Agreement between OCT Leakage and Fluorescein Angiography to Identify Sites of Alteration of the Blood-Retinal Barrier in Diabetes

Characterization of central-involved diabetic macular edema using OCT and OCTA

PURPOSE

To characterize the occurrence of diabetic macular edema and the presence of abnormal retinal fluid accumulation in nonproliferative diabetic retinopathy (NPDR).

METHODS

In this two-year prospective study, a total of 122 eyes with diabetes type 2 underwent optical coherence tomography (OCT) and OCT-Angiography in association with OCT-Fluid imaging, a novel algorithm of OCT analysis allowing quantification of abnormal accumulation of fluid in the retina through low optical reflectivity ratios (LOR). Early Treatment Diabetic Retinopathy Study (ETDRS) grading for diabetic retinopathy (DR) severity assessment was performed using 7-field color fundus photography. Best corrected visual acuity was also recorded.

RESULTS

During the 2-year follow-up, 23 eyes (19%) developed central-involved diabetic macular edema (CI-DME) and 2 eyes (2%) developed clinically significant macular edema (CSME). In the two-year period of the study, eyes that developed CI-DME showed a progressive increase in central retinal thickness (CRT) (β = 7.7 ± 2.1 µm/year, p < 0.001) and in LOR values (β = 0.009 ± 0.004 ratio/year, p = 0.027). The increase in CRT and abnormal retinal fluid, represented by increased LOR ratios, are associated with increased retinal perfusion in the deep capillary plexus (DCP) (skeletonized vessel density, p = 0.039). In contrast, the eyes with CSME showed decreased retinal perfusion and abnormal fluid located in the outer layers of the retina.

CONCLUSIONS

CI-DME and CSME appear to represent different entities. Eyes with CI-DME show increases in abnormal retinal fluid associated with increased retinal vascular perfusion in the DCP. Eyes with CSME are apparently associated with decreased retinal vascular perfusion in the DCP and abnormal fluid in the outer retina.

Clearance of interstitial fluid (ISF) and CSF (CLIC) group-part of Vascular Professional Interest Area (PIA), updates in 2022-2023. Cerebrovascular disease and the failure of elimination of Amyloid-β from the brain and retina with age and Alzheimer's disease: Opportunities for therapy

This editorial summarizes advances from the Clearance of Interstitial Fluid and Cerebrospinal Fluid (CLIC) group, within the Vascular Professional Interest Area (PIA) of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment (ISTAART). The overarching objectives of the CLIC group are to: (1) understand the age-related physiology changes that underlie impaired clearance of interstitial fluid (ISF) and cerebrospinal fluid (CSF) (CLIC); (2) understand the cellular and molecular mechanisms underlying intramural periarterial drainage (IPAD) in the brain; (3) establish novel diagnostic tests for Alzheimer's disease (AD), cerebral amyloid angiopathy (CAA), retinal amyloid vasculopathy, amyloid-related imaging abnormalities (ARIA) of spontaneous and iatrogenic CAA-related inflammation (CAA-ri), and vasomotion; and (4) establish novel therapies that facilitate IPAD to eliminate amyloid β (Aβ) from the aging brain and retina, to prevent or reduce AD and CAA pathology and ARIA side events associated with AD immunotherapy.

Assessment of Inner Blood-Retinal Barrier: Animal Models and Methods

Proper functioning of the neural retina relies on the unique retinal environment regulated by the blood-retinal barrier (BRB), which restricts the passage of solutes, fluids, and toxic substances. BRB impairment occurs in many retinal vascular diseases and the breakdown of BRB significantly contributes to disease pathology. Understanding the different molecular constituents and signaling pathways involved in BRB development and maintenance is therefore crucial in developing treatment modalities. This review summarizes the major molecular signaling pathways involved in inner BRB (iBRB) formation and maintenance, and representative animal models of eye diseases with retinal vascular leakage. Studies on Wnt/β-catenin signaling are highlighted, which is critical for retinal and brain vascular angiogenesis and barriergenesis. Moreover, multiple in vivo and in vitro methods for the detection and analysis of vascular leakage are described, along with their advantages and limitations. These pre-clinical animal models and methods for assessing iBRB provide valuable experimental tools in delineating the molecular mechanisms of retinal vascular diseases and evaluating therapeutic drugs.

Perspectives of diabetic retinopathy-challenges and opportunities

Diabetic retinopathy (DR) may lead to vision-threatening complications in people living with diabetes mellitus. Decades of research have contributed to our understanding of the pathogenesis of diabetic retinopathy from non-proliferative to proliferative (PDR) stages, the occurrence of diabetic macular oedema (DMO) and response to various treatment options. Multimodal imaging has paved the way to predict the impact of peripheral lesions and optical coherence tomography-angiography is starting to provide new knowledge on diabetic macular ischaemia. Moreover, the availability of intravitreal anti-vascular endothelial growth factors has changed the treatment paradigm of DMO and PDR. Areas of research have explored mechanisms of breakdown of the blood-retinal barrier, damage to pericytes, the extent of capillary non-perfusion, leakage and progression to neovascularisation. However, knowledge gaps remain. From this perspective, we highlight the challenges and future directions of research in this field.

Characterisation of progression of macular oedema in the initial stages of diabetic retinopathy: a 3-year longitudinal study

BACKGROUND/OBJECTIVES

To characterise the prevalence and three-year progression of centre-involving diabetic macular oedema (CI-DMO) in minimal to moderate non-proliferative diabetic retinopathy, using optical coherence tomography (OCT) and measurements of retinal fluid using tissue optical reflectivity ratios (OCT-Leakage).

METHODS/METHODS

Seventy-four eyes from 74 patients were followed in a 3-year prospective longitudinal observational cohort of type 2 diabetes (T2D) patients using spectral-domain optical coherence tomography (SD-OCT), OCT-Angiography (OCT-A) and OCT-Leakage (OCT-L). Eyes were examined four times with 1-year intervals. Sixteen eyes (17.8%) were excluded from the analysis due to quality control standards. Retinal oedema was measured by central retinal thickness and retinal fluid by using optical reflectivity ratios obtained with the OCT-L algorithm. Vessel density was measured by OCT-A. Thinning of the ganglion cell and inner plexiform layers (GCL + IPL) was examined to identify retinal neurodegenerative changes. Diabetic retinopathy ETDRS classification was performed using the seven-field ETDRS protocol.

RESULTS

CI-DMO was identified in the first visit in 9% of eyes in ETDRS groups 10-20, 10% of eyes in ETDRS group 35 and 15% of eyes in ETDRS groups 43-47. The eyes with CI-DMO and subclinical CI-DMO showed a progressive increase in retinal extracellular fluid during the 3-year period of follow-up. The eyes with CI-DMO and increased retinal extracellular fluid accumulation were associated with vision loss.

CONCLUSIONS

The prevalence of subclinical CI-DMO and CI-DMO in the initial stages of NPDR occurs independently of severity grading of the retinopathy, showing progressive increase in retinal extracellular fluid and this increase is associated with vision loss (82% 9 out of 11 cases).

Retinal Vasculopathy in Alzheimer's Disease

The retina has been increasingly investigated as a site of Alzheimer’s disease (AD) manifestation for over a decade. Early reports documented degeneration of retinal ganglion cells and their axonal projections. Our group provided the first evidence of the key pathological hallmarks of AD, amyloid β-protein (Aβ) plaques including vascular Aβ deposits, in the retina of AD and mild cognitively impaired (MCI) patients. Subsequent studies validated these findings and further identified electroretinography and vision deficits, retinal (p)tau and inflammation, intracellular Aβ accumulation, and retinal ganglion cell-subtype degeneration surrounding Aβ plaques in these patients. Our data suggest that the brain and retina follow a similar trajectory during AD progression, probably due to their common embryonic origin and anatomical proximity. However, the retina is the only CNS organ feasible for direct, repeated, and non-invasive ophthalmic examination with ultra-high spatial resolution and sensitivity. Neurovascular unit integrity is key to maintaining normal CNS function and cerebral vascular abnormalities are increasingly recognized as early and pivotal factors driving cognitive impairment in AD. Likewise, retinal vascular abnormalities such as changes in vessel density and fractal dimensions, blood flow, foveal avascular zone, curvature tortuosity, and arteriole-to-venule ratio were described in AD patients including early-stage cases. A rapidly growing number of reports have suggested that cerebral and retinal vasculopathy are tightly associated with cognitive deficits in AD patients and animal models. Importantly, we recently identified early and progressive deficiency in retinal vascular platelet-derived growth factor receptor-β (PDGFRβ) expression and pericyte loss that were associated with retinal vascular amyloidosis and cerebral amyloid angiopathy in MCI and AD patients. Other studies utilizing optical coherence tomography (OCT), retinal amyloid-fluorescence imaging and retinal hyperspectral imaging have made significant progress in visualizing and quantifying AD pathology through the retina. With new advances in OCT angiography, OCT leakage, scanning laser microscopy, fluorescein angiography and adaptive optics imaging, future studies focusing on retinal vascular AD pathologies could transform non-invasive pre-clinical AD diagnosis and monitoring.

OPTICAL COHERENCE TOMOGRAPHY LEAKAGE IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: Identification of Choroidal Neovascularization Activity by Location and Quantification of Abnormal Fluid Under Anti-Vascular Endothelial Growth Factor Therapy

This study shows that optical coherence tomography leakage can identify and locate choroidal neovascularization–related abnormal fluid and its change after anti–vascular endothelial growth factor treatment in neovascular age-related macular degeneration eyes. Low optical reflectivity ratio correlates with functional outcome and may be a marker of early choroidal neovascularization reactivation. Simultaneous optical coherence tomography angiography examination provides a noninvasive analysis of fluid and choroidal neovascularization vascular morphology.

Purpose:

To test optical coherence tomography leakage in the identification and quantification of choroidal neovascularization–related fluid, its change after anti–vascular endothelial growth factor therapy in neovascular age-related macular degeneration eyes and its relation to functional outcome.

Methods:

Prospective analysis of a cohort of neovascular age-related macular degeneration cases treated with 2.0-mg intravitreal aflibercept. Eyes included were analyzed before, 1-week, and 1-month after one injection. Best-corrected visual acuity was assessed using Early Treatment Diabetic Retinopathy Study method. Optical coherence tomography leakage maps depicting low optical reflectivity (LOR) sites were acquired with OCT Cirrus AngioPlex (Zeiss, Dublin, CA). The LOR area ratio was correlated to retinal thickness and best-corrected visual acuity. Optical coherence tomography angiography was simultaneously performed.

Results:

Twenty-two eyes of 18 patients with neovascular age-related macular degeneration were included. The LOR ratio of the full retina scan and retinal pigment epithelium–Bruch layer decreased from baseline to Month 1 (P < 0.05). Changes in retinal thickness and LOR ratio were positively correlated (P < 0.05). Best-corrected visual acuity change correlated with the outer segment layer LOR change (rho = −0.53, P = 0.014), and LOR was inferior in better responders (P = 0.021). Optical coherence tomography leakage identified eyes with recurrent fluid in the external layers.

Conclusion:

Optical coherence tomography leakage identified and quantified the fluid related to choroidal neovascularization activity. Low optical reflectivity change in the outer segment layer correlates with functional outcome and increasing LOR in the external layers may be a marker of early recurrence. Combining optical coherence tomography angiography and optical coherence tomography leakage allows both for choroidal neovascularization morphology and activity analysis.

Trends in optical coherence tomography angiography use in university clinic and private practice setting between 2014-2018

BACKGROUND

The aim was to assess the trends in optical coherence tomography angiography (OCTA) use compared with fluorescein angiography (FA).

METHODS

A bilateral patient's exam on a single day was considered one examination. A total of 3680 and 700 OCTA examinations and 3387 and 439 FA examinations were performed between 2014 and 2018 in a university clinic and private practice, respectively. A regression analysis was completed.

RESULTS

The use of OCTA procedures grew 17-fold from 2015 till 2018. In a university clinic, ultrawide-field FA accounted for 2% of all FA examinations performed in 2015, and its use increased to 68% in 2018 while the number of narrow-field FA examinations dropped from 617 in 2014 to 220 in 2018. This decrease inversely correlated with the rise of diabetic retinopathy cases diagnosed with FA (R= -0.86, p= 0.02). In private practice, the increase in the use of OCTA was a primary driver of the decline of the FA use from 127 in 2015 to 27 in 2018, while the number of OCTA examinations was 344 in 2018 (R= -0.99, p= 0.06).

CONCLUSION

The results of the study indicate that OCTA is a valuable tool capable of replacing FA in some selected cases.

Alzheimer's Retinopathy: Seeing Disease in the Eyes

The neurosensory retina emerges as a prominent site of Alzheimer's disease (AD) pathology. As a CNS extension of the brain, the neuro retina is easily accessible for noninvasive, high-resolution imaging. Studies have shown that along with cognitive decline, patients with mild cognitive impairment (MCI) and AD often suffer from visual impairments, abnormal electroretinogram patterns, and circadian rhythm disturbances that can, at least in part, be attributed to retinal damage. Over a decade ago, our group identified the main pathological hallmark of AD, amyloid β-protein (Aβ) plaques, in the retina of patients including early-stage clinical cases. Subsequent histological, biochemical and in vivo retinal imaging studies in animal models and in humans corroborated these findings and further revealed other signs of AD neuropathology in the retina. Among these signs, hyperphosphorylated tau, neuronal degeneration, retinal thinning, vascular abnormalities and gliosis were documented. Further, linear correlations between the severity of retinal and brain Aβ concentrations and plaque pathology were described. More recently, extensive retinal pericyte loss along with vascular platelet-derived growth factor receptor-β deficiency were discovered in postmortem retinas of MCI and AD patients. This progressive loss was closely associated with increased retinal vascular amyloidosis and predicted cerebral amyloid angiopathy scores. These studies brought excitement to the field of retinal exploration in AD. Indeed, many questions still remain open, such as queries related to the temporal progression of AD-related pathology in the retina compared to the brain, the relations between retinal and cerebral changes and whether retinal signs can predict cognitive decline. The extent to which AD affects the retina, including the susceptibility of certain topographical regions and cell types, is currently under intense investigation. Advances in retinal amyloid imaging, hyperspectral imaging, optical coherence tomography, and OCT-angiography encourage the use of such modalities to achieve more accurate, patient- and user-friendly, noninvasive detection and monitoring of AD. In this review, we summarize the current status in the field while addressing the many unknowns regarding Alzheimer's retinopathy.

Novel imaging biomarkers in diabetic retinopathy and diabetic macular edema

Diabetic retinopathy is one of the major microvascular complications of diabetes mellitus. The most common causes of vision loss in diabetic retinopathy are diabetic macular edema and proliferative diabetic retinopathy. Recent developments in ocular imaging have played a significant role in early diagnosis and management of these complications. Color fundus photography is an imaging modality, which is helpful for screening patients with diabetic eye disease and monitoring its progression as well as response to treatment. Fundus fluorescein angiography (FFA) is a dye-based invasive test to detect subtle neovascularization, look for areas of capillary non-perfusion, diagnose macular ischemia, and differentiate between focal and diffuse capillary bed leak in cases of macular edema. Recent advances in retinal imaging like the introduction of spectral-domain and swept source-based optical coherence tomography (OCT), fundus autofluorescence (FAF), OCT angiography, and ultrawide field imaging and FFA have helped clinicians in the detection of certain biomarkers that can identify disease at an early stage and predict response to treatment in diabetic macular edema. This article will summarize the role of different imaging biomarkers in characterizing diabetic retinopathy and their potential contribution in its management.

Retinopathy Phenotypes in Type 2 Diabetes with Different Risks for Macular Edema and Proliferative Retinopathy

Our group reported that three diabetic retinopathy (DR) phenotypes: A, characterized by low microaneurysm turnover (MAT < 6) and normal central retinal thickness (CRT); B, low MAT (<6) and increased CRT, and C, high MAT (≥6), present different risks for development of macular edema (DME) and proliferative retinopathy (PDR). To test these findings, 212 persons with type 2 diabetes (T2D) and mild nonproliferative retinopathy (NPDR), one eye per person, were followed for five years with annual visits. Of these, 172 completed the follow-up or developed an outcome: PDR or DME (considering both clinically significant macular edema (CSME) and center-involved macular edema (CIME)). Twenty-seven eyes (16%) developed either CSME (14), CIME (10), or PDR (4), with one eye developing both CSME and PDR. Phenotype A showed no association with development of vision-threatening complications. Seven eyes with phenotype B and three with phenotype C developed CIME. Phenotype C showed higher risk for CSME development, with 17.41 odds ratio (p = 0.010), compared with phenotypes A + B. All eyes that developed PDR were classified as phenotype C. Levels of HbA_1c and triglycerides were increased in phenotype C (p < 0.001 and p = 0.018, respectively). In conclusion, phenotype C identifies eyes at higher risk for development of CSME and PDR, whereas phenotype A identifies eyes at very low risk for vision-threatening complications.

[Unmet research and developmental needs in ophthalmology : A consensus-based road map of the European Vision Institute for 2019-2025]

PURPOSE

To define unmet needs in ophthalmology which can realistically be addressed in the next years (2019-2025) and to describe potential avenues for research to address these challenges.

METHODS

Outcomes of a consensus process within the European Vision Institute (EVI, Brussels) are outlined. Disease areas which are discussed comprise glaucoma, retinal dystrophies, diabetic retinopathy, dry eye disease, corneal diseases, cataract and refractive surgery.

RESULTS

Unmet needs in the mentioned disease areas are discussed and realistically achievable research projects outlined.

CONCLUSION

Considerable progress can be made in the field of ophthalmology and patient-relevant outcomes in the near future.

Unmet Needs in Ophthalmology: A European Vision Institute-Consensus Roadmap 2019-2025

PURPOSE

To define unmet needs in ophthalmology that can realistically be addressed in the next 5 years (2019-2025) and describe potential avenues for research to address these challenges.

METHODS

Outcomes of a consensus process within the European Vision institute (Brussels) are outlined. Disease areas that are discussed comprise glaucoma, retinal dystrophies, diabetic retinopathy, dry eye disease, corneal diseases, cataract and refractive surgery.

RESULTS

Unmet needs in the mentioned disease areas are discussed and realistically achievable research projects outlined.

CONCLUSIONS

Considerable progress can be made in the ophthalmic field and patient-relevant outcomes in the near future.

Microvascular imaging of the skin

Despite our understanding that the microvasculature plays a multifaceted role in the development and progression of various conditions, we know little about the extent of this involvement. A need exists for non-invasive, clinically meaningful imaging modalities capable of elucidating microvascular information to aid in our understanding of disease, and to aid in the diagnosis/monitoring of disease for more patient-specific care. In this review article, a number of imaging techniques are summarized that have been utilized to investigate the microvasculature of skin, along with their advantages, disadvantages and future perspectives in preclinical and clinical settings. These techniques include dermoscopy, capillaroscopy, Doppler sonography, laser Doppler flowmetry (LDF) and perfusion imaging, laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), including its Doppler and dynamic variant and the more recently developed OCT angiography (OCTA), photoacoustic imaging, and spatial frequency domain imaging (SFDI). Attention is largely, but not exclusively, placed on optical imaging modalities that use intrinsic optical signals to contrast the microvasculature. We conclude that whilst each imaging modality has been successful in filling a particular niche, there is no one, all-encompassing modality without inherent flaws. Therefore, the future of cutaneous microvascular imaging may lie in utilizing a multi-modal approach that will counter the disadvantages of individual systems to synergistically augment our imaging capabilities.

Central subfield thickness and cube average thickness as bioimaging biomarkers for ellipsoid zone disruption in diabetic retinopathy

BACKGROUND

To evaluate the association of central subfield thickness (CST) and cube average thickness (CAT) with ellipsoid zone (EZ) disruption on spectral domain optical coherence tomography (SD-OCT) in patients of diabetic retinopathy (DR).

METHODS

Cross sectional study including consecutive patients of type 2 diabetes mellitus [without DR (No DR, n = 97); non-proliferative DR (NPDR, n = 91); proliferative DR (PDR, n = 83)] and healthy controls (n = 82) was undertaken. CST and CAT values were measured using SD-OCT. Data was analyzed using Chi square test, ANOVA and multivariate analysis. Discriminant values of CST and CAT for EZ disruption were evaluated using receiver operator characteristic curve. Area under curve (AUC) was computed.

RESULTS

Mean CAT and CST values in the study subjects showed an incremental trend. Multivariate ordinal logistic regression analysis showed increase in CST (OR = 1.022, p < 0.001) and CAT (OR = 1.029, p < 0.001) as significant independent predictors of EZ disruption. Area under curve showed excellent predictive results of CST (AUC = 0. 943 ± 0.021, 95% CI, 0.902-0.984, p < 0.05) and CAT (AUC = 0.959 ± 0.012, 95% CI 0.936-0.982, p < 0.05), as bioimaging biomarkers, for EZ disruption.

CONCLUSION

Increase in CST and CAT is associated with increased odds of EZ disruption and these macular parameters serve as bioimaging biomarkers for EZ disruption in DR.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.