Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography

Retinal ganglion cell complex thickness in subjects with diabetes mellitus and uncontrolled hypertension in China

PURPOSE

To assess the interactive relationship between blood pressure status and diabetic mellitus (DM) with ganglion cell complex (GCC) thickness in elderly individuals in rural China.

METHODS

Participants aged 50 years and older in a rural area of Daxing District, Beijing, were recruited in this study from October 2018 to November 2018. All subjects underwent a comprehensive systemic and ocular examination. Blood pressure status was graded as normotension, controlled hypertension and uncontrolled hypertension according to blood pressure measurements and the use of any medication for hypertension treatment. GCC parameters were measured by spectral-domain optical coherence tomography (SD-OCT). Generalized linear models (GLM) adjusted for related potential confounders were used to assess the interaction between DM and blood pressure status.

RESULTS

Among 1415 screened subjects (2830 eyes), a total of 1117 eyes were enrolled in the final analysis. GLM analysis showed a significant interactive relationship between DM with uncontrolled hypertension status (β = 3.868, p = 0.011). GCC thickness would decrease 0.255 μm per year as the age increased (β=-0.255, p < 0.001). In a subgroup of 574 subjects with uncontrolled hypertension, DM was associated with an increased average of GCC thickness (β = 1.929, p = 0.022).

CONCLUSIONS

The present results revealed a significant interactive relationship between blood pressure status and DM. The average GCC thickness increased in individuals with DM combined with uncontrolled hypertension, which should be considered in the measurement of GCC. Further studies are warranted to explore ganglion cells changes as a non-invasive method to detect neuron alterations in individuals with DM and uncontrolled hypertension.

TRAIL REGISTRATION

The registration number of the present trial in the Chinese Clinical Trial Registry is ChiCTR2000037944.

Evaluation of thickness of individual macular retinal layers in diabetic eyes from optical coherence tomography

The effect of diabetes mellitus (DM) on individual retinal layers remains incompletely understood. We evaluated the intra-retinal layer thickness alterations in 71 DM eyes with no diabetic retinopathy (DR), 90 with mild DR, and 63 with moderate DR without macular edema, using spectral-domain optical coherence tomography (SD-OCT) and the Iowa Reference Algorithm for automated retinal layer segmentation. The average thickness of 10 intra-retinal layers was then corrected for ocular magnification using axial length measurements, and pairwise comparisons were made using multivariable linear regression models adjusted for gender and race. In DM no DR eyes, significant thinning was evident in the ganglion cell layer (GCL; p < 0.001), inner nuclear layer (INL; p = 0.001), and retinal pigment epithelium (RPE; p = 0.014) compared to normal eyes. Additionally, mild DR eyes exhibited a thinner inner plexiform layer (IPL; p = 0.008) than DM no DR eyes. Conversely, moderate DR eyes displayed thickening in the INL, outer nuclear layer, IPL, and retinal nerve fiber layer (all p ≤ 0.002), with notably worse vision. These findings highlight distinctive patterns: early diabetic eyes experience thinning in specific retinal layers, while moderate DR eyes exhibit thickening of certain layers and slightly compromised visual acuity, despite the absence of macular edema. Understanding these structural changes is crucial for comprehending diabetic eye complications.

ASSOCIATIONS BETWEEN CHOROIDAL ALTERATIONS AND EARLY NEURODEGENERATION IN DIABETES WITHOUT DIABETIC RETINOPATHY: Insights From Ultra-Widefield Optical Coherence Tomography Angiography Imaging

PURPOSE

To identify associations between choroidal alterations and the reduction of peripapillary retinal nerve fiber layer (pRNFL) thickness in diabetes without diabetic retinopathy (nondiabetic retinopathy, NDR).

METHODS

This retrospective cross-sectional study included 143 eyes from 83 patients with NDR and 124 eyes from 82 matched healthy controls. Ultra-widefield swept-source optical coherence tomography angiography was used to automatically measure retinal and choroidal thickness (ChT), retinal vascular density, and choroidal vascular metrics. Data were analyzed using Student's t-tests, generalized estimating equations, and generalized linear mixed models.

RESULTS

Patients with NDR exhibited significant reductions in perifoveal ChT (e.g., perifoveal inferior region: 253.42 ± 86.59 µm vs. 281.01 ± 80.25 µm, P = 0.026 in GEE test) compared with the controls. The NDR group showed a significant decrease in the choroidal vascular index (P = 0.012 in GEE test), and an increase in the choroidal stromal index (P = 0.012 in GEE test). The average pRNFL thickness significantly decreased in patients with NDR (114.58 ± 11.88 µm vs. 120.25 ± 16.36 µm, P = 0.005 in GEE test). The thickness of the outer nuclear layer and total retina significantly decreased in patients with NDR (P < 0.05). In multivariate models, ChT was significantly correlated with pRNFL thickness (β = 0.041, P = 0.001), even after adjusting by confounding factors (β = 0.056, P = 0.001).

CONCLUSION

In NDR, there were decreases in ChT, choroidal vascular index, pRNFL thickness, and outer nuclear layer thickness. The reduction in ChT was independently associated with the reduction in pRNFL thickness, suggesting that ChT could serve as a predictor of retinal neurodegeneration in NDR.

Advances in Structural and Functional Retinal Imaging and Biomarkers for Early Detection of Diabetic Retinopathy

Diabetic retinopathy (DR), a vision-threatening microvascular complication of diabetes mellitus (DM), is a leading cause of blindness worldwide that requires early detection and intervention. However, diagnosing DR early remains challenging due to the subtle nature of initial pathological changes. This review explores developments in multimodal imaging and functional tests for early DR detection. Where conventional color fundus photography is limited in the field of view and resolution, advanced quantitative analysis of retinal vessel traits such as retinal microvascular caliber, tortuosity, and fractal dimension (FD) can provide additional prognostic value. Optical coherence tomography (OCT) has also emerged as a reliable structural imaging tool for assessing retinal and choroidal neurodegenerative changes, which show potential as early DR biomarkers. Optical coherence tomography angiography (OCTA) enables the evaluation of vascular perfusion and the contours of the foveal avascular zone (FAZ), providing valuable insights into early retinal and choroidal vascular changes. Functional tests, including multifocal electroretinography (mfERG), visual evoked potential (VEP), multifocal pupillographic objective perimetry (mfPOP), microperimetry, and contrast sensitivity (CS), offer complementary data on early functional deficits in DR. More importantly, combining structural and functional imaging data may facilitate earlier detection of DR and targeted management strategies based on disease progression. Artificial intelligence (AI) techniques show promise for automated lesion detection, risk stratification, and biomarker discovery from various imaging data. Additionally, hematological parameters, such as neutrophil-lymphocyte ratio (NLR) and neutrophil extracellular traps (NETs), may be useful in predicting DR risk and progression. Although current methods can detect early DR, there is still a need for further research and development of reliable, cost-effective methods for large-scale screening and monitoring of individuals with DM.

Assessment of area and structural irregularity of retinal layers in diabetic retinopathy using machine learning and image processing techniques

Diabetes retinopathy prevention necessitates early detection, monitoring, and treatment. Non-invasive optical coherence tomography (OCT) shows structural changes in the retinal layer. OCT image evaluation necessitates retinal layer segmentation. The ability of our automated retinal layer segmentation to distinguish between normal, non-proliferative (NPDR), and proliferative diabetic retinopathy (PDR) was investigated in this study using quantifiable biomarkers such as retina layer smoothness index (SI) and area (S) in horizontal and vertical OCT images for each zone (fovea, superior, inferior, nasal, and temporal). This research includes 84 eyes from 57 individuals. The study shows a significant difference in the Area (S) of inner nuclear layer (INL) and outer nuclear layer (ONL) in the horizontal foveal zone across the three groups (p < 0.001). In the horizontal scan, there is a significant difference in the smoothness index (SI) of the inner plexiform layer (IPL) and the upper border of the outer plexiform layer (OPL) among three groups (p < 0.05). There is also a significant difference in the area (S) of the OPL in the foveal zone among the three groups (p = 0.003). The area (S) of the INL in the foveal region of horizontal slabs performed best for distinguishing diabetic patients (NPDR and PDR) from normal individuals, with an accuracy of 87.6%. The smoothness index (SI) of IPL in the nasal zone of horizontal foveal slabs was the most accurate at 97.2% in distinguishing PDR from NPDR. The smoothness index of the top border of the OPL in the nasal zone of horizontal slabs was 84.1% accurate in distinguishing NPDR from PDR. Smoothness index of IPL in the temporal zone of horizontal slabs was 89.8% accurate in identifying NPDR from PDR patients. In conclusion, optical coherence tomography can assess the smoothness index and irregularity of the inner and outer plexiform layers, particularly in the nasal and temporal regions of horizontal foveal slabs, to distinguish non-proliferative from proliferative diabetic retinopathy. The evolution of diabetic retinopathy throughout severity levels and its effects on retinal layer irregularity need more study.

In vivo retinal imaging is associated with cognitive decline, blood-brain barrier disruption and neuroinflammation in type 2 diabetic mice

Introduction

Type 2 diabetes (T2D) is associated with chronic inflammation and neurovascular changes that lead to functional impairment and atrophy in neural-derived tissue. A reduction in retinal thickness is an early indicator of diabetic retinopathy (DR), with progressive loss of neuroglia corresponding to DR severity. The brain undergoes similar pathophysiological events as the retina, which contribute to T2D-related cognitive decline.

Methods

This study explored the relationship between retinal thinning and cognitive decline in the LepR db/db model of T2D. Diabetic db/db and non-diabetic db/+ mice aged 14 and 28 weeks underwent cognitive testing in short and long-term memory domains and in vivo retinal imaging using optical coherence tomography (OCT), followed by plasma metabolic measures and ex vivo quantification of neuroinflammation, oxidative stress and microvascular leakage.

Results

At 28 weeks, mice exhibited retinal thinning in the ganglion cell complex and inner nuclear layer, concomitant with diabetic insulin resistance, memory deficits, increased expression of inflammation markers and cerebrovascular leakage. Interestingly, alterations in retinal thickness at both experimental timepoints were correlated with cognitive decline and elevated immune response in the brain and retina.

Discussion

These results suggest that changes in retinal thickness quantified with in vivo OCT imaging may be an indicator of diabetic cognitive dysfunction and neuroinflammation.

QUANTITATIVE OPTICAL COHERENCE TOMOGRAPHY REVEALS ROD PHOTORECEPTOR DEGENERATION in EARLY DIABETIC RETINOPATHY

PURPOSE

This study is to test the feasibility of optical coherence tomography (OCT) detection of photoreceptor abnormality and to verify that the photoreceptor abnormality is rod predominated in early diabetic retinopathy (DR).

METHODS

OCT images were acquired from normal eyes, diabetic eyes with no DR, and mild nonproliferative DR (NPDR). Quantitative features, including thickness measurements quantifying band distances and reflectance intensity features among the external limiting membrane, inner segment ellipsoid, interdigitation zone, and retinal pigment epithelium were determined. Comparative OCT analysis of central fovea, parafovea, and perifovea were implemented to verify that the photoreceptor abnormality is rod predominated in early DR.

RESULTS

Thickness abnormalities between the inner segment ellipsoid and interdigitation zone also showed a decreasing trend among cohorts. Reflectance abnormalities of the external limiting membrane, interdigitation zone, and inner segment ellipsoid were observed between healthy, no DR, and mild NPDR eyes. The normalized inner segment ellipsoid/retinal pigment epithelium intensity ratio revealed a significant decreasing trend in the perifovea, but no detectable difference in central fovea.

CONCLUSION

Quantitative OCT analysis consistently revealed outer retina, i.e., photoreceptor changes in diabetic patients with no DR and mild NPDR. Comparative analysis of central fovea, parafovea, and perifovea confirmed that the photoreceptor abnormality is rod-predominated in early DR.

Ocular delivery of sunitinib-loaded nanoparticles doped in tragacanthic acid hydrogel in treatment of diabetic retinopathy in rats

OBJECTIVE

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus. This study aimed to compare the effect of sunitinib-loaded poly (glycerol sebacate) (PGS)/gelatin nanoparticles doped in an injectable hydrogel with bevacizumab as a standard treatment of DR.

METHODS

The shear-sensitive hydrogel was prepared based on tragacanthic acid (TA) cross-linked with sodium acetate. DR was induced in rats by streptozotocin (STZ), and the animals were injected intravitreally a single dose of 20 µL sunitinib solution in three different concentrations (12.5, 25, and 50 µg/mL), sunitinib-loaded nanoparticles in hydrogel (413 μg/mL) and bevacizumab solution (6.25 mg/mL). The efficacy of the treatments was studied by histological and immunohisitological tests, angiogenesis, and optical coherence tomography (OCT). Vascular endothelial growth factor (VEGF) concentration was measured in the retina.

RESULTS

The results revealed that 20 µL of sunitinib with the concentration of 25 µg/mL was effective in DR without any disruption in the retina or any other side effects. This dose was considered the therapeutic dose for nanoparticles. Sunitinib loaded PGS/gelatine nanoparticles that were incorporated in the injectable hydrogel were as effective as bevacizumab in controlling DR. Although sunitinib solution reduced VEGF production and neovascularization in the retina compared to the negative control group, it was not as suitable as the nanoparticles. TA-based hydrogel showed no toxicity on the normal retina, and the angiography and histologic studies confirmed the VEGF results. Conclusions: Sunitinib nanoparticles doped in TA hydrogel may be an appropriate substitution of bevacizumab in the treatment of DR.

Association of inner retinal reflectivity with qualitative and quantitative changes in retinal layers over time in diabetic eyes without retinopathy

OBJECTIVE

To assess the course of neurodegeneration based on retinal layer thickness and integrity analysis in diabetic patients without retinopathy and to evaluate its association with inner retinal reflectivity.

METHODS

This retrospective case-control study included 80 eyes of 80 patients with DM without retinopathy and 40 eyes of 40 healthy subjects with a follow-up of ≥1 year. SD-OCT was used for assessment of retinal reflectivity and macular layer thicknesses. Optical intensity ratios (OIRs) were defined as the mean OCT reflectivity of ganglion cell and inner nuclear layer to the mean reflectivity of RPE.

RESULTS

After Bonferroni correction, thinning in pericentral, superior and nasal sectors in total retina, superior ganglion cell, pericentral and nasal inner plexiform, and superior inner retinal layers, as well as thickening in inferior and pericentral outer plexiform layer remained significant in the study group (p < 0.0125). Ganglion cell layer OIR significantly correlated with the changes in superior retina (r = 0.278, p = 0.013), central inner retina (r = 0.247, p = 0.027), and pericentral retinal thickness (r = 0.240, p = 0.032), and no eyes had disruption of retinal layers in the study group initially or finally.

CONCLUSION

Ganglion cell layer reflectivity significantly correlated with the amount of pericentral retinal thinning during the time course in the diabetic group, which was more prominent in the inner retinal layers.

Understanding Neurodegeneration from a Clinical and Therapeutic Perspective in Early Diabetic Retinopathy

Recent evidence indicates that neurodegeneration is a critical element of diabetic retinopathy (DR) pathogenesis. The neuronal cells’ apoptosis contributes to microvascular impairment and blood–retinal barrier breakdown. Therefore, neurodegeneration represents an early intervention target to slow and prevent the development of microvascular alterations visible on clinical examination. Multimodal imaging features and functional assessment can permit the identification of neuronal damage in a subclinical stage before the recognition of DR signs. Clinical features of neurodegeneration are crucial in identifying patients at high risk of developing a vascular impairment and, thus, serve as outcome measures to understand the efficacy of supplementation. The optimal approach for targeting neurodegeneration contemplates the use of topical compounds that possibly act on different elements of the pathogenic cascade. To date, clinical trials available on humans tested three different topical agents, including brimonidine, somatostatin, and citicoline, with promising results.

Challenges in Diabetic Macular Edema Management: An Expert Consensus Report

Purpose

This paper aimed to present daily-practice recommendations for the management of diabetic macular edema (DME) patients based on available scientific evidence and the clinical experience of the consensus panel.

Methods

A group of Spanish retina experts agreed to discuss different aspects related with the clinical management of DME patients.

Results

Panel was mainly focused on therapeutic objectives in DME management; definition terms; and role of biomarkers as prognostic and predictive factors to intravitreal treatment response. The panel recommends to start DME treatment as soon as possible in those eyes with a visual acuity less than 20/25 (always according to the retina unit capacity). Naïve patient was defined, in a strict manner, as a patient who, up to that moment, had never received any treatment. A refractory DME patient may be defined as the one who did not achieve a complete resolution of the disease, regardless of the treatment administered. Different optical coherence tomography biomarkers, such as disorganization of the retinal inner layers, hyperreflective dots, and cysts, have been identified as prognostic factors.

Conclusion

This document has sought to lay down a set of recommendations and to identify key issues that may be useful for the daily management of DME patients.

Photoreceptor cells and RPE contribute to the development of diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.

The Impact of Glycemic Control on Retinal Photoreceptor Layers and Retinal Pigment Epithelium in Patients With Type 2 Diabetes Without Diabetic Retinopathy: A Follow-Up Study

AIMS

To establish the sequential changes by glycemic control in the mean thickness, volume and reflectance of the macular photoreceptor layers (MPRLs) and retinal pigment epithelium in patients with type 2 diabetes without diabetic retinopathy.

METHODS

Thirty-one poorly controlled (HbA1c > 8.0%) patients with type 2 diabetes without diabetic retinopathy undergoing glycemic control and 39 control subjects with normal HbA1c levels (< 5.9%) underwent periodical full medical, neurological and ophthalmological examinations over 2 years. Glycemic variability was evaluated by standard deviation and coefficient of variation of monthly measured HbA1c levels and casual plasma glucose. 3D swept source-optical coherence tomography (OCT) and OCT-Explorer-generated enface thickness, volume and reflectance images for 9 subfields defined by Early Treatment Diabetic Retinopathy Study of 4 MPRLs {outer nuclear layer, ellipsoid zone, photoreceptor outer segment (PROS) and interdigitation zone} and retinal pigment epithelium were acquired every 3 months.

RESULTS

Glycemic control sequentially restored the thickness and volume at 6, 4 and 5 subfields of outer nuclear layer, ellipsoid zone and PROS, respectively. The thickness and volume of outer nuclear layer were restored related to the decrease in HbA1c and casual plasma glucose levels, but not related to glycemic variability and neurological tests. The reflectance of MPRLs and retinal pigment epithelium in patients was marginally weaker than controls, and further decreased at 6 or 15 months during glycemic control. The reduction at 6 months coincided with high HbA1c levels.

CONCLUSION

Glycemic control sequentially restored the some MPRL thickness, especially of outer nuclear layer. In contrast, high glucose during glycemic control decreased reflectance and may lead to the development of diabetic retinopathy induced by glycemic control. The repeated OCT examinations can clarify the benefit and hazard of glycemic control to the diabetic retinopathy.

Alterations of retinal thickness measured by optical coherence tomography correlate with neurophysiological measures in diabetic polyneuropathy

AIMS/INTRODUCTION

Diabetic polyneuropathy (DPN) and diabetic retinopathy (DR) are traditionally regarded as microvascular complications. However, these complications may share similar neurodegenerative pathologies. Here we evaluate the correlations in the severity of DPN and changes in the thickness of neuroretinal layers to elucidate whether these complications exist at similar stages of progression.

MATERIALS AND METHODS

A total of 43 patients with type 2 diabetes underwent a nerve conduction study (NCS), a macular optical coherence tomography, and a carotid artery ultrasound scan. Diabetic polyneuropathy was classified according to Baba's classification using NCS. The retina was automatically segmented into four layers; ganglion cell complex (GCC), inner nuclear layer/outer plexiform layer (INL/OPL), outer nuclear layer/photoreceptor inner and outer segments, and retinal pigment epithelium (RPE). The thickness of each retinal layer was separately analyzed for the fovea and the parafovea.

RESULTS

Fourteen patients were classified as having moderate to severe diabetic polyneuropathy. The thicknesses of the foveal and parafoveal INL/OPL increased in patients with diabetic polyneuropathy compared with patients without. The thickness of the parafoveal retinal pigment epithelium decreased in patients with diabetic polyneuropathy. The thinning of parafoveal ganglion cell complex and foveal and parafoveal retinal pigment epithelium were positively correlated with deterioration of nerve functions in the nerve conduction study, but the thickening of INL/OPL was positively correlated with the nerve function deterioration. The thinning of parafoveal ganglion cell complex and foveal retinal pigment epithelium were positively correlated with the thickening of the carotid intima-media.

CONCLUSIONS

Depending on the progression of diabetic polyneuropathy, the ganglion cell complex and retinal pigment epithelium became thinner and the INL/OPL became thicker. These retinal changes might be noteworthy for pathological investigations and for the assessment of diabetic polyneuropathy and diabetic retinopathy.

Mitochondrial Dysfunction as a Novel Target for Neuroprotective Nutraceuticals in Ocular Diseases

The eyes require a rich oxygen and nutrient supply; hence, the high-energy demand of the visual system makes it sensitive to oxidative stress. Excessive free radicals result in mitochondrial dysfunction and lead to retinal neurodegeneration, as an early stage of retinal metabolic disorders. Retinal cells are vulnerable because of their coordinated interaction and intricate neural networks. Nutraceuticals are believed to target multiple pathways and have shown neuroprotective benefits by scavenging free radicals and promoting mitochondrial gene expression. Furthermore, encouraging results demonstrate that nutraceuticals improve the organization of retinal cells and visual functions. This review discusses the mitochondrial impairments of retinal cells and the mechanisms underlying the neuroprotective effects of nutraceuticals. However, some unsolved problems still exist between laboratory study and clinical therapy. Poor bioavailability and bioaccessibility strongly limit their development. A new delivery system and improved formulation may offer promise for health care applications.

Spatial and spatio-temporal statistical analyses of retinal images: a review of methods and applications

Background

Clinical research and management of retinal diseases greatly depend on the interpretation of retinal images and often longitudinally collected images. Retinal images provide context for spatial data, namely the location of specific pathologies within the retina. Longitudinally collected images can show how clinical events at one point can affect the retina over time. In this review, we aimed to assess statistical approaches to spatial and spatio-temporal data in retinal images. We also review the spatio-temporal modelling approaches used in other medical image types.

Methods

We conducted a comprehensive literature review of both spatial or spatio-temporal approaches and non-spatial approaches to the statistical analysis of retinal images. The key methodological and clinical characteristics of published papers were extracted. We also investigated whether clinical variables and spatial correlation were accounted for in the analysis.

Results

Thirty-four papers that included retinal imaging data were identified for full-text information extraction. Only 11 (32.4%) papers used spatial or spatio-temporal statistical methods to analyse images, others (23 papers, 67.6%) used non-spatial methods. Twenty-eight (82.4%) papers reported images collected cross-sectionally, while 6 (17.6%) papers reported analyses on images collected longitudinally. In imaging areas outside of ophthalmology, 19 papers were identified with spatio-temporal analysis, and multiple statistical methods were recorded.

Conclusions

In future statistical analyses of retinal images, it will be beneficial to clearly define and report the spatial distributions studied, report the spatial correlations, combine imaging data with clinical variables into analysis if available, and clearly state the software or packages used.

Ganglion cell layer thickening in well-controlled patients with type 1 diabetes: an early sign for diabetic retinopathy?

PURPOSE

To evaluate early changes in retinal layers using optical coherence tomography (OCT) in patients with long-standing type 1 diabetes (DM1) receiving intensified insulin therapy.

METHODS

In a cross-sectional case-control study 150 patients with DM1 and 150 age- and sex-matched healthy control participants underwent OCT imaging. Scans of both eyes were analysed for different layers (NFL, GCL (+IPL), INL, outer layer complex (OLC, including OPL, ONL and ELM) and photoreceptors (PR)) in all subfields of an ETDRS grid. All analyses were performed semi-automatically using custom software by certified graders of the Vienna Reading Center. ANOVA models were used to compare the mean thickness of the layers between patients and controls.

RESULTS

Six hundred eyes with 512 datapoints in 49 b-scans in each OCT were analysed. Mean thickness in patients/controls was 31.35 μm/30.65 μm (NFL, p = 0.0347), 76.7 μm/73.15 μm (GCL, p ≤ 0.0001), 36.29 μm/37.13 μm (INL, p = 0.0116), 114.34 μm/112.02 μm (OLC, p < 0.0001) and 44.71 μm/44.69 μm (PR, p = 0.9401). When evaluating the ETDRS subfields separately for clinically meaningful hypotheses, a significant swelling of the GCL in patients could be found uniformly and a central swelling for the OLC, whereas the distribution of NFL and INL thickening suggests that their statistical significance was not clinically relevant.

CONCLUSION

These preliminary results demonstrate that preclinical retinal changes in patients with long-standing DM1 can be found by retinal layer evaluation. However, the changes are layer-specific, with significant thickening of the GCL and less so of the OLC suggesting a role as an early sign for diffuse swelling and the evolution of DME even in well-controlled diabetes.

En face slab optical coherence tomography imaging successfully monitors progressive degenerative changes in the innermost layer of the diabetic retina

OBJECTIVE

To evaluate the usefulness of en face slab optical coherence tomography (OCT) imaging for monitoring diabetic retinal neurodegeneration with supporting animal experimental data.

RESEARCH DESIGN AND METHODS

We retrospectively examined 72 diabetic eyes over 3 years using Cirrus-HD OCT. Two-dimensional en face slab OCT images of the innermost retina were reconstructed and graded according to the ratio of dark area to total area, and relative red, green, and blue color area ratios were calculated and used as indexes for each en face slab OCT image. Values from en face OCT images were used for statistical analyses. To obtain insight into the pathogenesis of diabetic retinal neurodegeneration, we used the InsPr-Cre;Pdk1^flox/flox diabetic mouse model.

RESULTS

Both OCT grade and relative red color area ratio significantly increased with the advancing stage of diabetic retinopathy (p=0.018 and 0.006, respectively). After a mean follow-up period of 4.6 years, the trend was unchanged in the analyses of 42 untreated eyes (p<0.001 and 0.001, respectively). Visual acuity showed a weak but significant negative correlation with the red color ratio on en face slab OCT images, but central retinal thickness did not exhibit a clinically meaningful correlation with values obtained from en face slab OCT images. Immunohistochemical analyses of InsPr-Cre;Pdk1^flox/flox diabetic mice demonstrated the loss of ganglion axon bundles and thinning of laminin without apparent retinal vascular change at the age of 20 weeks.

CONCLUSIONS

En face slab OCT imaging would be a novel useful modality for the assessment of diabetic retinal neurodegeneration as it could detect subtle optical changes occurring in the innermost retina in diabetic eyes. Our animal experimental data suggest that dark areas observed on en face slab OCT images might be the impairment of the extracellular matrix as well as neurons.

Alterations of Retinal Pigment Epithelium-Photoreceptor Complex in Patients with Type 2 Diabetes Mellitus without Diabetic Retinopathy: A Cross-Sectional Study

AIM

A cross-sectional study was performed to examine the alterations of the retinal pigment epithelium- (RPE-) photoreceptor complex layer in type 2 diabetes mellitus (DM) without diabetic retinopathy (DR), using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Patients with type 2 DM without DR and healthy controls without DM were recruited. All participants underwent examinations including SD-OCT. The thickness measurements of the retinal neural layers were calculated after automatic segmentation. An independent-sample t-test was used to compare the means of the thickness of retinal neural layers in patients with DM and healthy controls.

RESULTS

Sixty-seven eyes from 67 patients with DM and 30 eyes from 30 healthy controls were included in this study. No significant differences were found in age (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (P = 0.601), gender (.

CONCLUSION

Lesions in the RPE-photoreceptor complex are present without vascular abnormalities, which may precede the alterations of ganglion cells in patients with type 2 DM.

Automated Deformation-Based Analysis of 3D Optical Coherence Tomography in Diabetic Retinopathy

Diabetic retinopathy (DR) is a significant microvascular complication of diabetes mellitus and a leading cause of vision impairment in working age adults. Optical coherence tomography (OCT) is a routinely used clinical tool to observe retinal structural and thickness alterations in DR. Pathological changes that alter the normal anatomy of the retina, such as intraretinal edema, pose great challenges for conventional layer-based analysis of OCT images. We present an alternative approach for the automated analysis of OCT volumes in DR research based on nonlinear registration. In this paper, we first obtain an anatomically consistent volume of interest (VOI) in different OCT images via carefully designed masking and affine registration. After that, efficient B-spline transformations are computed using stochastic gradient descent optimization. Using the OCT volumes of normal controls, for which layer-based segmentation works well, we demonstrate the accuracy of our registration-based analysis in aligning layer boundaries. By nonlinearly registering the OCT volumes of DR subjects to an atlas constructed from normal controls and measuring the Jacobian determinant of the deformation, we can simultaneously visualize tissue contraction and expansion due to DR pathology. Tensor-based morphometry (TBM) can also be performed for quantitative analysis of local structural changes. In our experimental results, we apply our method to a dataset of 105 subjects and demonstrate that volumetric OCT registration and TBM analysis can successfully detect local retinal structural alterations due to DR.

Outer Retinal Structure and Function Deficits Contribute to Circadian Disruption in Patients With Type 2 Diabetes

Purpose

Light transmitted by retinal photoreceptors provides the input for circadian photoentrainment. In diabetes, there is a high prevalence of circadian and sleep disruption but the underlying causes are not well understood. Patients with diabetes can exhibit dysfunctional photoreceptors but their role in circadian health is not known. Here we quantify photoreceptor function and contributions to circadian health and sleep in patients with diabetes without diabetic retinopathy and healthy controls.

Methods

Rod, cone, and melanopsin function was derived using chromatic pupillometry in 47 participants including 23 patients with type 2 diabetes and 24 age-matched healthy controls after an ophthalmic examination including retinal thickness assessment using optical coherence tomography. Circadian health was determined using dim light melatonin onset (DLMO) and sleep questionnaires; light exposure was measured using actigraphy.

Results

Compared with the control group, the patients with diabetes had a significantly earlier DLMO (1 hour) (P = 0.008), higher subjective sleep scores (P < 0.05), a reduction in pupil constriction amplitude for red stimuli (P = 0.039) and for the early postillumination pupil response (PIPR) for blue (P = 0.024) stimuli. There were no between-group differences in the light exposure pattern, activity levels, and intrinsic melanopsin-mediated PIPR amplitude (P > 0.05). A significant correlation was evident between outer retinal thickness and DLMO (r = -0.65, P = 0.03) and the pupil constriction amplitude (r = 0.63, P = 0.03); patients with thinner retina had earlier DLMO and lower pupil amplitudes.

Conclusions

We infer that the observed changes in circadian function in patients with no diabetic retinopathy are due to structural and functional outer retinal rod photoreceptor deficits at early stage of diabetic eye disease.

New imaging systems in diabetic retinopathy

Various imaging modalities are of significant utility in the screening, grading, treatment, and follow-up of the different stages of diabetic retinopathy (DR) and diabetic macular edema. Color stereographic photography, fluorescein angiography, and optical coherence tomography (OCT) have been the gold standard for DR imaging for years. Besides these tools, newer technologies are gaining validation and popularity, such as fundus autofluorescence and OCT angiography. Furthermore, widefield retinography and ultra-widefield retinography have been introduced for a more comprehensive evaluation of the medium-far and very-far retinal peripheries, which is crucial for the assessment of the diverse manifestations of the disease. The aim of this review is to illustrate the recent advancements of the imaging systems for diagnosing DR, with a focus on the newest and noninvasive diagnostic tools.

Visualizing Structure and Vascular Interactions: Macular Nonperfusion in Three Capillary Plexuses

BACKGROUND AND OBJECTIVE

To assess the relationship between retinal vascular and structural changes in the superficial, middle, and deep capillary plexuses (SCP, MCP, DCP) using optical coherence tomography angiography (OCTA) and en face OCT.

PATIENTS AND METHODS

Patients with diabetic retinopathy were imaged using the Cirrus HD-OCT with AngioPlex. Using manual segmentation of the retinal layers, the authors compared OCTA to en face OCT images to examine corresponding patterns in each of the three capillary plexuses.

RESULTS

Areas of decreased perfusion and capillary dropout on OCTA were found to be associated with three corresponding lesions on en face OCT: hyporeflectivity, cystic edema, and hard exudates. Vascular changes in individual capillary plexuses corresponded with structural changes in their respective perfused retinal layers.

CONCLUSIONS

Using manual segmentation on OCTA, the authors provide a framework to visualize the relationship between vascular pathology on OCTA and structural changes on en face OCT within specific capillary plexuses. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e182-e190.].

Association between Visual Acuity and Retinal Layer Metrics in Diabetics with and without Macular Edema

Purpose

Diabetes is known to cause alterations in retinal microvasculature and tissue that progressively lead to visual impairment. Optical coherence tomography (OCT) is useful for assessment of total retinal thickening due to diabetic macular edema (DME). In the current study, we determined associations between visual acuity (VA) and retinal layer thickness, reflectance, and interface disruption derived from enface OCT images in subjects with and without DME.

Materials and Methods

Best corrected VA was measured and high-density OCT volume scans were acquired in 149 diabetic subjects. A previously established image segmentation method identified retinal layer interfaces and locations of visually indiscernible (disrupted) interfaces. Enface thickness maps and reflectance images of the nerve fiber layer (NFL), combined ganglion cell and inner plexiform layer (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE) were generated in the central macular subfield. The associations among VA and retinal layer metrics were determined by multivariate linear regressions after adjusting for covariates (age, sex, race, HbA1c, diabetes type, and duration) and correcting for multiple comparisons.

Results

In DME subjects, increased GCLIPL and OPL thickness and decreased OSL thickness were associated with reduced VA. Furthermore, increased NFL reflectance and decreased OSL reflectance were associated with reduced VA. Additionally, increased areas of INL and ONL interface disruptions were associated with reduced VA. In subjects without DME, increased INL thickness was associated with reduced VA, whereas in subjects without DME but with previous antivascular endothelium growth factor treatment, thickening of OPL was associated with reduced VA.

Conclusions

Alterations in retinal layer thickness and reflectance metrics derived from enface OCT images were associated with reduced VA with and without presence of DME, suggestive of their potential for monitoring development, progression, and treatment of DME.

[Structural endpoints for glaucoma studies]

BACKGROUND

Structural endpoints have been discussed as surrogate endpoints for the approval of neuroprotective drugs in glaucoma.

OBJECTIVE

Is the evidence strong enough to establish structural endpoints as surrogate endpoints?

MATERIAL AND METHODS

Review of current understanding between structure and function in glaucoma.

RESULTS

The introduction of optical coherence tomography has revolutionized imaging in glaucoma patients. Clinically either the nerve fiber layer thickness can be measured along a circle centered in the optic nerve head or the ganglion cell layer thickness can be assessed in the macular region, the latter being quantified in combination with other inner retinal layers. On a microscopic level there is a strong correlation between structural and functional loss but this relation can only partially be described with currently available clinical methods. This is particularly true for longitudinal course of the disease in glaucoma patients. Novel imaging techniques that are not yet used clinically may have the potential to increase our understanding between structure and function in glaucoma but further research in this field is required.

CONCLUSION

The current evidence does not allow the establishment of structural endpoints as surrogate endpoints for phase 3 studies in glaucoma. Neuroprotective drugs have to be approved on the basis of visual field data because this is the patient-relevant endpoint. Structural endpoints can, however, play an important role in phase 2 and proof of concept studies.

Effects of the neuroprotective drugs somatostatin and brimonidine on retinal cell models of diabetic retinopathy

AIMS

Diabetic retinopathy is considered a microvascular disease, but recent evidence has underlined early involvement of the neuroretina with interactions between microvascular and neural alterations. Topical administration of somatostatin (SST), a neuroprotective molecule with antiangiogenic properties, prevents diabetes-induced retinal neurodegeneration in animals. The α₂-adrenergic receptor agonist brimonidine (BRM) decreases vitreoretinal vascular endothelial growth factor and inhibits blood-retinal barrier breakdown in diabetic rats. However, SST and BRM effects on microvascular cells have not yet been studied. We investigated the behaviour of these drugs on the crosstalk between microvasculature and neuroretina.

METHODS

Expression of SST receptors 1-5 in human retinal pericytes (HRP) was checked. We subsequently evaluated the effects of diabetic-like conditions (high glucose and/or hypoxia) with/without SST/BRM on HRP survival. Endothelial cells (EC) and photoreceptors were maintained in the above conditions and their conditioned media (CM) used to culture HRP. Vice versa, HRP-CM was used on EC and photoreceptors. Survival parameters were assessed.

RESULTS

HRP express the SST receptor 1 (SSTR1). Glucose fluctuations mimicking those occurring in diabetic subjects are more damaging for pericytes and photoreceptors than stable high glucose and hypoxic conditions. SST/BRM added to HRP in diabetic-like conditions decrease EC apoptosis. However, neither SST nor BRM changed the response of pericytes and neuroretina-vascular crosstalk under diabetic-like conditions.

CONCLUSIONS

Retinal pericytes express SSTR1, indicating that they can be a target for SST. Exposure to SST/BRM had no adverse effects, direct or mediated by the neuroretina, suggesting that these molecules could be safely evaluated for the treatment of ocular diseases.