Increased serum levels of urea and creatinine are surrogate markers for disruption of retinal photoreceptor external limiting membrane and inner segment ellipsoid zone in type 2 diabetes mellitus. Retina. 2017;37:344-349. [PMID: 28118284 DOI: 10.1097/iae.0000000000001163]

The Ellipsoid Zone Is a Structural Biomarker for Visual Outcomes in Diabetic Macular Edema and Macular Hole Management

OBJECTIVES

The goal was to study the ellipsoid zone (EZ) as a structural biomarker for final visual outcomes after pharmacological intervention in center-involving diabetic macular edema (DME) and surgical intervention for full-thickness macular holes (FTMHs).

METHODS

This was a tertiary care center-based retrospective study. After sample size calculations, data from 64 consecutive cases were collected, with subjects aged between 40 and 60 years. Thirty-two cases of DME with anti-vascular endothelial growth factor (VEGF) therapy and 32 cases of FTMHs with successful macular hole surgery (MHS) were studied. Spectral-domain optical coherence tomography (SD-OCT) data were collected. Measurements of EZ defects documented at the time of presentation and 12 weeks after intervention were analyzed using the caliper function of the machine. EZ restoration was graded, and a Pearson correlation analysis was performed.

RESULTS

Mean logMAR VA decreased after intravitreal therapy (IVT) from 1.12 ± 0.22 pre-intervention to 0.81 ± 0.41 post-intervention and after MHS, from 1.05 + 0.25 to 0.62 + 0.11 (p < 0.001). EZ disruption reduced from 73.4% to 19.4% after IVT and from 67% to 19.3% after MHS. DME and MHS postoperative visual acuity and residual EZ defect were observed to have a statistically significant linear correlation (r = 0.794, p < 0.001 and r = 0.894, p < 0.001, respectively). The EZ was found to be an excellent structural biomarker for final BCVA (area under curve = 0.95 for DME and 1.00 for MHS).

CONCLUSION

Notable EZ restoration results were obtained from pharmacological and surgical interventions. The EZ proves to be a critical structural biomarker for predicting visual outcomes in center-involving DME and MHS.

Retinal photoreceptor ellipsoid zone is a structural biomarker for visual outcome after successful macular hole surgery: A novel grading system-based study

PURPOSE

To develop a novel external limiting membrane (ELM) and ellipsoid zone (EZ) restoration-based grading system after successful macular hole surgery (MHS) and to evaluate EZ as a structural biomarker for the final visual outcome.

METHODS

In a tertiary care center-based retrospective study, 34 consecutive cases of successful MHS for full-thickness macular holes (FTMHs) were included. Spectral domain optical coherence tomography (SD-OCT) cross-sectional analysis was performed on preoperative and postoperative data of weeks 1, 4, 12, and 24, respectively. Sequential measurements of FTMH size, ELM and EZ defect were performed using the caliper function of SD-OCT. MHS was uniquely graded as grade 0: persistence of ELM and EZ defect; grade 1: partial or complete restoration of ELM with shortening of EZ defect; and grade 2: complete restoration of ELM and EZ. Data were statistically analyzed on Statistical Package for the Social Sciences software-version 24.

RESULTS

MHS was graded as grade 0 ( n = 8), grade 1 ( n = 15), and grade 2 ( n = 11). Best corrected visual activity (BCVA) was found to be 1.13 ± 0.19 in grade 0, 0.59 ± 0.09 in grade 1, and 0.26 ± 0.06 in grade 2. One-way analysis of variance showed improvement in final BCVA among the three grades ( P < 0.001) Postoperative visual acuity and residual EZ defect had a statistically significant linear correlation ( r = 0.899, P < 0.001). EZ was found to be an excellent structural biomarker for final BCVA (area under the curve = 0.99).

CONCLUSION

Successful MHS is associated with better visual outcomes in eyes with restored EZ. ELM restoration preceded EZ regeneration. MHS novel grading system is physician friendly, incorporates pathoanatomic aspects, and correlates well with visual outcomes.

Prevalence and assessment of diabetic retinopathy in a densely populated suburban area of Tianjin, China - The Beichen Eye Study

PURPOSE

The aim of this study is to explore the prevalence, associated risk factors, and the influence of urbanization on the epidemiology of diabetic retinopathy (DR) and diabetic macular edema (DME).

METHODS

This study utilized a cross-sectional design to survey residents aged 50 and older in the Beichen community, Tianjin. Participants underwent thorough examinations, including questionnaire surveys, laboratory blood tests, eye assessments, fundus photography, and optical coherence tomography (OCT) scans. DR was diagnosed using the retinopathy severity scale from fundus photographs based on the Early Treatment Diabetic Retinopathy Study (ETDRS) classification system. DME was identified through medical history records and OCT evaluations. In this study, we analyzed and assessed the prevalence and risk factors associated with DR and DME.

RESULTS

The study included 5,648 participants, and 1,182 of these were diagnosed with diabetes. Among the diabetic individuals, the prevalence of DR was 28.8%. Among the eyes of those diagnosed with DR, 37.12% had mild non-proliferative DR (NPDR), 54.81% had moderate NPDR, 6.35% (33 eyes) showed severe NPDR, and 1.73% had proliferative DR (PDR). The prevalence of DME among diabetic patients was 14.13%. Age was negatively correlated with DR (OR, 0.924), while blood glucose levels (OR, 1.123) and the duration of diabetes (OR, 1.090) were positively correlated. Additionally, blood glucose levels (OR, 1.121) and the duration of diabetes (OR, 1.070) were positively associated with DME.

CONCLUSION

In this study, the prevalence of DR and DME was high in the Beichen District of Tianjin than in other parts of China. Maintaining effective glycemic control is the most important modifiable factor in reducing the risk of DR and DME progression and minimizing the risk of vision loss.

Serum urea concentration and risk of 16 site-specific cancers, overall cancer, and cancer mortality in individuals with metabolic syndrome: a cohort study

BACKGROUND

The relationship between serum urea concentration and cancer in patients with metabolic syndrome (MetS) remains unclear. This study aimed to investigate the association between serum urea concentration and 16 site-specific cancers, overall cancer incidence, and cancer mortality in individuals with MetS.

METHODS

We analysed the data of 108,284 individuals with MetS obtained from the UK Biobank. The Cox proportional hazards model was used to determine the association between serum urea concentration at recruitment and cancer. The Benjamini-Hochberg correction was used to account for multiple comparisons.

RESULTS

Over the median follow-up period of 11.86 years, 18,548 new incident cases of cancer were documented. There were inverse associations of urea concentration with overall cancer incidence, and the incidence of oesophageal and lung cancers, with respective hazard ratios (95% confidence intervals) [HR (95% CI)] for the highest (Q4) vs lowest (Q1) urea quartiles of 0.95 (0.91-0.99), 0.68 (0.50-0.92), and 0.76 (0.64-0.90). However, high serum urea concentrations increased the male prostate cancer risk (HR 1.15; 95% CI 1.02-1.30). Although the Cox model indicated a protective effect of higher urea levels against stomach (HR 0.67; 95% CI 0.45-0.98; p = 0.040; FDR 0.120) and colorectal cancer (HR 0.86; 95% CI 0.74-0.99; p = 0.048; FDR 0.123), no strong evidence of association was found after applying the Benjamin-Hochberg correction. Moreover, across the median follow-up period of 13.77 years for cancer mortality outcome, 5034 cancer deaths were detected. An "L-shaped" nonlinear dose-response relationship between urea concentration and cancer mortality was discovered (p-nonlinear < 0.001), and the HR (95% CI) for urea concentration Q4 vs Q1 was 0.83 (0.77-0.91).

CONCLUSIONS

Serum urea concentration can be considered as a valuable biomarker for evaluating cancer risk in individuals with MetS, potentially contributing to personalised cancer screening and management strategies.

Association between serum urea concentrations and the risk of colorectal cancer, particularly in individuals with type 2 diabetes: A cohort study

Dysregulation of the urea cycle (UC) has been detected in colorectal cancer (CRC). However, the impact of the UC's end product, urea, on CRC development remains unclear. We investigated the association between serum urea and CRC risk based on the data of 348 872 participants cancer-free at recruitment from the UK Biobank. Multivariable Cox proportional hazards models were fitted to conduct risk estimates. Stratification analyses based on sex, diet pattern, metabolic factors (including body mass index [BMI], the estimated glomerular filtration rate [eGFR] and type 2 diabetes [T2D]) and genetic profiles (the polygenic risk score [PRS] of CRC) were conducted to find potential modifiers. During an average of 9.0 years of follow-up, we identified 3408 (1.0%) CRC incident cases. Serum urea showed a nonlinear relationship with CRC risk (P-nonlinear: .035). Lower serum urea levels were associated with a higher CRC risk, with a fully-adjusted hazard ratio (HR) of 1.26 (95% confidence interval [CI]: 1.13-1.41) in the first quartile (Q1) of urea, compared to the Q4. This association was largely consistent across subgroups of sex, protein diet, BMI, eGFR and CRC-PRSs (P-interaction >.05); however, it was stronger in the T2D, with an interaction between urea and T2D on both additive (synergy index: 3.32, [95% CI: 1.24-8.88]) and multiplicative scales (P-interaction: .019). Lower serum urea concentrations were associated with an increased risk of CRC, with a more pronounced effect observed in individuals with T2D. Maintaining stable levels of serum urea has important implications for CRC prevention, particularly in individuals with T2D.

Central and peripheral changes in the retina and choroid in patients with diabetes mellitus without clinical diabetic retinopathy assessed by ultra-wide-field optical coherence tomography angiography

Background

To explore the central and peripheral retinal and choroidal changes in diabetic patients without clinical diabetic retinopathy (DM-NoDR) using ultra-wide-field swept-source optical coherence tomography angiography (UWF-SS-OCTA).

Methods

67 DM-NoDR eyes and 32 age-matched healthy eyes were recruited. Retinal and choroidal parameters, including qualitative retinal microangiopathy, vessel flow (VFD) and linear density (VLD), thickness, and volume, were measured in the central and peripheral areas of the 24 × 20 mm² UWF-SS-OCTA images.

Results

DM-NoDR eyes had significantly more nonperfusion area and capillary tortuosity than controls in the central and peripheral areas (p < 0.05). The presence of central capillary tortuosity was associated with higher levels of serum creatinine (OR 1.049, 95%CI 1.001-1.098; p = 0.044) and blood urea nitrogen (OR 1.775, 95%CI 1.051-2.998; p = 0.032) in DM-NoDR eyes. For DM-NoDR eyes versus controls, VFD in the 300-μm annulus around the foveal avascular zone, superficial capillary plexus (SCP), and full retina, and SCP-VLD significantly decreased, while VFD in the deep capillary plexus (DCP), retinal thickness, and retinal volume increased (p < 0.05). Analysis in the central and peripheral areas recapitulated all these findings, except for decreased peripheral thickness and volume and no difference in peripheral DCP-VFD. In DM-NoDR eyes, choriocapillaris-VFD, choroidal thickness, and choroidal volume increased in the central area, while VFD in the large and medium choroidal vessel layer decreased in the whole image (p < 0.05).

Conclusion

Retinal and choroidal changes already existed in the central and/or peripheral areas of DM-NoDR eyes. UWF-SS-OCTA, enabling the visualization of the peripheral fundus area, is a promising image technique for the early detection of fundus changes in DM-NoDR patients.

Vision-Related Quality of Life and Treatment Satisfaction Following Panretinal Photocoagulation in Diabetic Retinopathy-A Panel Study

Background and Objectives: The aim of the study was to evaluate vision-related quality of life (VR-QOL) and treatment satisfaction (TS) in patients with diabetic retinopathy treated with panretinal photocoagulation (PRP). Material and Methods: The panel study included 95 patients who underwent PRP for diabetic retinopathy. Eligible patients with no history of previous PRP were interviewer-administered the National Eye Institute Visual Function Questionnaire (NEI VFQ-25) and Retinopathy Treatment Satisfaction Questionnaire (RetTSQ) beforehandand one month after the last session of laser application. The study was conducted between June 2017 and June 2019 at tertiary care center in Serbia, Belgrade. We assessed pre- to post-PRP values of the composite score and subscale scores of VFQ-25 and RetTSQ, using a paired samples t-test. Univariate logistic regression was used to analyze the relationship between binary outcomes and potential predictors. Multivariate regression included predictors from univariate analyses that were statistically significant. Results: The mean VFQ-25 composite score was 65.4 ± 17.4 before and 63.3 ± 19.5 after PRP (p = 0.045). Subscale analysis showed that two of the 11 items achieved a significant decrease after laser application (general vision and dependency). The mean RetTSQ score at baseline was 60.0 ± 11.8 and at the exit visit was 60.3 ± 12.3 (p = 0.858). Sub-scale analysis showed significant deterioration for five of the 13 items. Multivariate logistic regression found that significant predictor of VFQ-25 composite score reduction was fewer laser burns (p = 0.002) while significant predictor of RetTSQ total score reduction was presence of hyperlipidaemia (p = 0.021). Conclusion: The use of vision-related quality of life and treatment satisfaction questionnaires in conjunction with clinical examination, appears to provide a more comprehensive overview of an individual's daily well-being following PRP. Laser treatment for diabetic retinopathy leads to deterioration of some of the patients' perceived VR-QOL and TS. Health-care providers should inform patients about their treatment options and together decide which therapeutic method is best for them.

Arginase: Biological and Therapeutic Implications in Diabetes Mellitus and Its Complications

Arginase is a ubiquitous enzyme in the urea cycle (UC) that hydrolyzes L-arginine to urea and L-ornithine. Two mammalian arginase isoforms, arginase1 (ARG1) and arginase2 (ARG2), play a vital role in the regulation of β-cell functions, insulin resistance (IR), and vascular complications via modulating L-arginine metabolism, nitric oxide (NO) production, and inflammatory responses as well as oxidative stress. Basic and clinical studies reveal that abnormal alterations of arginase expression and activity are strongly associated with the onset and development of diabetes mellitus (DM) and its complications. As a result, targeting arginase may be a novel and promising approach for DM treatment. An increasing number of arginase inhibitors, including chemical and natural inhibitors, have been developed and shown to protect against the development of DM and its complications. In this review, we discuss the fundamental features of arginase. Next, the regulatory roles and underlying mechanisms of arginase in the pathogenesis and progression of DM and its complications are explored. Furthermore, we review the development and discuss the challenges of arginase inhibitors in treating DM and its related pathologies.

Diabetic Macular Edema: Current Understanding, Molecular Mechanisms and Therapeutic Implications

Diabetic retinopathy (DR), with increasing incidence, is the major cause of vision loss and blindness worldwide in working-age adults. Diabetic macular edema (DME) remains the main cause of vision impairment in diabetic patients, with its pathogenesis still not completely elucidated. Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of DR and DME. Currently, intravitreal injection of anti-VEGF agents remains as the first-line therapy in DME treatment due to the superior anatomic and functional outcomes. However, some patients do not respond satisfactorily to anti-VEGF injections. More than 30% patients still exist with persistent DME even after regular intravitreal injection for at least 4 injections within 24 weeks, suggesting other pathogenic factors, beyond VEGF, might contribute to the pathogenesis of DME. Recent advances showed nearly all the retinal cells are involved in DR and DME, including breakdown of blood-retinal barrier (BRB), drainage dysfunction of Müller glia and retinal pigment epithelium (RPE), involvement of inflammation, oxidative stress, and neurodegeneration, all complicating the pathogenesis of DME. The profound understanding of the changes in proteomics and metabolomics helps improve the elucidation of the pathogenesis of DR and DME and leads to the identification of novel targets, biomarkers and potential therapeutic strategies for DME treatment. The present review aimed to summarize the current understanding of DME, the involved molecular mechanisms, and the changes in proteomics and metabolomics, thus to propose the potential therapeutic recommendations for personalized treatment of DME.

Automatic quantification of retinal photoreceptor integrity to predict persistent disease activity in neovascular age-related macular degeneration using deep learning

Purpose

Using deep learning (DL)-based technique, we identify risk factors and create a prediction model for refractory neovascular age-related macular degeneration (nAMD) characterized by persistent disease activity (PDA) in spectral domain optical coherence tomography (SD-OCT) images.

Materials and methods

A total of 671 typical B-scans were collected from 186 eyes of 186 patients with nAMD. Spectral domain optical coherence tomography images were analyzed using a classification convolutional neural network (CNN) and a fully convolutional network (FCN) algorithm to extract six features involved in nAMD, including ellipsoid zone (EZ), external limiting membrane (ELM), intraretinal fluid (IRF), subretinal fluid (SRF), pigment epithelium detachment (PED), and subretinal hyperreflective material (SHRM). Random forest models were probed to predict 1-year disease activity (stable, PDA, and cured) based on the quantitative features computed from automated segmentation and evaluated with cross-validation.

Results

The algorithm to segment six SD-OCT features achieved the mean accuracy of 0.930 (95% CI: 0.916–0.943), dice coefficients of 0.873 (95% CI: 0.847–0.899), a sensitivity of 0.873 (95% CI: 0.844–0.910), and a specificity of 0.922 (95% CI: 0.905–0.940). The six-metric model including EZ and ELM achieved the optimal performance to predict 1-year disease activity, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.980, the accuracy of 0.930, the sensitivity of 0.920, and the specificity of 0.962. The integrity of EZ and ELM significantly improved the performance of the six-metric model than that of the four-metric model.

Conclusion

The prediction model reveals the potential to predict PDA in nAMD eyes. The integrity of EZ and ELM constituted the strongest predictive factor for PDA in nAMD eyes in real-world clinical practice. The results of this study are a significant step toward image-guided prediction of long-term disease activity in the management of nAMD and highlight the importance of the automatic identification of photoreceptor layers.

Interleaved Optical Coherence Tomography: Clinical and Laboratory Biomarkers in Patients with Diabetic Macular Edema

(1) Background: The global burden of diabetes mellitus (DM) has been estimated to reach 600 million patients worldwide by 2040. Approximately 200 million people will develop diabetic retinopathy within this time frame. Diabetic macular edema (DME) is a severe, vision-threatening complication that can develop at any stage of diabetic retinopathy, and it represents the main cause of vision loss in patients with DM. Its harmful consequences on visual function could be prevented with timely recognition and treatment. (2) Methods: This study assessed the clinical (demographic characteristics, diabetic evolution, and systemic vascular complications); laboratory (glycated hemoglobin, metabolic parameters, capillary oxygen saturation, and renal function); ophthalmologic exam; and spectral-domain optical coherence tomography (SD–OCT) (macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, temporal inner, inferior outer, superior outer, nasal outer, and temporal outer thicknesses, disruption of the ellipsoid zone, and disruption of the inner retinal layers (DRIL) parameters in three groups of individuals: healthy controls (HC), patients with DME and type 1 DM (T1DM—group A), and patients with DME and type 2 DM (T2DM—group B) to identify novel correlations between them that would open a path to new pathogenetic hypotheses and, implicitly, to the identification of new therapeutic methods, as part of a tailored treatment within the concept of precision medicine. (3) Results: The duration of DM was significantly longer in group A as compared with group B, as were the prevalence of smoking and systemic vascular complications. Capillary oxygen saturation and estimated glomerular filtration rates were significantly lower, and serum creatinine levels were significantly higher in group A as compared to group B. Regarding the OCT findings, DME had a predominantly eccentric pattern, and the right eye was more severely affected in both groups of patients. Significantly higher values were obtained in group B as compared to group A for the following OCT biomarkers: macular volume, central macular thickness, maximal central thickness, minimal central thickness, foveal thickness, superior inner, inferior inner, nasal inner, inferior outer and nasal outer thickness. The disruption of the ellipsoid zone was significantly more prevalent within group A, whereas the overall disruption of the retinal inner layers (DRIL) was identified significantly more frequently in group B. (4) Conclusions: Whereas systemic and laboratory biomarkers were more severely affected in patients with DME and T1DM, the OCT quantitative biomarkers revealed significantly higher values in patients with DME and T2DM.

SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY BIOMARKERS OF RETINAL HYPERPERMEABILITY AND CHOROIDAL INFLAMMATION AS PREDICTORS OF SHORT-TERM FUNCTIONAL AND ANATOMICAL OUTCOMES IN EYES WITH DIABETIC MACULAR EDEMA TREATED WITH INTRAVITREAL BEVACIZUMAB

PURPOSE

To assess spectral domain optical coherence tomography biomarkers of short-term outcomes in eyes with diabetic macular edema treated with intravitreal bevacizumab.

METHODS

In a prospective interventional case series, 66 eyes with diabetic macular edema underwent 3 monthly intravitreal bevacizumab injections. Best-corrected visual acuity measurement and spectral domain optical coherence tomography were performed at baseline and at 3 months. Multivariate regression analysis was performed to investigate the baseline spectral domain optical coherence tomography parameters as predictors of functional and anatomical outcomes.

RESULTS

Patients with diabetic nephropathy had greater subfoveal choroidal thickness (300.8 ± 35.54 vs. 253.0 ± 50.07 µm, P < 0.01) and were more likely to have subretinal fluid (r = 0.26, P = 0.03) at baseline. Multivariate analysis showed that the extent of external limiting membrane disruption (P = 0.03) and the extent of disorganization of retinal inner layers (P = 0.03) at baseline were predictors of best-corrected visual acuity at 3 months, whereas the extent of disorganization of retinal inner layers (P = 0.04) and duration of diabetes mellitus (P = 0.03) were predictors of central subfield thickness at 3 months.

CONCLUSION

External limiting membrane disruption and disorganization of retinal inner layers, as the spectral domain optical coherence tomography biomarkers of retinal hyperpermeability, can predict short-term outcomes in diabetic macular edema eyes treated with intravitreal bevacizumab.

External Limiting Membrane, Photoreceptor Ellipsoid Zone Disruption, and Retinal Pigment Epithelium Alterations in Diabetic Retinopathy

Objective Diabetic retinopathy (DR), a microvascular complication of diabetes, is a leading cause of preventable blindness. Spectral domain optical coherence tomography (SD-OCT) provides cross-sectional and topographical imaging of the retina. SD-OCT resolves outer retinal layers into three hyperreflective bands—external limiting membrane (ELM), ellipsoid zone (EZ), and retinal pigment epithelium (RPE). In this article, we have studied the role of these outer retinal layers in structural and molecular changes taking place in DR.

Materials and Methods Articles with clinical features, pathogenesis, diagnosis, and treatment of DR were thoroughly studied. Articles were searched on PubMed, MEDLINE, and Cochrane Library from 2000 to 2020. Studies focusing on the role of ELM, EZ, and RPE in pathogenesis of DR based on SD-OCT were included.

Results The long-standing hyperglycemia leads to protein glycosylation resulting in formation of advanced glycation end products (AGEs). AGEs have an impact through their effect on retinal microvasculature, vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1, nitrosative and oxidative stress, and vitamin D and calcium metabolism. All these factors have been linked with disruption of outer retinal layers. AGEs lead to vascular endothelial dysfunction and release of proangiogenic factors by increasing the expression of VEGF in retinal pericytes and RPE cells. This leads to leakage and fluid accumulation resulting in diabetic macular edema (DME). In DME, there is sequential disruption of ELM and EZ and decrease in visual acuity (VA). The RPE alterations have been reported to be associated with the severity of DR and decrease in VA. Anti-VEGF therapy, most common treatment of DME, leads to restoration of barrier effect of ELM, it was found to be restored first followed by EZ restoration. Newer anti-AGEs agents and their receptor blockers are being developed which have a positive effect on maintaining the health of RPE.

Conclusion A complex molecular association exists between the structural changes in ELM, EZ, and RPE in DR. SD-OCT is an indispensable tool to study these changes as integrity of these outer layers of retina is essential for maintaining visual function of retina in DR.

External limiting membrane and ellipsoid zone structural integrity in diabetic macular edema

The external limiting membrane (ELM) and ellipsoid zone (EZ) can be observed exquisitely by SD-OCT. In diabetic macular edema (DME), dysfunction of mitochondria, represented by the EZ in the foveal photoreceptors results in reduced visual acuity (VA). An increase in VEGF was found to correlate with increased severity of DR, increased central subfield thickness (CST), and sequential disruption of ELM and EZ. The mechanism of ELM and EZ restoration after anti-VEGF therapy in DME has been discovered. The ELM restores first followed by EZ restoration. Thus, authors have discovered and established ELM as a novel retinal structural barrier.

Malfunction of outer retinal barrier and choroid in the occurrence and progression of diabetic macular edema

Diabetic macular edema (DME) is the most common cause of vision loss in diabetic retinopathy, affecting 1 in 15 patients with diabetes mellitus (DM). The disruption of the inner blood-retina barrier (BRB) has been largely investigated and attributed the primary role in the pathogenesis and progression in DME, but there is increasing evidence regarding the role of outer BRB, separating the RPE from the underlying choriocapillaris, in the occurrence and evolution of DME. The development of novel imaging technologies has led to major improvement in the field of in vivo structural analysis of the macula allowing us to delve deeper into the pathogenesis of DME and expanding our vision regarding this condition. In this review we gathered the results of studies that investigated specific outer BRB optical coherence tomography parameters in patients with DM with the aim to outline the current status of its role in the pathogenesis and progression of DME and identify new research pathways contributing to the advancement of knowledge in the understanding of this condition.

External limiting membrane: retinal structural barrier in diabetic macular edema

Advances in spectral-domain optical coherence tomography (SD-OCT) technology have enhanced the understanding of external limiting membrane (ELM) and ellipsoid zone (EZ) in diabetic macular edema. An increase in VEGF has been demonstrated to be associated with sequential ELM and EZ disruption on SD-OCT. An intact ELM is a prerequisite for an intact EZ in DME. Anti-VEGF therapy leads to restoration of barrier effect of ELM. The ELM restores first followed by EZ restoration.

Ellipsoid zone optical intensity reduction as an early biomarker for retinitis pigmentosa

PURPOSE

To investigate photoreceptor degeneration in retinitis pigmentosa (RP) by quantitatively analysing optical intensity of ellipsoid zone (EZ) on optical coherence tomography (OCT).

METHODS

We conducted OCT line scans of the horizontal meridian in 24 eyes of 24 RP patients and 30 eyes of 30 healthy controls and obtained longitudinal reflectance profiles using ImageJ at every 5 pixels. Relative optical intensity was calculated from dividing the peak of EZ by the mean of the whole retina.

RESULTS

The optical intensity of EZ variation followed a similar pattern in all patients. It decreased with eccentricity and then vanished, regardless whether it was normal or reduced at the fovea. The mean relative optical intensity of EZ in RP patients was 0.69 ± 0.13 to that of control subjects at the location just before it disappeared. The relative optical intensity of EZ at fovea was significantly correlated with the best-corrected visual acuity in patients (r = -0.617, p = 0.001).

CONCLUSION

The optical intensity of EZ detected by OCT can serve as a biomarker for early detection of photoreceptor degeneration in RP.

Dilated retinal large vessels and capillaries associated with diabetic macular edema and photoreceptor loss respectively

PURPOSE

Previously, we measured retinal large vessels and capillaries separately on optical coherence tomography angiography (OCTA). In the present study, we aim to evaluate the role of these parameters in association to diabetic macular edema (DME) and ellipsoid zone disruption (EZD).

METHODS

In this cross-sectional study, 54 eyes from 31 patients (10 females, 31 Asians) with severe non-proliferative diabetic retinopathy (25 eyes) or proliferative diabetic retinopathy (PDR, 29 eyes) were enrolled. All eyes underwent 3 × 3 mm OCTA scans centered on the fovea. Perfusion density (PD), vessel length density (VLD), and vessel diameter index (VDI) were calculated for retinal large vessels and superficial capillaries separately. Other OCTA findings included suspended scattering particles in motion (SSPiM), number of microaneurysms (MA) in all retinal layers, and the area of foveal avascular zone (FAZ) of superficial capillary plexus. DME and EZD were evaluated on B-scans. Both univariate and multivariate analysis were performed.

RESULTS

Of the 54 study eyes, 31 (57%) had DME and 21 (40%) had EZD. Multivariate regression model showed that PDR (β = 27.8, 95% confidence interval (CI): 2.7-282.8, p = 0.005), more MA (β = 2.5, 95% CI: 1.3-4.5, p = 0.003), and increased VDI of larger vessels (β = 1.9, 95% CI: 1.0-3.5, p = 0.047) were risk factors for DME. As for EZD, presence of SSPiM (β = 5.5, 95% CI: 1.2-26.1, p = 0.032) and increased VDI of capillaries (β = 3.9, 95% CI: 1.1-13.8, p = 0.034) were risk factors.

CONCLUSIONS

In eyes with diabetic retinopathy, dilation of retinal larger vessels was associated with macular edema, while dilation of retinal capillaries was associated with ellipsoid zone disruption.

Sequential restoration of external limiting membrane and ellipsoid zone after intravitreal anti-VEGF therapy in diabetic macular oedema

BACKGROUND/OBJECTIVES

To study the mechanism of restoration of retinal photoreceptor ellipsoid zone (EZ), after intravitreal bevacizumab (IVB) therapy, in diabetic macular oedema (DMO).

SUBJECTS/METHODS

Forty-four consecutive patients aged 40-65 years having type 2 diabetes mellitus (DM) with DMO were prospectively recruited for IVB therapy. It comprised of three doses (1.25 mg in 0.05 ml) of IVB at monthly intervals. Patients with other ocular and systemic diseases affecting retinal vessels and earlier ophthalmological interventions were excluded. Visual acuity (logMAR VA) was recorded. Spectral domain optical coherence tomography (SD-OCT) was performed pre and post intervention. Central sub-foveal thickness (CST) and grades of disorganization of retinal inner layers (DRIL), external limiting membrane (ELM) and EZ were assessed. Data were statistically analysed on SPSS software. Clinical trials registry: CTRI/2019/03/018135.

RESULTS

Mean logMAR VA decreased after IVB therapy from 1.78 ± 0.07 pre-intervention to 0.42 ± 0.05 post intervention (p < 0.001). Similarly, CST reduced from 354.23 ± 15.0 µm pre-intervention to 233.18 ± 7.88 µm post intervention (p < 0.001). Among qualitative variables, DRIL decreased from 93.2% pre-intervention to 13.6% post intervention. Likewise, global ELM disruption reduced from 81.8 to 9.1% and global EZ disruption reduced from 79.5 to 11.4%. ELM restoration preceded EZ restoration.

CONCLUSION

Anti-VEGF therapy restores the barrier effect of ELM. It causes ELM to restore first followed by EZ restoration in DMO.

Spectral domain optical coherence tomography based imaging biomarkers for diabetic retinopathy

To evaluate the role of central subfield thickness (CST), cube average thickness (CAT), and cube volume (CV) as imaging biomarkers for severity of diabetic retinopathy within the ETDRS-based grades of retinopathy using spectral domain optical coherence tomography (SD-OCT). This study aims to evaluate the role of macular CST, CAT, and CV on SD-OCT as imaging biomarkers for severity of DR. One hundred ninety-four consecutive cases of type 2 diabetes mellitus were divided according to ETDRS classification: diabetes mellitus without retinopathy (No DR; n = 65), nonproliferative diabetic retinopathy (NPDR; n = 66), and proliferative diabetic retinopathy (PDR; n = 63). Sixty-three healthy controls were included. CST, CAT, and CV were analyzed using SD-OCT. Data were analyzed statistically. Analysis of variance revealed a significant increase in levels of CST, CAT, CV, and LogMAR visual acuity with the increase in severity of DR. Independent t-test revealed significant difference in CST, CAT, and CV between cases with DME and cases without DME. On multivariate linear regression analysis, increase in CST, CAT, and CV were found to indicate the increase in severity of DR. SD-OCT-based imaging biomarkers CST, CAT, and CV are effective tools for documenting the severity of diabetic retinopathy. These imaging biomarkers serve as significant indicators of severity of disease.

Multifocal electroretinogram in diabetic macular edema and its correlation with different optical coherence tomography features

PURPOSE

To evaluate multifocal electroretinogram (mfERG) parameters in eyes with diabetic macular edema (DME) and its correlation with vision and optical coherence tomography (OCT) features.

METHODS

Fifty-four eyes of 27 subjects with DME due to nonproliferative diabetic retinopathy were evaluated. MfERG responses were measured in three concentric rings. Macular thickness was measured by OCT in each segment of the three concentric rings, and mfERG rings were superimposed on the macular thickness map. The correlation between macular thickness in specific points of the thickness map and changes of the mfERG parameters in the corresponding points of the mfERG field map was evaluated and the relationship between the OCT and mfERG changes and changes of best-corrected visual acuity (BCVA) was investigated. The central foveal B-scans of SD-OCT were used to evaluate any correlation between the external limiting membrane (ELM) status, ellipsoid zone (EZ) status, presence of cysts or disorganization of retinal inner layers (DRIL), and mfERG parameters at the central corresponding area.

RESULTS

The mean of BCVA was 0.5 ± 0.3 in logMAR, and the central macular thickness was 392.6 ± 123.4 microns. The central ring P1 and N2 amplitudes had a significant correlation with BCVA in univariate and multivariate analyses (P = 0.001 for both, r = - 0.346 and r = - 0.646, respectively). There was a significant correlation between retinal thickness and the N1 amplitude in the central ring (P = 0.02, r = - 0.343). Outer retinal layer disruption (ELM and EZ) correlated with prolonged P1 implicit time at the corresponding location (P = 0.005, r = 0.068). The presence of the DRIL was associated with reduced P1 and N2 amplitudes (P = 0.037, r = - 0.284 and P = 0.019, r = - 0.562, respectively). A significant correlation was also found between the presence of cysts and a lower central P1 amplitude (P = 0.033, r = - 0.376).

CONCLUSION

In diabetic patients, discrete changes of some parameters in the central ring of the mfERG field map (e.g., P1 and N2 amplitudes) have a significant correlation with both structural OCT abnormalities in the corresponding points of the thickness map (like DRIL, intraretinal cyst and ELM/EZ disruption) and BCVA. Predictive models such as those described in this report may make it possible to identify the relationship between specific anatomical and functional characteristics in diabetic retinopathy.

Comparison of systemic conditions at diagnosis between central retinal vein occlusion and branch retinal vein occlusion

Objective

To compare systemic conditions at the time of diagnosis between patients with central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO).

Design

This study included patients diagnosed with CRVO or BRVO between February 2009 and August 2017 at three branch hospitals of Hallym University Medical Center. Demographic and anthropometric variables, systemic comorbidity profiles, and laboratory findings at diagnosis were collected from a clinical data warehouse system, and were compared between the CRVO and BRVO groups.

Result

Four hundred and seventeen patients with CRVO and 1,511 patients with BRVO were included. The mean age was 61.8 ± 13.9 years, which was comparable between two groups (P = .332). Female proportion was higher in the BRVO group (55.0%) than in the CRVO group (48.0%; P = .013). Diabetes mellitus (P = .017) and chronic kidney disease (P = .004) were more prevalent in the CRVO group. Serum homocysteine level was abnormally high in 23.5% of CRVO patients and in 8.4% of BRVO patients (P < .001). Blood urea nitrogen and serum creatinine levels were abnormally elevated in more subjects with CRVO (P = .002).

Conclusion

CRVO is associated with higher prevalence of diabetes mellitus and chronic kidney disease, as well as with elevated serum homocysteine level. These results might suggest a difference between the pathophysiologies of CRVO and BRVO.

Disorganization of retinal inner layers correlates with ellipsoid zone disruption and retinal nerve fiber layer thinning in diabetic retinopathy

PURPOSE

To study the correlation between disorganization of inner retinal layer (DRIL) and macular thickness parameters, ellipsoid zone (EZ) disruption and retinal nerve fiber layer (RNFL) thickness on spectral domain optical coherence tomography (SD-OCT) in diabetic retinopathy (DR), for the first time.

METHODS

A tertiary care center-based cross-sectional study was undertaken. One hundred and four consecutive study subjects of type 2 diabetes mellitus were included: diabetes mellitus with no retinopathy (No DR) (n = 26); non-proliferative DR (NPDR) (n = 26); proliferative DR (PDR) (n = 26) and healthy controls (n = 26). Best Corrected Visual Acuity (BCVA) was measured on the logarithm of the minimum angle of resolution (logMAR) scale. Clinician-friendly, SD-OCT based, grading systems were created for DRIL and EZ disruption, within the macular cube. DRIL was graded as: grade 0, DRIL absent; and grade 1, DRIL present. EZ disruption was graded as; Grade 0: Intact EZ; Grade 1: Focal disruption and Grade 2: Global disruption. Every study subject underwent RNFL thickness analysis.

RESULTS

DRIL was significantly associated with increase in severity of DR.Pearson correlation analysis showed significant positive correlation between DRIL and CST CAT and grades of EZ disruption . However, a significant negative correlation was found between DRIL and RNFL thickness .

CONCLUSION

Presence of DRIL correlates with severity of DR, EZ disruption and RNFL thinning.

Predictive Value of Baseline Biochemical Parameters for Clinical Response of Macular Edema to Bevacizumab in Eyes With Central Retinal Vein Occlusion: A Retrospective Analysis

PURPOSE

To evaluate the influence of baseline biochemical parameters on the improvement in best corrected visual acuity (BCVA) and reduction in central foveal thickness (CFT) in patients treated with intravitreal bevacizumab (IVB; Avastin, Genentech, Inc) for macular edema (ME) secondary to central retinal vein occlusion (CRVO).

DESIGN

A retrospective study.

METHODS

Seventy eyes of 70 participants with CRVO who underwent IVB for ME and had at least 1 month of follow-up after the last injection were studied. Demographic variables, systolic and diastolic blood pressure (SBP and DBP), BCVA, CFT measured by optical coherence tomography (OCT), and biochemical investigations [hemoglobin, fasting and postprandial blood sugar (FBS and PPBS), lipid profile, blood urea (BU), serum creatinine (SC), glycosylated hemoglobin (HbA1c)] at baseline were noted. IVB need at every visit was based on clinical and OCT parameters. Changes in BCVA (ΔBCVA) and CFT (ΔCFT) from baseline to last injection were estimated.

RESULTS

After IVB, there was a statistically significant reduction in mean CFT (P < 0.01). The group of patients with normal BU and SC had more than 2 lines of improvement compared with those with elevated values (P = 0.043 and 0.009, respectively). Other parameters like FBS, PPBS, hemoglobin, HbA1c, and serum lipids were not associated with improvement of BCVA and reduction of CFT.

CONCLUSIONS

Normal baseline renal parameters (BU and SC) predict better visual outcome after treatment for ME in CRVO and offer additional benefit over and above that obtained with ME reduction.

The potential of spectral domain optical coherence tomography imaging based retinal biomarkers

Background

Biomarker”, a merged word of “biological marker”, refers to a broad subcategory of medical signs that objectively indicate the state of health, and well-being of an individual. Biomarkers hold great promise for personalized medicine as information gained from diagnostic or progression markers can be used to tailor treatment to the individual for highly effective intervention in the disease process. Optical coherence tomography (OCT) has proved useful in identifying various biomarkers in ocular and systemic diseases.

Main body

Spectral domain optical coherence tomography imaging-based biomarkers provide a valuable tool for detecting the earlier stages of the disease, tracking progression, and monitoring treatment response. The aim of this review article is to analyze various OCT based imaging biomarkers and their potential to be considered as surrogate endpoints for diabetic retinopathy, age related macular degeneration, retinitis pigmentosa and vitreomacular interface disorder. These OCT based surrogate markers have been classified as retinal structural alterations (macular central subfield thickness and cube average thickness); retinal ultrastructural alterations (disruption of external limiting membrane and ellipsoid zone, thinning of retinal nerve fiber layer and ganglion cell layer); intraretinal microangiopathic changes; choroidal surrogate endpoints; and vitreoretinal interface endpoints.

Conclusion

OCT technology is changing very quickly and throughout this review there are some of the multiple possibilities that OCT based imaging biomarkers will be more useful in the near future for diagnosis, prognosticating disease progression and as endpoint in clinical trials.