the diabetic macular edema (DME ) and non-DME (NDME) groups at 1st, 2nd, 3rd, and 6th months of follow-up (P < 0.001; <0.001; 0.003; <0.001, respectively). A total of 55 and 59 MAs were observed in the DME (mean = 99.40 ± 3.18 μm) and NDME (mean maximum diameter = 74.70 ± 2.86 μm) groups at baseline, respectively (significant between-group difference: P < 0.001). Blood flow signal was measurable for 46 (83.6%) and 34 (59.3%) eyes in the DME and NDME groups, respectively (significant between-group difference: P < 0.001).

CONCLUSIONS

Compared to the NDME group, the DME group had larger MAs and a higher blood-flow signal ratio. Following anti-VEGF therapy, changes in the diameter of MAs were observed before changes in CMT thickness.

Two cases of diabetic macular edema with diminished areas of retinal non-perfusion and microaneurysms after intravitreal faricimab injections

Purpose

To report two cases of diabetic macular edema (DME) treated with intravitreal faricimab injections (IVFs), including the assessment of retinal microaneurysms and extent of retinal capillary non-perfusion using fluorescein angiography (FA) and indocyanine green angiography (IA).

Observations

Case 1: A 72-year-old man presented with aflibercept-resistant DME in the left eye, with a best-corrected visual acuity (BCVA) of 20/16. FA showed areas of retinal capillary non-perfusion and focal leakage in the macular area of the left eye. IA revealed numerous microaneurysms in the temporal region of the macula. Four consecutive monthly IVFs were administered to the left eye, and DME eventually diminished. After the loading phase, the BCVA was maintained at 20/16 with reduced visual distortion. FA showed improvement of macular leakage and stable retinal capillary non-perfusion areas, and the foveal avascular zone was clearly observed. The disappearance of numerous microaneurysms was confirmed on IA images.Case 2: An 80-year-old woman developed DME with macular vein occlusion in the left eye after panretinal laser photocoagulation for proliferative diabetic retinopathy. The patient's BCVA was 20/32. DME was resistant to subtenon triamcinolone injections. FA revealed focal areas of retinal capillary non-perfusion and persistent leakage in the macular area of the left eye. IA revealed scattered microaneurysms within the retinal arcade. Four consecutive monthly IVFs were administered to the left eye, and DME eventually diminished. After the loading phase, the BCVA was maintained at 20/32. FA showed improvement of macular leakage and stable retinal capillary non-perfusion areas. The reduction of microaneurysms was confirmed on IA images.

Conclusions and importance

These case reports highlight the potential of faricimab as an alternative anti-vascular endothelial growth factor drug for treatment-resistant DME, including reduction of retinal microaneurysms and stabilization of the areas of retinal capillary non-perfusion. However, continuation of a robust treatment regimen may be required to achieve these objectives.

OCT angiography and its retinal biomarkers [Invited]

Optical coherence tomography angiography (OCTA) is a high-resolution, depth-resolved imaging modality with important applications in ophthalmic practice. An extension of structural OCT, OCTA enables non-invasive, high-contrast imaging of retinal and choroidal vasculature that are amenable to quantification. As such, OCTA offers the capability to identify and characterize biomarkers important for clinical practice and therapeutic research. Here, we review new methods for analyzing biomarkers and discuss new insights provided by OCTA.

Diabetic microaneurysms detected by fluorescein angiography spatially correlate with regions of macular ischemia delineated by optical coherence tomography angiography

PURPOSE

To characterize the relationship between diabetic macular ischemia (DMI) delineated by optical coherence tomography angiography (OCTA) and microaneurysms (MAs) identified by fundus fluorescein angiography (FFA).

METHODS

Patients with diabetic retinopathy (DR) who underwent OCTA and FFA were retrospectively identified. FFA images were cropped and aligned with their respective OCTA images using i2k Align Retina software (Dual-Align, Clifton Park, NY, USA). Foveal avascular zone (FAZ) and ischemic areas were manually delineated on OCTA images, and MAs were marked on the corresponding FFA images before overlaying paired scans for analysis (ImageJ; National Institutes of Health, Bethesda, MD, USA).

RESULTS

Twenty-eight eyes of 20 patients were included. The average number of MAs identified in cropped FFA images was 127 ± 42. More DMI was noted in the superficial capillary plexus (SCP; 36 ± 13%) compared to the deep capillary plexus (DCP; 28 ± 14%, P < 0.001). Similarly, more MAs were associated with ischemic areas in SCP compared to DCP (92.0 ± 35.0 vs. 76.8 ± 36.5, P < 0.001). Most MAs bordered ischemic areas; fewer than 10% localized inside these regions. As DMI area increased, so did associated MAs (SCP: r = 0.695, P < 0.001; DCP: r = 0.726, P < 0.001). Density of MAs surrounding FAZ (7.7 ± 6.0 MAs/mm2) was similar to other DMI areas (SCP: 7.0 ± 4.0 MAs/mm2, P = 0.478; DCP: 9.2 ± 10.9 MAs/mm2, P = 0.394).

CONCLUSION

MAs identified in FFA strongly associate with, and border areas of, DMI delineated by OCTA. Although more MAs are localized to SCP ischemia, the concentration of MAs associated with DCP ischemia is greater. By contrast, few MAs are present inside low-flow regions, likely because capillary loss is associated with their regression.

Deformable registration of multimodal retinal images using a weakly supervised deep learning approach

There are different retinal vascular imaging modalities widely used in clinical practice to diagnose different retinal pathologies. The joint analysis of these multimodal images is of increasing interest since each of them provides common and complementary visual information. However, if we want to facilitate the comparison of two images, obtained with different techniques and containing the same retinal region of interest, it will be necessary to make a previous registration of both images. Here, we present a weakly supervised deep learning methodology for robust deformable registration of multimodal retinal images, which is applied to implement a method for the registration of fluorescein angiography (FA) and optical coherence tomography angiography (OCTA) images. This methodology is strongly inspired by VoxelMorph, a general unsupervised deep learning framework of the state of the art for deformable registration of unimodal medical images. The method was evaluated in a public dataset with 172 pairs of FA and superficial plexus OCTA images. The degree of alignment of the common information (blood vessels) and preservation of the non-common information (image background) in the transformed image were measured using the Dice coefficient (DC) and zero-normalized cross-correlation (ZNCC), respectively. The average values of the mentioned metrics, including the standard deviations, were DC = 0.72  ±  0.10 and ZNCC = 0.82  ±  0.04. The time required to obtain each pair of registered images was 0.12 s. These results outperform rigid and deformable registration methods with which our method was compared.

Advances in application of swept-source optical coherence tomography angiography in diagnosis and treatment of diabetic retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of global blinding. More attention should be paid to the diagnosis, treatment and prognosis of DR. Swept-source optical coherence tomography angiography (SS-OCTA) is a novel imaging technique presented in recent years. It can accurately present the various levels of the retina, choriocapillaris, macula, and the optic papillary microcirculation, which is new to the diagnosis and prognosis of DR. However, SS-OCTA is limited by poor fixation or severe media clouding and is susceptible to motion artefacts and segmentation errors. Future limitations need to be addressed and large prospective trials conducted to refine the relevance of SS-OCTA to DR. The present study reviews the advances in clinical application of SS-OCTA in diagnosis, treatment and prognosis of DR.

Evaluation of microaneurysms as predictors of therapeutic response to anti-VEGF therapy in patients with DME

Administration of intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy is the first-line therapy for diabetic macular oedema (DME). However, some patients show no or insufficient response to repeated anti-VEGF injections. Therefore, it is necessary to identify factors that can predict this resistance against anti-VEGF treatment. Presence of microaneurysms (MAs) is a predictor of the development and progression of DME, but its relationship with the treatment response to the anti-VEGF agents is not well known. Therefore, we aimed to elucidate the relationship between the distribution of MAs and the response to anti-VEGF therapy in patients with DME. The number of MAs was measured before anti-VEGF therapy in each region using fluorescein angiography, indocyanine green angiography (IA), and optical coherence tomography angiography. Patients with DME were divided into the responder and non-responder groups after three loading phases. Differences in the distribution of MAs between the groups were investigated. Pre-treatment IA revealed more MAs in the nasal area in the non-responder group than in the responder group (10.7 ± 10.7 and 5.7 ± 5.7, respectively, in the nasal macula) (1.4 ± 2.1 and 0.4 ± 0.7, respectively, in the nasal fovea). Whereas, pre-treatment FA and OCTA could not reveal significantly difference between the groups. Detection of MAs in the nasal macula using pre-treatment IA may indicate resistance to anti-VEGF therapy. We recommend the clinicians confirm the presence of MAs in the nasal macula, as shown by IA, as a predictor of therapeutic response to anti-VEGF therapy in patients with treatment naive DME.

Studies of the retinal microcirculation using human donor eyes and high-resolution clinical imaging: Insights gained to guide future research in diabetic retinopathy

The microcirculation plays a key role in delivering oxygen to and removing metabolic wastes from energy-intensive retinal neurons. Microvascular changes are a hallmark feature of diabetic retinopathy (DR), a major cause of irreversible vision loss globally. Early investigators have performed landmark studies characterising the pathologic manifestations of DR. Previous works have collectively informed us of the clinical stages of DR and the retinal manifestations associated with devastating vision loss. Since these reports, major advancements in histologic techniques coupled with three-dimensional image processing has facilitated a deeper understanding of the structural characteristics in the healthy and diseased retinal circulation. Furthermore, breakthroughs in high-resolution retinal imaging have facilitated clinical translation of histologic knowledge to detect and monitor progression of microcirculatory disturbances with greater precision. Isolated perfusion techniques have been applied to human donor eyes to further our understanding of the cytoarchitectural characteristics of the normal human retinal circulation as well as provide novel insights into the pathophysiology of DR. Histology has been used to validate emerging in vivo retinal imaging techniques such as optical coherence tomography angiography. This report provides an overview of our research on the human retinal microcirculation in the context of the current ophthalmic literature. We commence by proposing a standardised histologic lexicon for characterising the human retinal microcirculation and subsequently discuss the pathophysiologic mechanisms underlying key manifestations of DR, with a focus on microaneurysms and retinal ischaemia. The advantages and limitations of current retinal imaging modalities as determined using histologic validation are also presented. We conclude with an overview of the implications of our research and provide a perspective on future directions in DR research.

Association of metformin treatment with enhanced effect of anti-VEGF agents in diabetic macular edema patients

PURPOSE

To investigate the effect of metformin combined with anti-VEGF agents in patients with diabetic macular edema (DME).

METHODS

This study was a prospective, nonrandomized case-control study. Patients were included in with a diagnosis of DME who received anti-VEGF agents injection. Basic information, medical history, best-corrected visual acuity (BCVA), central macular thickness (CMT), the number of intravitreal injections, panretinal photocoagulation (PRP), and macular grid photocoagulation treatment during the 6-month follow-up, were recorded for each patient.

RESULTS

A total of 50 DME patients were collected (24 patients with a history of oral metformin ≥ 6 months and 26 patients who had not taken metformin). The BCVA and the CMT were significantly improved after anti-VEGF treatment in two groups (F1 = 19.35, F2 = 26.78; F1 = 65.45, F2 = 76.23; P < 0.05). The BCVA in the metformin group was better than that in non-metformin group at every point after treatment (F = 34.45, P < 0.05). The CMT in metformin group decreased much more than that in non-metformin group during the follow-up period (F = 87.05, P < 0.05). The injection numbers decreased in the metformin group compared with the non-metformin group (t = 5.14, P < 0.05). However, there was no difference in PRP and macular grid photocoagulation therapy between the two groups during the 6-month follow-up.

CONCLUSION

Metformin can enhance the therapeutic effect of anti-VEGF agents on DME patients to improve their visual acuity, improve the structure of the macular area, and reduce the number of intravitreal injections 90.

Optical Coherence Tomography Angiography in Diabetic Patients: A Systematic Review

Background: Diabetic retinopathy (DR) is the leading cause of legal blindness in the working population in developed countries. Optical coherence tomography (OCT) angiography (OCTA) has risen as an essential tool in the diagnosis and control of diabetic patients, with and without DR, allowing visualisation of the retinal and choroidal microvasculature, their qualitative and quantitative changes, the progression of vascular disease, quantification of ischaemic areas, and the detection of preclinical changes. The aim of this article is to analyse the current applications of OCTA and provide an updated overview of them in the evaluation of DR. Methods: A systematic literature search was performed in PubMed and Embase, including the keywords “OCTA” OR “OCT angiography” OR “optical coherence tomography angiography” AND “diabetes” OR “diabetes mellitus” OR “diabetic retinopathy” OR “diabetic maculopathy” OR “diabetic macular oedema” OR “diabetic macular ischaemia”. Of the 1456 studies initially identified, 107 studies were screened after duplication, and those articles that did not meet the selection criteria were removed. Finally, after looking for missing data, we included 135 studies in this review. Results: We present the common and distinctive findings in the analysed papers after the literature search including the diagnostic use of OCTA in diabetes mellitus (DM) patients. We describe previous findings in retinal vascularization, including microaneurysms, foveal avascular zone (FAZ) changes in both size and morphology, changes in vascular perfusion, the appearance of retinal microvascular abnormalities or new vessels, and diabetic macular oedema (DME) and the use of deep learning technology applied to this disease. Conclusion: OCTA findings enable the diagnosis and follow-up of DM patients, including those with no detectable lesions with other devices. The evaluation of retinal and choroidal plexuses using OCTA is a fundamental tool for the diagnosis and prognosis of DR.

[Microaneurysms as a biomarker of diabetic retinopathy]

Diabetic retinopathy is a microvascular pathology, which is the most common complication of diabetes mellitus. Improvement of instrumental diagnostics of retinal pathologies has contributed to identification of various phenotypes of the progression of ocular fundus pathology in diabetes based on specific changes in the retina - biomarkers. In particular, microaneurysms initially described in diabetes, which are a manifestation of a wide range of systemic pathologies and retinal diseases, are an indicator of the severity of diabetic retinopathy. Dynamic changes in the number of microaneurysms are a confirmed prognostic biomarker of clinically significant macular edema. In diabetic retinopathy, microaneurysms are one of the earliest recognizable signs, and the dynamic of their formation and disappearance may serve as a predictor for the disease progression. This literature review presents the characteristics of microaneurysms based on various imaging techniques, and analyses the link between structural features and dynamic changes in microaneurysms, and progression of diabetic retinopathy.

Robust multimodal registration of fluorescein angiography and optical coherence tomography angiography images using evolutionary algorithms

Optical coherence tomography angiography (OCTA) and fluorescein angiography (FA) are two different vascular imaging modalities widely used in clinical practice to diagnose and grade different relevant retinal pathologies. Although each of them has its advantages and disadvantages, the joint analysis of the images produced by both techniques to analyze a specific area of the retina is of increasing interest, given that they provide common and complementary visual information. However, in order to facilitate this analysis task, a previous registration of the pair of FA and OCTA images is desirable in order to superimpose their common areas and focus the gaze on the regions of interest. Normally, this task is manually carried out by the expert clinician, but it turns out to be tedious and time-consuming. Here, we present a three-stage methodology for robust multimodal registration of FA and superficial plexus OCTA images. The first one is a preprocessing stage devoted to reducing the noise and segmenting the main vessels in both types of images. The second stage uses the vessel information to do an approximate registration based on template matching. Lastly, the third stage uses an evolutionary algorithm based on differential evolution to refine the previous registration and obtain the optimal registration. The method was evaluated in a dataset with 172 pairs of FA and OCTA images, obtaining a success rate of 98.8%. The best mean execution time of the method was less than 5 s per image.