Diabetic retinopathy and OCT angiography: clinical findings and future perspectives

Harnessing deep learning for detection of diabetic retinopathy in geriatric group using optical coherence tomography angiography-OCTA: A promising approach

The prevalence of diabetic retinopathy (DR) among the geriatric population poses significant challenges for early detection and management. Optical Coherence Tomography Angiography (OCTA) combined with Deep Learning presents a promising avenue for improving diagnostic accuracy in this vulnerable demographic. In this method, we propose an innovative approach utilizing OCTA images and Deep Learning algorithms to detect diabetic retinopathy in geriatric patients. We have collected 262 OCTA scans of 179 elderly individuals, both with and without diabetes, and trained a deep-learning model to classify retinopathy severity levels. Convolutional Neural Network (CNN) models: Inception V3, ResNet-50, ResNet50V2, VggNet-16, VggNet-19, DenseNet121, DenseNet201, EfficientNetV2B0, are trained to extract features and further classify them. Here we demonstrate:•The potential of OCTA and Deep Learning in enhancing geriatric eye care at the very initial stage.•The importance of technological advancements in addressing age-related ocular diseases and providing reliable assistance to clinicians for DR classification.•The efficacy of this approach in accurately identifying diabetic retinopathy stages, thereby facilitating timely interventions, and preventing vision loss in the elderly population.

Polarization-resolved analysis of outer retinal bands: investigating ballistic and multiply scattered photons using full-field swept-source optical coherence tomography

Precise interpretation of the anatomical origins of outer retinal optical coherence tomography (OCT) presents technical challenges owing to the delicate nature of the retina. To address this challenge, our study introduces a novel polarization-sensitive full-field swept-source OCT (FF-SS-OCT) that provides parallel-polarization and cross-polarization OCT measurements, predominantly capturing ballistically reflected photons and multiply scattered photons, respectively. Notably, parallel-polarization OCT unveils layer-like structures more effectively, including the inner plexiform layer (IPL) sub-layers, outer plexiform layer (OPL) sub-layers (in rod-dominant regions), and rod/cone outer segment (OS) tips, compared to cross-polarization OCT, where such sub-layers are not visible. Through a comparative analysis of parallel-polarization and cross-polarization OCT images of the outer retina, we discovered that the 2nd outer retinal OCT band results from contributions from both the ellipsoid zone (EZ) and the inner segment/outer segment (IS/OS) junction. Similarly, the 3rd outer retinal OCT band appears to reflect contributions from both the interdigitation zone (IZ) and photoreceptor OS tips. This polarization-sensitive approach advances our understanding of the origins of outer retinal OCT signals and proposes potential new biomarkers for assessing retinal health and diseases.

Optical coherence tomography angiography macular biomarkers of peripheral retinal ischemia in diabetic macular edema: secondary endpoints from the clinical study "FOVEA"

PURPOSE

To investigate the relationship between the macular values of fractal dimension (FD) and lacunarity (LAC) on optical coherence tomography angiography (OCTA) images and the presence of peripheral retina non-perfusion areas (NPAs) on fluorescein angiography (FA) in patients with treatment-naïve diabetic macular edema (DME).

METHODS

Fifty patients with treatment-naïve DME underwent a full ophthalmic examination, including best-corrected visual acuity measurement, FA, spectral-domain optical coherence tomography, and OCTA. Specifically, FA was performed to detect the presence of retinal NPAs, whereas fractal OCTA analysis was used to determine macular FD and LAC values at the level of the superficial and deep capillary plexus (SCP and DCP). FA montage frames of the posterior pole and peripheral retina, as well as macular OCTA slabs of the SCP and DCP, were obtained.

RESULTS

Thirty (60%) eyes with FA evidence of peripheral retinal NPAs in at least one quadrant showed significantly lower FD and higher LAC in both SCP and DCP, when compared with eyes presenting a well-perfused peripheral retina. Furthermore, macular FD and LAC values were found to be significantly associated with the extent of retinal NPAs.

CONCLUSIONS

Macular FD and LAC of both SCP and DCP seem to be strongly associated with the extent of peripheral retinal NPAs, thus suggesting that may be useful predictive biomarkers of peripheral ischemia in treatment-naïve DME eyes.

The clinical evaluation of a widefield lens to expand the field of view in optical coherence tomography (OCT-A)

This study aimed to evaluate the clinical benefits of incorporating a widefield lens (WFL) in optical coherence tomography angiography (OCT-A) in patients with retinal vascular diseases in comparison to standard single-shot OCT-A scans. Sixty patients with retinal vascular diseases including diabetic retinopathy (DR) and retinal vein occlusion (RVO) were recruited. OCT-A imaging (PlexElite 9000) with and without WFL was performed in randomized order. The assessment included patient comfort, time, field of view (FoV), image quality and pathology detection. Statistical analysis included paired t-tests, Mann-Whitney U-tests and Bonferroni correction for multiple tests, with inter-grader agreement using the kappa coefficient. Using a WFL did not lead to statistically significant differences in DR and RVO group test times. Patient comfort remained high, with similar responses for WFL and non-WFL measurements. The WFL notably expanded the scan field (1.6× FoV increase), enhancing peripheral retinal visibility. However, image quality varied due to pathology and eye dominance, affecting the detection of peripheral issues in RVO and DR cases. The use of a WFL widens the scan field, aiding vascular retinal disease imaging with minor effects on comfort, time, and image quality. Further enhancements are needed for broader view angles, enabling improved quantification of non-perfused areas and more reliable peripheral proliferation detection.

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.

Clinical and Translational Imaging and Sensing of Diabetic Microangiopathy: A Narrative Review

Microvascular changes in diabetes affect the function of several critical organs, such as the kidneys, heart, brain, eye, and skin, among others. The possibility of detecting such changes early enough in order to take appropriate actions renders the development of appropriate tools and techniques an imperative need. To this end, several sensing and imaging techniques have been developed or employed in the assessment of microangiopathy in patients with diabetes. Herein, we present such techniques; we provide insights into their principles of operation while discussing the characteristics that make them appropriate for such use. Finally, apart from already established techniques, we present novel ones with great translational potential, such as optoacoustic technologies, which are expected to enter clinical practice in the foreseeable future.

Multiple instance learning based classification of diabetic retinopathy in weakly-labeled widefield OCTA en face images

Diabetic retinopathy (DR), a pathologic change of the human retinal vasculature, is the leading cause of blindness in working-age adults with diabetes mellitus. Optical coherence tomography angiography (OCTA), a functional extension of optical coherence tomography, has shown potential as a tool for early diagnosis of DR through its ability to visualize the retinal vasculature in all spatial dimensions. Previously introduced deep learning-based classifiers were able to support the detection of DR in OCTA images, but require expert labeling at the pixel level, a labor-intensive and expensive process. We present a multiple instance learning-based network, MIL-ResNet,14 that is capable of detecting biomarkers in an OCTA dataset with high accuracy, without the need for annotations other than the information whether a scan is from a diabetic patient or not. The dataset we used for this study was acquired with a diagnostic ultra-widefield swept-source OCT device with a MHz A-scan rate. We were able to show that our proposed method outperforms previous state-of-the-art networks for this classification task, ResNet14 and VGG16. In addition, our network pays special attention to clinically relevant biomarkers and is robust against adversarial attacks. Therefore, we believe that it could serve as a powerful diagnostic decision support tool for clinical ophthalmic screening.

OCT Angiography Features in Diabetes Mellitus Type 1 and 2

Purpose: To study the foveal avascular zone (FAZ) and the vessel densities (VD) in diabetic patients using optical coherence tomography angiography (OCT-A) and inner retinal layer changes to compare patients affected by type 1 diabetes (DM1) and type 2 diabetes (DM2). Methods: Cross-sectional observational study involving 150 eyes of 150 patients with DM1, and 155 eyes of 155 patients with DM2 with diabetic retinopathy (DR). Retinal nerve fiber layer (RNFL) and Ganglion cell layer (GCL) were evaluated. OCT-A studied both FAZ and VD at the level of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP). Results: A statistically significant difference in FAZ area and foveal VD measured at the SCP (p < 0.001) was noted between DM1 and DM2 groups when comparing patients with mild and moderate non-proliferative diabetic retinopathy (NPDR), while no differences were found in the severe NPDR and proliferative diabetic retinopathy (PDR) subgroups. Duration of diabetes and stage of DR were directly correlated with enlargement of FAZ area and inversely correlated with foveal VD measured at SCP. RNFL and GCL were not different between DM1 and DM2 groups. Conclusion: Changes in OCT-A parameters detected in FAZ area and VD of diabetic patients with different stages of DR may help to predict the risk for progression of the disease.

Early Retinal Microvasculopathy in Prediabetic Patients and Correlated Factors

INTRODUCTION

We aimed to detect early retinal microcirculation changes in prediabetic patients and investigate their correlation with clinical examinations.

METHODS

Forty-seven prediabetic individuals, 29 controls, and 81 type 2 diabetic mellitus (T2DM) patients were enrolled in this study. A review of clinical data and spectral-domain optical coherence tomography angiography (SD-OCTA) parameters of macular vessel diameter (VD), foveal avascular zone (FAZ), and macular vessel area density (VAD) was performed.

RESULTS

Levels of low-density lipoprotein cholesterol and triglycerides in prediabetes and T2DM groups were significantly higher than those in the control group. The urine microalbumin-to-creatinine ratio (ACR) was mildly and moderately increased in the prediabetes and T2DM groups, respectively. The estimated glomerular filtration rate of the three groups was within the normal range. SD-OCTA showed that VAD in the superficial macular area was decreased in the prediabetes group compared to the control group (p = 0.01). The FAZ size, particularly in the deep layer, was expanded in the prediabetes group. In the deep retinal layer of the macular area, VD and FAZ size in the prediabetes group were larger than those in the control group. In the prediabetes group, the axial length was significantly correlated with macular VD and FAZ size (p < 0.05), and ACR was correlated with FAZ size (p < 0.05). Age had a negative correlation with VAD (p < 0.01). ACR had a positive correlation with FAZ size (p < 0.05).

CONCLUSIONS

Enlargement and irregularity of the FAZ area, deep capillary dilation, and a decrease in VAD occur in the retina of prediabetic patients with mild kidney function impairment.

Visible Light Optical Coherence Tomography Reveals the Relationship of the Myoid and Ellipsoid to Band 2 in Humans

Purpose

We employ visible light optical coherence tomography (OCT) to investigate the relationship between the myoid, ellipsoid, and band 2 in the living human retina. Rather than refute existing theories, we aim to reveal new bands and better delineate the structures at hand.

Methods

An upgraded spectral/Fourier domain visible light OCT prototype, with 1.0-µm axial resolution, imaged 13 eyes of 13 young adult human subjects (23–40 years old) without a history of ocular pathology. The external limiting membrane (band 1) and band 2 edges were segmented. Reflectivity was examined along the inner segment (IS), defined as extending from band 1 to the band 2 center, and within band 2 itself.

Results

Images highlight a nearly continuously resolved extrafoveal internal limiting membrane, the peripheral single-cell thick ganglion cell layer, and the peripheral photoreceptor axonal fiber layer, a peripheral division of band 2 into bands 2a and 2b, and a reflectivity-based division of the IS into “m” and “e” zones.

Discussion

Topography and transverse intensity variations of the outermost band 2b suggest an association with rods. The “m” and “e” zone border is consistent with the myoid–ellipsoid boundary, even recapitulating the well-documented distribution of mitochondria throughout the IS at the foveal center. Theories of outer retinal reflectivity in OCT must adequately explain these observations.

Translational Relevance

Findings support that band 2 does partially overlap with the ellipsoid in transversally averaged OCT images due to photoreceptor IS length dispersion but argue that the inner ellipsoid must be inner to band 2, as suggested by prior quantitative measurements.

HORNBILL: a phase I/IIa trial examining the safety, tolerability and early response of BI 764524 in patients with diabetic retinopathy and diabetic macular ischaemia-rationale, study design and protocol

Background

Diabetic macular ischaemia (DMI) is a complication of diabetic retinopathy that leads to irreversible vision loss. DMI is characterised by reduced retinal vessel density and enlargement of the foveal avascular zone (FAZ). Despite its clinical burden, there is no formal consensus on the definition of DMI, and no approved treatment. Semaphorin 3A (Sema3A) is an axonal guidance molecule that blocks revascularisation of the ischaemic retina. Sema3A modulation is therefore a promising mechanism of action for the treatment of ischaemic eye diseases. BI 764524 is an intravitreal anti-Sema3A ischaemia modulator agent.

Methods

HORNBILL (NCT04424290) is a phase I/IIa trial comprising a non-randomised, open-label, single rising dose (SRD) part and a randomised, masked, sham-controlled multiple dose (MD) part to investigate the safety, tolerability and early biological response of ischaemia modulator BI 764524 in adults (≥18 years) with DMI. DMI will be defined using optical coherence tomography angiography (OCTA) as either any degree of disruption in the retinal vascularity (SRD) or a FAZ of ≥0.5 mm² (MD). Subjects in the SRD part will receive 0.5, 1.0 or 2.5 mg of BI 764524; the maximum tolerated dose will then be used in the MD part. A minimum of 12 subjects will be enrolled into the SRD part; planned enrollment is 30 for the MD part. The primary endpoint of the SRD part is the number of subjects with dose-limiting adverse events (AEs) until day 8. The primary endpoint of the MD part is the number of subjects with drug-related AEs from baseline to end of study, and secondary endpoints include change from baseline in the size of the FAZ, best-corrected visual acuity and central retinal thickness.

Discussion

DMI is a poorly defined condition with no treatment options. HORNBILL is the first clinical trial to assess a treatment for DMI and to use OCTA as a means to define and examine DMI. The OCTA data generated in this trial could form the basis of formal diagnostic criteria for DMI. Furthermore, the novel mechanism of action (Sema3A modulation) explored in this trial has the potential to revolutionise the treatment landscape for patients with DMI.

Trial registration

ClinicalTrials.govNCT04424290; EudraCT 2019-004432-28. Registered on 9 June 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06527-y.

Subcellular Comparison of Visible-Light Optical Coherence Tomography and Electron Microscopy in the Mouse Outer Retina

Purpose

We employed in vivo, 1.0-µm axial resolution visible-light optical coherence tomography (OCT) and ex vivo electron microscopy (EM) to investigate three subcellular features in the mouse outer retina: reflectivity oscillations inner to band 1 (study 1); hyperreflective band 2, attributed to the ellipsoid zone or inner segment/outer segment (IS/OS) junction (study 2); and the hyperreflective retinal pigment epithelium (RPE) within band 4 (study 3).

Methods

Pigmented (C57BL/6J, n = 10) and albino (BALB/cJ, n = 3) mice were imaged in vivo. Enucleated eyes were processed for light and electron microscopy. Using well-accepted reference surfaces, we compared micrometer-scale axial reflectivity of visible-light OCT with subcellular organization, as revealed by 9449 annotated EM organelles and features across four pigmented eyes.

Results

In study 1, outer nuclear layer reflectivity peaks coincided with valleys in heterochromatin clump density (-0.34 ± 2.27 µm limits of agreement [LoA]). In study 2, band 2 depth on OCT and IS/OS junction depth on EM agreed (-0.57 ± 0.76 µm LoA), with both having similar distributions. In study 3, RPE electron dense organelle distribution did not agree with reflectivity in C57BL/6J mice, with OCT measures of RPE thickness exceeding those of EM (2.09 ± 0.89 µm LoA). Finally, RPE thickness increased with age in pigmented mice (slope = 0.056 µm/mo; P = 6.8 × 10-7).

Conclusions

Visible-light OCT bands arise from subcellular organization, enabling new measurements in mice. Quantitative OCT-EM comparisons may be confounded by hydration level, particularly in the OS and RPE. Caution is warranted in generalizing results to other species.

Living Without a Diagnosis: A Patient's Perspective on Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy (DR) that can result in progressive and irreversible vision loss. DMI is associated with damage in the vessels that supply blood to the retina and the enlargement of the foveal avascular zone. Currently, there are no approved treatments specifically for DMI. Furthermore, there is limited published information about the prognosis, prevalence or outcomes of DMI, and there is no consensus regarding diagnostic criteria. It is vital to ensure that there is sufficient, accessible and accurate information available to support patients, caregivers and physicians. To lay the foundation for more research into DMI and its impact on patients, we (a patient with DMI and an expert ophthalmologist) have worked together to interweave our personal perspectives and clinical experiences with a review of currently available literature on DMI. The development of a set of confirmed diagnostic criteria for DMI would assist both patients and physicians, allowing patients to access validated information about their condition and supporting the development of clinical trials for treatments of DMI. Training for physicians must continue to emphasise the importance of treating a patient holistically, rather than only treating their symptoms. Most importantly, developing trust and a healthy rapport between a patient and their physician is important in managing health anxiety and ensuring adherence to beneficial treatments or lifestyle adjustments; physicians must cultivate an open and flexible management approach with their patients. Finally, holistic educational programmes for patients, physicians and the general public around DMI and how it can affect daily functioning would facilitate general understanding and disease awareness.

Diabetic macular ischemia (DMI) is a common problem for patients with diabetic retinopathy that can lead to sight loss. There is very little information available about DMI, particularly from a patient’s point of view. To address the lack of information about DMI, we (a person with DMI and her eye doctor) have worked together to examine what it is like to live with DMI. It is important to provide clear and accessible information about diseases to patients and carers. The lack of information about DMI may be upsetting for some people, and should be addressed with more research. Developing of a set of confirmed signs and symptoms for the diagnosis of DMI would allow people to be more confident in the information that they receive about their disease, and support the development of treatments for DMI. The support of others is central to the wellbeing of people with vision loss. Although people with vision loss may also lose independence, care from loved ones can help to improve quality of life. Most importantly, developing trust between a patient and their doctor is central to managing people’s fears about their eyesight, and making sure that they follow helpful advice. Doctors must use an open and flexible approach with their patients, providing information in an honest and understandable way.

OCT Angiography as an Interdisciplinary Diagnostic Tool for Systemic Diseases

In recent years, OCT angiography (OCT-A) has emerged as a well established imaging modality of the retina. This allows non-invasive visualisation of the retinal circulation at a micrometre scale in eye disorders and systemic diseases with potential ocular involvement. This review summarises the current state of this topic.

Update on Optical Coherence Tomography and Optical Coherence Tomography Angiography Imaging in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a major cause of blindness in diabetic individuals. Optical coherence tomography (OCT) and OCT-angiography (OCTA) are noninvasive imaging techniques useful for the diagnosis and assessment of PDR. We aim to review several recent developments using OCT and discuss their present and potential future applications in the clinical setting. An electronic database search was performed so as to include all studies assessing OCT and/or OCTA findings in PDR patients published from 1 January 2020 to 31 May 2021. Thirty studies were included, and the most recently published data essentially focused on the higher detection rate of neovascularization obtained with widefield-OCT and/or OCTA (WF-OCT/OCTA) and on the increasing quality of retinal imaging with quality levels non-inferior to widefield-fluorescein angiography (WF-FA). There were also significant developments in the study of retinal nonperfusion areas (NPAs) using these techniques and research on the impact of PDR treatment on NPAs and on vascular density. It is becoming increasingly clear that it is critical to use adequate imaging protocols focused on optimized segmentation and maximized imaged retinal area, with ongoing technological development through artificial intelligence and deep learning. These latest findings emphasize the growing applicability and role of noninvasive imaging in managing PDR with the added benefit of avoiding the repetition of invasive conventional FA.

PRE-RETINOPATHY OF TYPE 1 DIABETES IN THE CONTEXT OF FUNCTIONAL, STRUCTURAL AND MICROCIRCULATORY CHANGES IN THE MACULAR AREA

AIM

The authors assessed the development of intraocular changes in type 1 diabetes (T1DM) from the onset of the disease leading to diabetic retinopathy (DR). The quote: &#8220;There must be an intermediate stage between the physiological intraocular finding and the diabetic retinopathy itself &#8220;, (prof. Jan Vav&#345;inec).

METHODS

A two-year study (2018 and 2019) was conducted at the Department of Ophthalmology of the Teaching Hospital Kralovske Vinohrady in Prague (Czech Republic). There were 54 patients aged 17-42 years, the detection of T1DM ranged between the 1st and 14th year of life, with a duration of 12-35 years. Individual patients were always examined simultaneously by three methods: CS (contrast sensitivity), SD-OCT (spectral domain optical coherence tomography) and OCT-A (optical coherence tomography-angiography). We examined 106 eyes once and in a comprehensive manner.

RESULTS

We have shown that there is an intermediate stage between the physiological finding on the retina and DR, so-called diabetic pre-retinopathy (DpR). Subsequent redistribution of the observed into two DpR subgroups was derived from the size of the FAZ, either with its smaller area or with a larger area determining the microvascularity of the central area of the retina. The results of both other methods were assigned to these values. For SD-OCT, the depth of the fovea (the difference between the central retinal thickness and the total average retinal thickness) was determined, which was affected by the increased the macular cubature. In all patients it was on average 10.3 &#956;m3. The retina in the central area was significantly strengthened compared to the healthy population at the level of significance p 0,001. We divided the actual DpR into an image: DpR1 in 26.5 % of eyes - condition with an average shallower fovea only by 21.5 &#956;m below the level of the surrounding retina and an average narrower FAZ: 0.165 mm2 and with a more significant decrease in CS; DpR2 in 40.5 % of eyes - condition with average deeper fovea by 42 &#956;m, i.e., more significantly and average larger FAZ: 0.325 mm2 with lower decrease of CS. At the same time, other changes in microvascularity were noted, such as disorders in the sense of non-perfusion in the central part of the retina of various degrees. This finding differed significantly from changes in already established (non-proliferative) NPDR in 36 % of eyes, when a significant decrease in CS with normal visual acuity was found 4/4 ETDRS. Statistical differences in CS between DpR1 and DpR2 and NPDR were determined - always p 0.001. The average depth of the fovea was NPDR: 29.5 &#956;m. NPDR had the largest average FAZ: 0.56 mm2. Also significant were the most significant changes in non-perfusion and especially the presence of microaneurysms.

CONCLUSIONS

These three non - invasive methods helped to monitor the dynamics of the development of ocular changes in T1DM of better quality than the determination of visual acuity and ophthalmoscopic examination. Increased retinal volume induced hypoxia of visual cells with subsequent dual autoregulatory mechanism conditioning two types of diabetic pre-retinopathy before the onset of DR.

Visfatin promotes angiogenesis of RF/6A cells through upregulation of VEGF/VEGFR-2 under high-glucose conditions

Visfatin is a type of adipocytokine that is highly expressed in the serum and vitreous of patients with diabetic retinopathy. The purpose of the present study was to investigate the effect and mechanism of visfatin on angiogenesis in RF/6A monkey chorioretinal retinal endothelial cells under high glucose (HG) conditions in vitro. RF/6A cells were randomly divided into four groups: Control group, under high glucose (HG) group (25 mM D-glucose), visfatin group 1 (10 nM visfatin + 25 mM D-glucose), visfatin group 2 (20 nM visfatin + 25 mM D-glucose) and visfatin group 3 (30 nM visfatin + 25 mM D-glucose). After 24 and 48 h, a Cell Counting Kit-8, wound-healing assay and Matrigel tube formation assay were used to detect cell proliferation, migration and cell tube formation, respectively. Subsequently, the expression levels of VEGF and VEGF receptor 2 (VEGFR-2) in cells of visfatin group 3 were observed by western blot and reverse transcription-quantitative PCR analyses. At 24 and 48 h, the cell proliferation and migration distance in the HG group were reduced compared with those in the control group (P<0.05). Compared with those in the HG group, the cell proliferation and migration distance in all visfatin groups were significantly increased (P<0.05), with the highest significance in visfatin group 3. Visfatin significantly promoted tube-like structure formation by RF/6A cells, particularly at the concentration of 30 nM. The protein and mRNA expression levels of VEGF and VEGFR-2 were significantly increased in the HG group as compared with those in the control group (P<0.05). Furthermore, compared with those in the HG group, VEGF and VEGFR-2 protein and mRNA expression levels were significantly increased in visfatin group 3 (P<0.05). Overall, visfatin promoted the proliferation, migration and tube formation of RF/6A cells under HG conditions, suggesting that visfatin has a potent effect on retinal neovascularization and its mechanism may be associated with the promotion of VEGF and VEGFR-2 expression under HG conditions.

Large-cube 30° × 25° optical coherence tomography in diabetic macular edema

Background

To evaluate the contribution of large-cube 30° × 25° optical coherence tomography (OCT) in the characterization of diabetic macular edema (DME) by assessing its extent and the presence of additional retinal edemas and to evaluate the factors that influenced their occurrence.

Methods

This retrospective study enrolled patients with diabetes who presented with retinal edema detected by horizontal large-cube 30° × 25° (8.7 × 7.3 mm) OCT. Two individualized areas were selected from the thickness map: the area within the 6-mm Early Treatment of Diabetic Retinopathy Study (ETDRS) grid, and that outside the ETDRS grid. Retinal edemas located within the ETDRS grid were designated as “main DME” and those located outside the ETDRS grid were designated as “peripheral retinal edemas.” For each area, OCT features were assessed while the extent of the main DME and the presence of peripheral retinal oedema were analysed in the area outside the ETDRS grid. Finally, part of included eyes was followed by the same protocol, of which a part benefited from intravitreal injections.

Results

Peripheral events were detected outside the ETDRS area in 279 eyes (74.4%) of the 375 eyes of the 218 patients included in this study: an extension of the main DME outside ETDRS grid in 177 eyes (47.2%) and/or the presence of peripheral retinal edemas in 207 eyes (55.2%). The analysis of associations between main DME and peripheral retinal edemas patterns did not find an association for retinal cyst localization (P = 0.42) while a week association was found fort cyst size (Cramer’s V = 0.188, p = 0.028). Nevertheless, a moderate association was found for the presence of microaneurysms (Cramer’s V = 0.247, p < 0.001) and strong association for hard exudates (Cramer’s V = 0.386, p < 0.001), The binary logistic regression analysis retained the following influencing factors of the occurrence of peripheral events: advanced DR stage (Odds ratio OR = 2.19, p = 0.03), diffuse DME (OR = 7.76, p < 0.001) and its location in outer fields (OR = 7.09, p = 0.006). Likewise, the extension of the main DME outside the ETDRS area in was influenced by the same factors in addition to CMT (OR = 0.98, p = 0.004) while the presence of peripheral retinal edema was influenced by the same factors except the outer location of the Main DME. Finally, from the 94 eyes treated by intravitreal injections, extension of the main DME outside the ETDRS grid was detected in 54 eyes (56.44%) at baseline visit and still remained detectable in 37 eyes (39.36%) after treatment initiation.

Conclusions

Large-cube 30° × 25° OCT allowed for more precise assessment of DME extension and better detection of retinal thickening mainly in the advanced stages of diabetic retinopathy with significant DME whether at the baseline visit or during follow-up. The combination of this protocol with a wider ETDRS grid would enhance DME detection and topography.

Looking Ahead: Visual and Anatomical Endpoints in Future Trials of Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy that can lead to progressive and irreversible visual loss. Despite substantial clinical burden, there are no treatments for DMI, no validated clinical trial endpoints, and few clinical trials focusing on DMI. Therefore, generating consensus on validated endpoints that can be used in DMI for the development of effective interventions is vital. In this review, we discuss potential endpoints appropriate for use in clinical trials of DMI, and consider the data required to establish acceptable and meaningful endpoints. A combination of anatomical, functional, and patient-reported outcome measures will provide the most complete picture of changes that occur during the progression of DMI. Potential endpoint measures include change in size of the foveal avascular zone measured by optical coherence tomography angiography and change over time in best-corrected visual acuity. However, these endpoints must be supported by further research. We also recommend studies to investigate the natural history and progression of DMI. In addition to improving understanding of how patient demographics and comorbidities such as diabetic macular edema affect clinical trial endpoints, these studies would help to build the consensus definition of DMI that is currently missing from clinical practice and research.

Analyzing Relative Flow Speeds in Diabetic Retinopathy Using Variable Interscan Time Analysis OCT Angiography

PURPOSE

Further insight into the flow characteristics of the vascular features associated with diabetic retinopathy (DR) may improve assessment and treatment of disease progression. The variable interscan time analysis (VISTA) algorithm is an extension of OCT angiography (OCTA) that detects relative blood flow speeds, which then can be depicted on a color-coded map. This study used VISTA to analyze relative blood flow speeds in the microvascular changes associated with DR.

DESIGN

Cross-sectional study.

PARTICIPANTS

Thirteen patients with varying severities of DR treated at New England Eye Center, Boston, Massachusetts.

METHODS

OCT angiography images centered at the fovea were obtained on a prototype swept-source OCT device, and the VISTA algorithm was applied to visualize relative blood flow speeds.

MAIN OUTCOME MEASURES

Descriptive flow analysis of the retinal vascular features of DR was conducted on the VISTA-generated images.

RESULTS

Twenty-six eyes were included in this study. Of these, 3 eyes had mild nonproliferative DR (NPDR), 6 eyes had moderate NPDR, 4 eyes had severe NPDR, 9 eyes had proliferative DR, and 4 eyes were normal controls. Microaneurysms, intraretinal microvascular abnormalities (IRMAs), and neovascularization appeared to originate from areas of relatively slow blood flow speeds. Microaneurysms showed relatively slower flow, IRMAs showed turbulent, intermediate to slow flow, and venous beading and looping presented with relatively high flow speeds that tapered progressively. Neovascularization of venous origin demonstrated slower flow speeds, whereas that of arterial origin showed relatively high flow speeds. Additionally, increased disease severity was associated with globally slower flow speeds, with particularly slower flow around the foveal avascular zone.

CONCLUSIONS

The VISTA algorithm seems to be a useful extension of OCTA that overcomes some of the limitations of normal gray-scale OCTA. It seems to have some potential in providing relevant insight into the pathogenesis of the microvascular changes associated with DR. These findings may assist in improving our understanding of the pathogenic changes that take place in DR.

Foveal avascular zone analysis by optical coherence tomography angiography in patients with type 1 and 2 diabetes and without clinical signs of diabetic retinopathy

PURPOSE

To analyze the early macular microvascular alterations in patients with type 1 and 2 diabetes mellitus (DM) without diabetic retinopathy (DR), using optical coherence tomography angiography (OCT-A), and compare these with nondiabetic patients.

METHODS

This prospective study involved 93 patients with type 1 diabetes (DM1), 104 patients with type 2 diabetes (DM2) without signs of DR, and 71 healthy subjects for the control group. The foveal avascular zone (FAZ) area and the vessel density (VD) at the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were evaluated.

RESULTS

The SCP and DCP FAZ areas were significantly larger in the DM1 group in comparison with the controls (p = .001), while no significant differences were observed between the DM2 group and the healthy control group (p = .12). Additionally, no significant differences in FAZ area were found between the DM1 and DM2 groups (p = .26). The VD was significantly reduced in DM1 and DM2 groups compared to controls. A direct correlation was found between the duration of diabetes and SCP FAZ area (r = 0.44; R² = 0.19; p = .0001). Statistically significant differences in the FAZ area at SCP and DCP were observed when comparing patients with a diabetes duration > 10 years and < 10 years in the DM2 group (p = .0001, respectively) and only in the FAZ area at the DCP in the DM1 group (p = .0001).

CONCLUSION

Diabetic patients without DR demonstrate early microvascular alteration in the macular area on OCT-A, which is more pronounced in type I DM, and correlates with the duration of the disease.

Markedly decreasing incidence of cause-specific blindness in Saxony (Eastern Germany)

PURPOSE

To analyze the recent time trend in Saxony.

METHODS

Data were based on administrative files in Saxony (Eastern Germany) to assess recipients of blindness allowance newly registered between January 1, 2009, and December 31, 2017. We estimated age-sex standardized incidence of all-cause and cause-specific blindness and used Poisson regression to examine age- and sex-adjusted time trends.

RESULTS

We identified 5114 new cases of blindness (63.3% female, 59.9% ≥ 80 years). We observed a markedly decrease in incidence of blindness: all-causes 2009: 15.7 per 100,000 person years [95% confidence interval: 14.6-17.0]; 2017: 8.9 [8.1-9.8]; age-related macular degeneration 2009: 6.9 [6.1-7.7], 2017: 3.8 [3.3-4.3]; glaucoma 2009: 2.6 [2.2-3.1], 2017: 1.8 [1.4-2.2]; diabetic retinopathy 2009: 1.5 [1.2-1.9], 2017: 0.7 [0.5-1.0]; myopia 2009: 0.7 [0.5-1.1], 2017: 0.4 [0.2-0.5]; optic atrophy 2009: 0.9 [0.6-1.2], 2017: 0.5 [0.3-0.7]; and cataract 2009: 0.5 [0.3-0.8], 2017: 0.1 [0.1-0.3]. The annual reduction was between 5 (glaucoma, relative risk 0.95 [0.92-0.98]) and 16% (cataract, relative risk 0.84 [0.78-0.91]).

CONCLUSION

The age- and sex-standardized incidence of blindness decreased among all common causes of blindness in Saxony in the last decade.

The 100 Most Cited Articles in Ophthalmology in Asia

PURPOSE

The aim of this study was to review the top 100 most-cited articles in ophthalmology in Asia since 1970.

METHODS

The Scopus database was used to identify the top 100 most-cited ophthalmology articles published in ophthalmology (T100-Eye) and nonophthalmology (T100-General) journals.

RESULTS

The T100-Eye articles were published between 1982 and 2015, and T100-General from 1982 to 2017. T100-Eye had higher citations [median (range) = 317 (249-1326)] than T100-General [158 (105-2628)], but T100-General were published in journals with higher impact factor (IF) than T100-Eye (median IF= 5.5 vs 4.4) and produced more landmark papers (3 vs 1 articles that were cited >1000 times). Fifty-five % of T100-Eye were published in 3 journals: Ophthalmology (n = 22), Investigative Ophthalmology and Visual Science (n = 17), and American Journal of Ophthalmology (n = 16). T100-Eye had 88 original research articles and 12 reviews, whereas T100-General had 84 original research and 16 reviews. The most-frequent studied disease categories were myopia (n = 16) and age-related macular degeneration (n = 15) in T100-Eye and diabetic retinopathy (n = 24) and glaucoma (n = 16) in T100-General. Japan and Singapore contributed most to T100-Eye (n = 42, n = 17) and T100-General (n = 36, n = 26) articles. More than 80% and 95% of first and last authors were male in both lists. Emerging research topics were optical coherence tomography in T100-Eye and artificial intelligence in T100-General.

CONCLUSIONS

Our citation analysis reveals differences in the focus of research topics of top-cited ophthalmology articles published in ophthalmology and nonophthalmology journals in Asia. It highlights that certain eye diseases are studied more in Asia and shows the contribution of specific countries to highly cited publications in ophthalmology research in Asia.

Optical coherence tomography features of neovascularization in proliferative diabetic retinopathy: a systematic review

Background

Diabetic retinopathy (DR) is a leading cause of blindness due to diabetic macular edema (DME) or complications of proliferative diabetic retinopathy (PDR). Optical coherence tomography (OCT) is a noninvasive imaging technique well established for DME but less used to assess neovascularization in PDR. Developments in OCT imaging and the introduction of OCT angiography (OCTA) have shown significant potential in PDR.

Objectives

To describe the tomographic features of PDR, namely of neovascularization, both of the optic disc (NVD) and elsewhere (NVE), intraretinal microvascular abnormalities (IRMA), retinal nonperfusion areas (NPA), status of the posterior vitreous, vitreoschisis and vitreous and subhyaloid/sub-ILM hemorrhages.

Data sources

Electronic database search on PubMed and EMBASE, last run on December 19th 2019.

Study eligibility criteria, participants and interventions

Publications assessing OCT and/or OCTA findings in PDR patients. All study designs were allowed except for case-reports, conference proceedings and letters.

Study appraisal

Newcastle–Ottawa Scale for observational studies was used for purposes of risk of bias assessment.

Results

From the 1300 studies identified, 283 proceeded to full-text assessment and 60 were included in this comprehensive review. OCT was useful in detecting NVD and NVE, such as in characterizing disease activity and response to laser and/or anti-VEGF therapies. The absence of posterior vitreous detachment seemed determinant for neovascular growth, with the posterior hyaloid acting as a scaffold. OCTA allowed a more detailed characterization of the neovascular complexes, associated NPA and disease activity, allowing the quantification of neovessel area and flow index. However, changes in OCTA blood flow signal following local therapies did not necessarily correlate with structural regression. Widefield and ultra-widefield OCTA were highly sensitive in the detection of PDR, adding value to disease staging and monitoring. Compared to fluorescein angiography, OCTA was more sensitive in detecting microvascular changes indicating disease progression.

Limitations

Publication languages were restricted. Most included studies were observational and non-comparative. Risk of bias regarding case representativeness.

Conclusions

OCT-based retinal imaging technologies are advancing rapidly and the trend is to be noninvasive and wide-field. OCT has proven invaluable in diagnosing, staging and management of proliferative diabetic disease with daily application in clinical and surgical practices.

Prospective, Single-Center, Six-Month Study of Intravitreal Ranibizumab for Macular Edema with Nonproliferative Diabetic Retinopathy: Effects on Microaneurysm Turnover and Non-Perfused Retinal Area

Purpose

To analyze the effects on microaneurysm (MA) and perifoveal perfusion in nonproliferative diabetic retinopathy (NPDR) patients with macular edema (ME) after early intensive treatment using intravitreal ranibizumab (IVR) injections.

Patients and Methods

Prospectively, 25 eyes of 25 type 2 diabetes mellitus patients with ME were included between August 2016 and February 2019. For 6 months, patients were administered 0.5-mg IVR injections monthly. Ocular evaluation, including best-corrected visual acuity (BCVA; using the Early Treatment Diabetic Retinopathy Study chart), central retinal thickness (CRT; using optical coherence tomography), fundus photography, and fluorescein angiography, was performed for all participants. Results obtained at baseline were compared to those observed after 6 months.

Results

Mean BCVA increased significantly from 67.6±3.29 letters at baseline to 76.36±1.61 letters after 6 months (P=0.002) of IVR therapy. CRT decreased significantly from 479.12±16.66 µm at baseline to 369.12±13.02 µm at 6 months. Similarly, the total number of MAs decreased significantly from 5.68±3.41 to 1.60±1.73 (P<0.0001). MA turnover, calculated by adding the MA formation rate to the MA disappearance rate (both calculated as MA number/month) also decreased significantly from 6.88±3.83 to 1.92±1.75 after treatment (P<0.0001). Perifoveal non-perfused area decreased from 2.517±0.456 mm² at baseline to 2.495±0.293 mm² at 6 months, but the results were not statistically significant (P=0.954).

Conclusion

Treatment with early intensive IVR therapy in NPDR patients with ME not only improved BCVA and CRT but also decreased MA turnover. However, in the study period of 6 months, IVR therapy did not show significant improvement in perifoveal non-perfused area.

Correlations Between Optical Coherence Tomography Angiography Parameters and the Visual Acuity in Patients with Diabetic Retinopathy

Aim

The aim of this study was to assess the correlation between different optical coherence tomography angiography (OCTA) parameters and the best corrected visual acuity (BCVA) in patients with diabetic retinopathy (DR).

Patients and Methods

Sixty eyes of 60 participants were included in this prospective study: 40 diabetic patients [20 with non-proliferative diabetic retinopathy (NPDR group), 20 with proliferative diabetic retinopathy (PDR group)] and 20 age- and gender-matched normal healthy subjects (control group). After full ophthalmological examination and fundus fluorescein angiography, OCTA was performed for all participants. Quantitative OCTA parameters, such as the foveal avascular zone (FAZ) area, the superficial capillary plexus vessel density (%) (SCP-VD) and the deep capillary plexus vessel density (%) (DCP-VD) in, whole and parafoveal areas were measured. Correlations between BCVA and OCTA parameters were analyzed.

Results

There were no statistically significant differences between groups regarding age, gender, refraction, macular thickness or intraocular pressure. The median (IQR) FAZ area was 0.42 (0.39–0.46) mm² in the NPDR group, 0.54 (0.45–0.65) mm² in the PDR group and 0.24 (0.21–0.26) mm² in the control group (P<0.001). The FAZ area increased with increasing severity of DR. SCP-VD and DCP-VD showed significant differences between groups (P<0.001). Vessel density (VD) was decreased in both DCP and SCP as DR progressed. There was a significant positive correlation between BCVA (LogMAR) and FAZ area. There were significant negative correlations between BCVA (LogMAR) and VD in both SCP and DCP. Stepwise multiple linear regression analysis demonstrated that SCP-VD in the whole area and DCP-VD in the parafoveal area were the best predictive factors for BCVA in the NPDR and PDR groups.

Conclusion

With progression of DR, the VD decreased and the FAZ area increased, and both parameters were correlated with poor visual acuity. OCTA is a non-invasive tool which can be used to detect diabetic macular ischemia and help in the prediction of visual prognosis.

Associations between Macular OCT Angiography and Nonproliferative Diabetic Retinopathy in Young Patients with Type 1 Diabetes Mellitus

METHODS

OCTA of both eyes was performed in a cross-sectional study of 14 to 30-year-old individuals with at least 10-year duration of T1D and controls recruited from the Norwegian Atherosclerosis and Childhood Diabetes (ACD) study. Vessel density (VD) and foveal avascular zone (FAZ) area in the superficial and deep capillary plexus (SCP and DCP), total retinal volume (TRV), and central macular thickness (CMT) were calculated using automated software. Univariate and multivariate ordered logistic regression (OLR) models were used accordingly.

RESULTS

We included 168 control eyes and 315 T1D eyes. Lower VD in DCP (OR 0.65, 95% CI 0.51-0.83), longer diabetes duration (OR 1.51, 95% CI 1.22-1.87), and higher waist circumference (OR 1.08, 95% CI 1.02-1.14) were significantly associated with progression of NPDR. VD in SCP and DCP were significantly lower in T1D patients without diabetic retinopathy than in controls.

CONCLUSIONS

Sparser VD in DCP is significantly associated with severity of NPDR, supporting that OCTA might detect the earliest signs of NPDR before it is visible by ophthalmoscopy.

RETINAL MICROCIRCULATION INVESTIGATION IN TYPE I AND II DIABETIC PATIENTS WITHOUT RETINOPATHY USING AN ADAPTIVE OPTICS RETINAL CAMERA

CONTEXT

State of art imaging techniques might be a useful tool to early detect the retinal vessels lesions in diabetes.

OBJECTIVE AND DESIGN

This analytical observational study investigates the retinal microcirculation changes in type I and II diabetic patients without retinopathy using adaptive optics ophthalmoscopy (AOO) and optical coherence ophthalmoscopy angiography (OCTA).

SUBJECTS AND METHODS

Fifty-five subjects were included in this study and were divided in three groups: type I diabetic group (n=16), type II diabetic group (n=19) and control group (n=20). An adaptive optics retinal camera was used to assess the parameters of the temporal superior retinal arterioles. Moreover, vessel density of the superficial capillary plexus across the parafoveal area was measured with OCT-A. All cases were investigated once, in a cross-sectional design.

RESULTS

Diabetic patients from both groups had a higher wall-to-lumen-ratio compared to the controls (p=0.01 and 0.01, respectively). Interestingly, no significant differences were found between the two diabetic groups (p=0.69). Moreover, the vessel density was smaller in the type I diabetic group than in the control group (p=0.001).

CONCLUSION

AOO might be a useful tool to detect early retinal vascular changes in diabetes before any clinical signs and together with OCTA it might bring important information on the prognostic and pathophysiology of the disease.

[Diagnosis, treatment and monitoring of diabetic eye disease (Update 2019)]

Diabetes mellitus can cause diabetic retinopathy, diabetic macular edema, optic neuropathy, cataract or dysfunction of the eye muscles. The incidence of these defects correlates with disease duration and quality of metabolic control. Recommendations of the Austrian Diabetes Association for diagnosis, therapeutic procedures and requirements for adequate follow-up depending on stage of diabetic eye disease are summarized.

Prevalence and severity of diabetic retinopathy in patients attending the endocrinology diabetes clinic at Mulago Hospital in Uganda

AIMS

The epidemiology for diabetic retinopathy (DR) has been well described in the western population. Countries in Sub-Saharan Africa have attempted to identify the prevalence of diabetic eye disease, however, there still remains a degree of paucity across the continent due to inadequacy in health system organisations and resource poor settings. We aimed to identify the severity and prevalence of DR and maculopathy of patients attending the diabetes clinic at Mulago Hospital, Kampala, Uganda.

METHODS

A cross-sectional observational study of 44 patients who attended a diabetes clinic at Mulago Hospital in April 2016. Parameters measured included visual acuity (VA) using a Snellen chart, blood glucose (mmol/l) and blood pressure (mmHg). Screening for DR grading was carried out with indirect fundoscopy and retinal photograph. Only the highest graded eye of retinopathy of each patient was included.

RESULTS

A total of 41 eyes from 41 patients were included. Of these patients 15 were male. The average age of patients was 50.4 years. Six eyes (14.6%) had a VA < 6/18. Prevalence of DR was 19.5% (8 eyes) and 14.6% (6 eyes) had maculopathy. Of all eyes 14.6% had sight-threatening retinopathy, which was 85.7% of total cases of retinopathy in our study.

CONCLUSIONS

We observed a high prevalence of DR and maculopathy, particularly sight threatening retinopathy, considering the proportion of patients screened. There is a need for a co-ordinated diabetes screening service through integration of the diabetes clinic and eye clinic at Mulago Hospital to better identify and treat this sight-threatening condition.

Photothermal Optical Coherence Tomography of Anti-Angiogenic Treatment in the Mouse Retina Using Gold Nanorods as Contrast Agents

Purpose

Optical coherence tomography (OCT) is widely used for ocular imaging in clinical and research settings. OCT natively provides structural information based on the reflectivity of the tissues it images. We demonstrate the utility of photothermal OCT (PTOCT) imaging of gold nanorods (GNR) in the mouse retina in vivo in the laser-induced choroidal neovascularization (LCNV) model to provide additional image contrast within the lesion.

Methods

Wild-type C57BL/6 mice were imaged following the intravenous injection of ICAM2-targeted or untargeted GNR. Mice were also imaged following the injection of ICAM2-targeted GNR with or without the additional ocular delivery of a neutralizing monoclonal anti-vascular endothelial growth factor (anti-VEGF) antibody.

Results

Mice cohorts injected with untargeted or ICAM2-targeted GNR demonstrated increased lesion-associated photothermal signal during subsequent imaging relative to phosphate-buffered saline (PBS)-injected controls. Additionally, intravitreal injection of anti-VEGF antibody caused a detectable reduction in the extent of anatomic laser damage and lesion-associated photothermal signal density in mice treated in the LCNV model and injected with ICAM2-targeted GNR.

Conclusions

These experiments demonstrate the ability of PTOCT imaging of GNR to detect anti-VEGF-induced changes in the mouse retina using the LCNV model.

Translational Relevance

This study shows that PTOCT imaging of GNR in the LCNV model can be used to detect clinically relevant, anti-VEGF-induced changes that are not visible using standard OCT systems. In the future this technology could be used to aid in early detection of disease, monitoring disease progress, and assessing its response to therapies.

Quantitative Comparison of Retinal Vascular Features in Optical Coherence Tomography Angiography Images From Three Different Devices

BACKGROUND AND OBJECTIVE

To compare optical coherence tomography angiography (OCTA) images from three different devices.

PATIENTS AND METHODS

This was a prospective, observational, cross-sectional study. All eyes (n = 24) were imaged thrice each time with swept-source OCT (DRI OCT Triton Plus; Topcon, Tokyo, Japan), spectral-domain OCTA (AngioVue; Optovue, Fremont, CA), and SD-OCT Angioplex (Cirrus HD-OCT 5000; Carl Zeiss Meditec, Jena, Germany). Outcome measures were foveal avascular zone (FAZ) area, vessel density, spacing between large vessels (SLV), and spacing between small vessels (SSV). They were calculated using local fractal analyses and Frangi filter.

RESULTS

The vascular parameters showed good to excellent repeatability (intraclass coefficient > 0.8) in the three devices. The FAZ area (P = .3) and vessel density of the superficial layer (P = .8) were similar between the devices. In the deep layer, vessel density was significantly higher (P = .02) with Angio-Vue images compared to those acquired using the other devices. However, SLV was significantly higher (P < .05) and SSV was significantly lower (P < .05) on Angioplex scans compared to other devices. Vessel parameters were significantly altered in Frangi-filtered images as compared to nonfiltered images.

CONCLUSIONS

Vessel density showed good repeatability among the three devices, although there were differences in vessel parameters between the devices. Also, vessel parameters changed significantly after Frangi filtering. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:488-496.].

OCT Angiography: A Technique for the Assessment of Retinal and Optic Nerve Diseases in the Pediatric Population

Optical coherence tomography angiography (OCT-A) is a novel, rapidly evolving, non-invasive imaging technique that allows images of the retinal vasculature to be obtained in a few seconds. Blood vessels of different retinal vascular plexuses and the foveal avascular zone (FAZ) can be examined without the administration of any contrast or dye. Due to these characteristics, OCT-A could be an excellent complementary test to study retinal vascularization in children. Until now, most of the studies with OCT-A have been conducted in adults and only a few have been carried out in children. In this review, we describe the principles and advantages of OCT-A over traditional imaging methods and provide a summary of the OCT-A findings in retinopathy of prematurity and other retinal and optic disc pathologies in children. In view of the promising results from studies, the advantages of a relatively rapid and non-invasive method to assess the retinal vasculature makes OCT-A a tool of which applications in the field of pediatric ophthalmology will be expanded in the near future for patient diagnosis and follow-up in every day clinical practice.

Optical coherence tomography angiography (OCTA) flow speed mapping technology for retinal diseases

INTRODUCTION

Optical coherence tomography angiography (OCTA) is a noninvasive imaging modality for depth-resolved visualization of retinal vasculature. Angiographic data couples with structural data to generate a cube scan, from which en-face images of vasculature can be obtained at various axial positions. OCTA has expanded understanding of retinal vascular disorders and has primarily been used for qualitative analysis.

AREAS COVERED

Recent studies have explored the quantitative properties of OCTA, which would allow for objective assessment and follow-up of retinal pathologies. Various quantitative metrics have been developed, such as foveal avascular zone area and vessel density. However, quantitative assessment of the characteristics of retinal blood flow remains limited, as OCTA provides an image depicting either the presence or absence of flow at a particular region without information of relative velocities. The development of variable interscan time analysis (VISTA) overcomes this limitation. The VISTA algorithm generates a color-coded map of relative blood flow speeds. VISTA has already demonstrated utility in furthering our understanding of various retinal pathologies, such as geographic atrophy, choroidal neovascularization, aneurysmal type 1 neovascularization, and diabetic retinopathy.

EXPERT COMMENTARY

VISTA, an OCTA flow speed mapping technique, may have a role in developing the utility of OCTA as a screening tool.

Enhancement of morphological and vascular features in OCT images using a modified Bayesian residual transform

A novel image processing algorithm based on a modified Bayesian residual transform (MBRT) was developed for the enhancement of morphological and vascular features in optical coherence tomography (OCT) and OCT angiography (OCTA) images. The MBRT algorithm decomposes the original OCT image into multiple residual images, where each image presents information at a unique scale. Scale selective residual adaptation is used subsequently to enhance morphological features of interest, such as blood vessels and tissue layers, and to suppress irrelevant image features such as noise and motion artefacts. The performance of the proposed MBRT algorithm was tested on a series of cross-sectional and enface OCT and OCTA images of retina and brain tissue that were acquired in-vivo. Results show that the MBRT reduces speckle noise and motion-related imaging artefacts locally, thus improving significantly the contrast and visibility of morphological features in the OCT and OCTA images.

Comparison between optical coherence tomography angiography and fluorescein angiography findings in retinal vasculitis

Background

To describe optical coherence tomography angiography (OCT-A) findings in patients with retinal vasculitis and to compare them to current fluorescein angiography (FA) findings.

Methods

This was an observational case series. Nineteen eyes in 10 patients with retinal vasculitis of various etiologies were imaged with FA (TRC-50DX, Topcon) and OCT-A (SD-OCT, Optovue). The images were reviewed and analyzed.

Results

The mean age was 36 years (range 24-67 years); there were three males and seven females. The primary vessels involved were veins (89%). Fourteen eyes (74%) had active inflammatory disease during the study period, with signs of vascular sheathing and perivascular leakage on FA. Interestingly, in this group, OCT-A was not able to detect clear signs of active inflammation around the affected vessels. Nevertheless, OCT-A was able to detect secondary lesions in fourteen eyes (74%), including some findings not clearly shown on FA. Most of these were within the macular area. OCT-A was particularly effective in cases of capillary dropout, increased foveal avascular zone, telangiectasias, shunts, and areas of neovascularization.

Conclusion

FA remains an essential complementary exam for detection of retinal vasculitis. However, OCT-A extends FA findings and affords better assessment of secondary complications.

An Update on Optical Coherence Tomography Angiography in Diabetic Retinopathy

Optical coherence tomography angiography (OCTA) is a novel non-invasive imaging modality for 3-dimensional visualization of retinal and optic nerve capillary networks. In this article, a comprehensive review of relevant original articles in the PubMed database was performed using the search terms "diabetic retinopathy," "diabetic macular edema," "diabetes mellitus," and "optical coherence tomography angiography." OCTA was found to detect microvascular changes early in diabetes mellitus, even before they become clinically evident. Morphological and qualitative assessment of vascular changes can help to determine the pathophysiological processes, activity, treatment, and follow-up of diabetic retinopathy (DR). Vessel density and foveal avascular zone are the most investigated quantified indices shown to be early predictors of DR, correlated to DR severity and visual function, and useful in predicting response to treatment. OCTA has shown to be a promising alternative to fluorescein angiography in the management of DR. Further studies are warranted to determine the role of OCTA in the routine clinical management of DR.

Update on Diagnosis and Treatment of Diabetic Retinopathy: A Consensus Guideline of the Working Group of Ocular Health (Spanish Society of Diabetes and Spanish Vitreous and Retina Society)

A group of members of the Spanish Retina and Vitreous Society (SERV) and of the Working Group of Ocular Health of the Spanish Society of Diabetes (SED) updated knowledge regarding the diagnosis and treatment of diabetic retinopathy (DR) based on recent evidence reported in the literature. A synthesis of this consensus forms the basis of the present review, which is intended to inform clinicians on current advances in the field of DR and their clinical applicability to patients with this disease. Aspects presented in this article include screening procedures of DR, new technologies in the early diagnosis of DR, control of risk factors in the different stages of the disease, indications of panretinal laser photocoagulation, efficacy of intravitreal antiangiogenic agents and steroids, and surgical options for treating DR-related complications. Practical information regarding periodicity of screening procedures in patients with type 1 and type 2 diabetes, ophthalmological controls according to the stage of retinopathy and complications, and criteria and degree of urgency for referral of a DR patient to the ophthalmologist are also presented.