Early neurodegeneration in the retina of type 2 diabetic patients

Multimodal imaging in diabetic retinopathy and macular edema: An update about biomarkers

Diabetic macular edema (DME), defined as retinal thickening near, or involving the fovea caused by fluid accumulation in the retina, can lead to vision impairment and blindness in patients with diabetes. Current knowledge of retina anatomy and function and DME pathophysiology has taken great advantage of the availability of several techniques for visualizing the retina. Combining these techniques in a multimodal imaging approach to DME is recommended to improve diagnosis and to guide treatment decisions. We review the recent literature about the following retinal imaging technologies: optical coherence tomography (OCT), OCT angiography (OCTA), wide-field and ultrawide-field techniques applied to fundus photography, fluorescein angiography, and OCTA. The emphasis will be on characteristic DME features identified by these imaging technologies and their potential or established role as diagnostic, prognostic, or predictive biomarkers. The role of artificial intelligence in the assessment and interpretation of retina images is also discussed.

Association between polygenic risk for schizophrenia and retinal morphology: A cross-sectional analysis of the United Kingdom Biobank

We examined the relationship between genetic risk for schizophrenia (SZ), using polygenic risk scores (PRSs), and retinal morphological alterations. Retinal structural and vascular indices derived from optical coherence tomography (OCT) and color fundus photography (CFP) and PRSs for SZ were analyzed in N = 35,024 individuals from the prospective cohort study, United Kingdom Biobank (UKB). Results indicated that macular ganglion cell-inner plexiform layer (mGC-IPL) thickness was significantly inversely related to PRS for SZ, and this relationship was strongest within higher PRS quintiles and independent of potential confounders and age. PRS, however, was unrelated to retinal vascular characteristics, with the exception of venular tortuosity, and other retinal structural indices (macular retinal nerve fiber layer [mRNFL], inner nuclear layer [INL], cup-to-disc ratio [CDR]). Additionally, the association between greater PRS and reduced mGC-IPL thickness was only significant for participants in the 40-49 and 50-59 age groups, not those in the 60-69 age group. These findings suggest that mGC-IPL thinning is associated with a genetic predisposition to SZ and may reflect neurodevelopmental and/or neurodegenerative processes inherent to SZ. Retinal microvasculature alterations, however, may be secondary consequences of SZ and do not appear to be associated with a genetic predisposition to SZ.

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.

Changes in foveal avascular zone parameters in individuals with prediabetes compared to normoglycemic controls: a systematic review and meta-analysis

To investigate changes in foveal avascular zone parameters in individuals with prediabetes compared to normoglycemic controls. PUBMED, Scopus and Cochrane Library were searched for published articles comparing the foveal avascular zone between prediabetic individuals and normoglycemic controls as assessed by optical coherence tomography angiography (OCTA). Standardised Mean Difference (SMD) with 95% confidence interval (CI) was computed for the comparison. A total of seven studies were included in our analysis, 6 provided data for the superficial capillary plexus from 345 eyes of individuals with prediabetes and 347 eyes of controls and 4 provided data on the deep capillary plexus from 285 eyes from individuals with prediabetes and 325 eyes of controls. Foveal avascular zone (FAZ) area in the superficial capillary plexus was enlarged in individuals with prediabetes compared to normoglycemic controls (SMD = 0.23, 95% CI = 0.03-0.44, p = 0.03, I2 = 27%, 6 studies). There was no statistically significant change in the deep capillary plexus FAZ area between the two groups (SMD = 1.14, 95% CI = -0.06-2.34, p = 0.06, I2 = 97%, 4 studies). FAZ area in the superficial capillary plexus was larger in individuals diagnosed with prediabetes compared to normoglycemic controls. This finding suggests that prediabetes could induce retinal microvascular changes before the onset of clinical diabetes. More original studies are needed to validate the results of the current meta-analysis.

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.

Macular Neural and Microvascular Alterations in Type 2 Diabetes Without Retinopathy: A SS-OCT Study

PURPOSE

To identify specific markers indicative of macular neural and microvascular alterations in individuals with Type 2 Diabetes Mellitus (T2DM) without clinically observable retinopathy.

DESIGN

Prospective cross-sectional study.

METHODS

Using the PLEX Elite 9000, all eyes underwent swept-source optical coherence tomography (SS-OCT) angiography. Quantitative analysis of acquired images compared macular neural and microvascular alterations in T2DM patients without retinopathy to age-matched controls. Precise assessments encompassed measuring the thickness of each individual retinal layer and evaluating macular vascular indices within different capillary plexuses.

RESULTS

Forty-nine T2DM patients and 51 age-matched controls participated. T2DM patients exhibited a significant reduction in the mean macular thickness of the ganglion cell-inner plexiform layer (GC-IPL) (82.5 ± 5.5 µm vs 86.2 ± 5.0 µm, P = .001) and macular retinal nerve fiber layer (RNFL) (45.8 ± 3.0 µm vs 48.1 ± 3.7 µm, P = .001). Furthermore, macular full retinal thickness was significantly lower in diabetic eyes than controls (324.9 ± 16.3 µm vs 332.8 ± 13.7 µm, P = .009). Vascular measurements revealed subtle changes in macular vascular skeleton density within the total capillary plexuses in T2DM patients (0.132 ± 0.005 vs 0.135 ± 0.005, P = .019).

CONCLUSIONS

Metrics derived from SS-OCT, particularly macular RNFL and GC-IPL thicknesses, emerged as superior indicators for the early detection of diabetic retinal disease in individuals with T2DM without clinically observable retinopathy. Further investigations are warranted to comprehensively understand the clinical implications of these findings.

Glucose tolerance and insulin resistance/sensitivity associate with retinal layer characteristics: the LIFE-Adult-Study

AIMS/HYPOTHESIS

As the prevalence of insulin resistance and glucose intolerance is increasing throughout the world, diabetes-induced eye diseases are a global health burden. We aim to identify distinct optical bands which are closely related to insulin and glucose metabolism, using non-invasive, high-resolution spectral domain optical coherence tomography (SD-OCT) in a large, population-based dataset.

METHODS

The LIFE-Adult-Study randomly selected 10,000 participants from the population registry of Leipzig, Germany. Cross-sectional, standardised phenotyping included the assessment of various metabolic risk markers and ocular imaging, such as SD-OCT-derived thicknesses of ten optical bands of the retina. Global and Early Treatment Diabetic Retinopathy Study (ETDRS) subfield-specific optical retinal layer thicknesses were investigated in 7384 healthy eyes of 7384 participants from the LIFE-Adult-Study stratified by normal glucose tolerance, prediabetes (impaired fasting glucose and/or impaired glucose tolerance and/or HbA1c 5.7-6.4% [39-47 mmol/mol]) and diabetes. The association of optical retinal band characteristics with different indices of glucose tolerance (e.g. fasting glucose, area under the glucose curve), insulin resistance (e.g. HOMA2-IR, triglyceride glucose index), or insulin sensitivity (e.g. estimated glucose disposal rate [eGDR], Stumvoll metabolic clearance rate) was determined using multivariable linear regression analyses for the individual markers adjusted for age, sex and refraction. Various sensitivity analyses were performed to validate the observed findings.

RESULTS

In the study cohort, nine out of ten optical bands of the retina showed significant sex- and glucose tolerance-dependent differences in band thicknesses. Multivariable linear regression analyses revealed a significant, independent, and inverse association between markers of glucose intolerance and insulin resistance (e.g. HOMA2-IR) with the thickness of the optical bands representing the anatomical retinal outer nuclear layer (ONL, standardised β=-0.096; p<0.001 for HOMA2-IR) and myoid zone (MZ; β=-0.096; p<0.001 for HOMA2-IR) of the photoreceptors. Conversely, markers of insulin sensitivity (e.g. eGDR) positively and independently associated with ONL (β=0.090; p<0.001 for eGDR) and MZ (β=0.133; p<0.001 for eGDR) band thicknesses. These global associations were confirmed in ETDRS subfield-specific analyses. Sensitivity analyses further validated our findings when physical activity, neuroanatomical cell/tissue types and ETDRS subfield categories were investigated after stratifying the cohort by glucose homeostasis.

CONCLUSIONS/INTERPRETATION

An impaired glucose homeostasis associates with a thinning of the optical bands of retinal ONL and photoreceptor MZ. Changes in ONL and MZ thicknesses might predict early metabolic retinal alterations in diabetes.

Tandem Mass Tag LC-MS/MS of Aqueous Humor From Individuals With Type 2 Diabetes Without Retinopathy Reveals Early Dysregulation of Synaptic Proteins

Purpose

An early neurodegenerative component of diabetic retinal disease (DRD) that precedes the vascular findings of clinically diagnosed diabetic retinopathy (DR) is increasingly being recognized. However, the relevant molecular mechanisms and biomarkers for early DRD are poorly defined. The purpose of this study was to uncover novel potential mediators of early diabetic retinal neuronal dysfunction through analysis of the aqueous fluid proteome in preclinical DR.

Methods

Aqueous fluid was collected from subjects with type 2 diabetes mellitus (DM) but no clinical DR and from nondiabetic controls undergoing routine cataract surgery. Preoperative spectral-domain optical coherence tomography of the macula was obtained. Tandem mass tag LC-MS/MS was performed to identify proteins differentially present in diabetic and control aqueous fluid, and proteins with >50% change and P < 0.05 were considered significant. Selected results were validated with western blot of human aqueous fluid samples.

Results

We identified decreased levels of proteins implicated in neuronal synapse formation and increased levels of inflammatory proteins in the aqueous fluid from patients with type 2 DM but no DR compared with controls. Of the differentially present synaptic proteins that we identified and confirmed with western blot, the majority have not previously been linked with DRD.

Conclusions

The proteomic profile of aqueous fluid from individuals with type 2 DM but no DR suggests that retinal neuronal dysfunction and inflammation represent very early events in the pathophysiology of DRD. These findings support the concept that diabetic retinal neurodegeneration precedes vascular pathology and reveal novel potential mediators and/or biomarkers warranting further investigation.

Retinal nerve fiber layer and ganglion cell complex thickness in diabetic smokers without diabetic retinopathy

PURPOSE

To compare the thickness of the retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GC-IPL) in smoker and nonsmoker diabetics without diabetic retinopathy.

MATERIALS AND METHODS

Patients with diabetes were divided into two groups according to their smoking status: Group 1 consisted of 38 smoker diabetics who had chronically smoked more than 20 cigarettes per day for more than five years; Group 2 consisted of 38 nonsmoker diabetics. After a detailed ophthalmologic examination, the mean and regional (superior, supratemporal, inferior, inferotemporal, temporal, nasal, superonasal, and inferonasal) RNFL and GC-IPL thicknesses were measured with spectral-domain optic coherence tomography (SD-OCT) and compared between groups.

RESULTS

The mean age was 54.7 ± 10.5 and 51.2 ± 9.7 years in the smoker and nonsmoker groups, respectively (p = 0.14). Gender, duration of diabetes, and the mean axial length were similar between groups (p:0.43, p:0.54, p: 0.52, respectively). Mean RNFL thickness was 89.1 ± 8.0 µm in the smoker group and 93.4 ± 7.0 µm in the nonsmoker group, and it was significantly thinner in the smoker group (p = 0.01). The temporal RNFL thickness in the smoker group was thinner than in the nonsmoker group (p = 0.02). There was no difference in superior, inferior, and nasal RNFL thicknesses between the groups (p = 0.31, p = 0.12, p = 0.39, respectively). The mean macular GC-IPL thickness of the smoker and nonsmoker groups was 78.53 ± 15.74 µm and 83.08 ± 5.85 µm, respectively (p = 0.09). Superior, superonasal, inferonasal, inferior, inferotemporal, and superotemporal quadrant GC-IPL thicknesses were similar between the groups (p = 0.07, p = 0.60, p = 0.55, p = 0.77, p = 0.71, p = 0.08, respectively). The groups showed no difference in minimum GC-IPL thickness (p = 0.43). There was a significant negative correlation between smoking exposure and mean, inferior quadrant RNFL thicknesses in the smoker group (p = 0.04, r= -0.32, and p = 0.01, r= -0.39, respectively).

CONCLUSION

Mean RNFL thickness was significantly thinner in smoker diabetics. Although not statistically significant, especially mean, superior, and superotemporal GC-IPL was thinner in smoker diabetics. The results suggest a potential association between the coexistence of diabetes and smoking with alterations in RNFL and GC-IPL thickness.

Retinal Function in Long-Term Type 1 Diabetes without Retinopathy: Insights from Pattern Electroretinogram and Pattern Visual Evoked Potentials Assessments

BACKGROUND

To evaluate changes in pattern electroretinogram (pERG) and pattern visual evoked potentials (pVEP) in patients with long-lasting type 1 diabetes without diabetic retinopathy (DR).

METHODS

Prospective study involving 92 eyes divided into two groups. The diabetic group included 46 eyes of 23 patients with type 1 diabetes (T1DM); the control group included 23 age-matched healthy subjects. pERG and pVEP were assessed using the RETI-port/scan21 recording software (version 1021.3.0.0).

RESULTS

Mean age was 48 ± 9.77 years for the diabetic group and 51.7 ± 4.75 years for the control group. The mean duration of diabetes was 28.88 ± 8.04 years. The mean HbA1c value was 7.29 ± 0.89%. There were no differences in the age or sex distribution. Regarding the pERG, T1DM patients exhibited a significant decrease in the amplitude of the P50 and N95 waves compared to the control group (p = 0.018 and p = 0.035, respectively), with no differences in the peak time of each component. pVEP showed no significant changes in either peak time or amplitude of the different components.

CONCLUSIONS

Long-term T1DM patients without DR showed changes in the amplitude of pERG waves with preserved peak times. We did not observe modifications in pVEP. pERG may serve as a subclinical marker of ganglion cell damage in long-term T1DM patients.

The Interplay between Neurotransmitters and Calcium Dynamics in Retinal Synapses during Development, Health, and Disease

The intricate functionality of the vertebrate retina relies on the interplay between neurotransmitter activity and calcium (Ca2+) dynamics, offering important insights into developmental processes, physiological functioning, and disease progression. Neurotransmitters orchestrate cellular processes to shape the behavior of the retina under diverse circumstances. Despite research to elucidate the roles of individual neurotransmitters in the visual system, there remains a gap in our understanding of the holistic integration of their interplay with Ca2+ dynamics in the broader context of neuronal development, health, and disease. To address this gap, the present review explores the mechanisms used by the neurotransmitters glutamate, gamma-aminobutyric acid (GABA), glycine, dopamine, and acetylcholine (ACh) and their interplay with Ca2+ dynamics. This conceptual outline is intended to inform and guide future research, underpinning novel therapeutic avenues for retinal-associated disorders.

Changes in Neurodegeneration and Visual Prognosis in Branch Retinal Vein Occlusion after Resolution of Macular Edema

This study aimed to examine the thicknesses of the ganglion cell layer (GCL) and peripapillary retinal nerve fiber layer (RNFL) in eyes with resolved macular edema (ME) in branch retinal vein occlusion (BRVO) and determine their relationship with visual acuity (VA). This retrospective observational case-control study included 57 eyes of BRVO patients with resolved ME after treatment. The macular GCL thickness, peripapillary RNFL thickness, and central macular thickness (CMT) measured on swept-source optical coherence tomography scans with the contralateral eyes used as controls were evaluated. The mean CMT was 270.48 ± 32.7 μm; the mean RNFL thickness was 105.46 ± 25.94 μm in BRVO eyes. Although the average RNFL thickness was decreased in BRVO eyes compared to unaffected eyes, there was no significant difference between the groups. However, the temporal and nasal RNFL thicknesses were significantly different between the groups. The mean affected quadrant had a significantly thinner GCL compared to the corresponding opposite unaffected quadrant (p = 0.02). Final VA was significantly correlated with nasal and middle GCL thicknesses in the affected area (r = -0.512, p = 0.003 and r = -0.537, p = 0.001, respectively); no correlation was found between the average RNFL thickness and mean CMT. The peripapillary RNFL and GCL thicknesses of the affected area were reduced in BRVO eyes compared to unaffected eyes. VA significantly correlated with nasal and middle GCL thicknesses in the affected area. Inner retinal damage occurring in patients with ME secondary to BRVO may be related to the visual prognosis.

Significant loss of retinal nerve fibre layer and contrast sensitivity in people with well controlled HIV disease: implications for aging with HIV

Objective

Antiretroviral therapy has decreased the prevalence of retinal opportunistic infections in people living with HIV (PLWH). However, abnormalities in visual function are evident and may be associated with an early onset of aging in PLWH. In this study, we examined the Retinal Nerve Fibre Layer (RNFL) thickness and visual function in PLWH and HIV non-infected controls in Malaysia.

Design

Cross-sectional study.

Methods

Two hundred and two (202) PLWH without retinal opportunistic infection and 182 age-matched, HIV seronegative individuals were enrolled. PLWH were recruited from the Infectious Disease clinic at the University Malaya Medical Centre. Controls were recruited among the hospital staff and community volunteers. RNFL thickness was measured with spectral domain optical coherence tomography (SDOCT). Visual functions include visual acuity using LogMAR chart and contrast sensitivity using Pelli- Robson Chart.

Results

All PLWH (mean age 46.1 years ± 9.9 years) in the study were on ART and 61.2% had a CD4+ T-cell count more than 500 cell/μl. The mean visual acuity was similar between the two groups (LogMAR 0.05 vs. 0.07, p = 0.115). Contrast sensitivity was lower in PLWH compared to HIV seronegative individuals (1.90 vs 1.93, p = 0.032). RNFL thickness was significantly thinner in the temporal quadrant for PLWH compared to controls (68.89 μm vs 74.08 μm, p = 0.001).

Conclusion

Changes in RNFL thickness and contrast sensitivity were seen in PLWH despite their relatively young age and well controlled HIV disease. The changes reflect structural and functional deficits, and could have long-term implications on their health trajectory.

Multimodal imaging analysis for the impact of retinal peripheral lesions on central neurovascular structure and retinal function in type 2 diabetes with diabetic retinopathy

OBJECTIVES

To explore the possible role of peripheral lesions (PLs) detected by ultrawide field (UWF) imaging system on central neurovascular structure and retinal function.

METHODS

Ninety-seven diabetic patients were included in this cross-sectional study using UWF pseudocolour colour imaging with Optos Daytona (Optos, PLC). UWF images were graded as with predominantly peripheral lesions (PPLs) and without PPL. Macular neurovascular alterations and retinal function were measured by optical coherence tomography angiography (OCTA) and RETeval device, respectively. Central microcirculation and retinal function were compared between eyes with and without PPL.

RESULTS

The study evaluated 186 eyes (97 patients; 43 females (44.3%)), including 92 eyes without PPL and 94 eyes with PPL. Central retinal vessel density was comparable between eyes with and without PPL. Delayed implicit time and decreased pupil area ratio were found in the PPL group compared with eyes without PPL, and this difference remained unchanged after adjusting for systemic factors (all p＜0.01).

CONCLUSIONS

Our study suggests that retinal function is worse in diabetic eyes with PPL. These findings challenged the conventional ETDRS protocols which ignored peripheral retina in determining DR severity. Furthermore, combining UWF imaging with RETeval system to detect more retinal abnormalities may be helpful in DR management.

Anti-VEGF combined with ocular corticosteroids therapy versus anti-VEGF monotherapy for diabetic macular edema focusing on drugs injection times and confounding factors of pseudophakic eyes: A systematic review and meta-analysis

PURPOSE

To assess the effectiveness and safety of combining intravitreal endothelial growth factor inhibitor (anti-VEGF) and ocular corticosteroids for diabetic macular edema (DME).

METHODS

Articles concentrating on the efficacy and safety of combining anti-VEGF and ocular corticosteroids therapy for DME versus anti-VEGF monotherapy was screened systematically. Meta-analysis was conducted on the basis of a protocol registered in the PROSPERO (CRD42023408338) and performed on the extracted continuous variables and dichotomous variables. The outcome was expressed as weighted mean difference (MD) and risk ratio (RR).

RESULTS

Add up to 21 studies including 1468 eyes were enrolled in this study. The MD for best-corrected visual acuity (BCVA) improvement at 1/3/6/12-month between the combination therapy group and monotherapy group were 2.56 (95% CI [0.43, 4.70]), 2.46 (95% CI [-0.40, 5.32]), - 1.76 (95% CI [-3.18, -0.34]), - 1.94 (95% CI [-3.87, 0.00]), respectively. The MD for central retinal thickness (CMT) reduction at 1/3/6/12-month between two groups were - 66.27 (95% CI [-101.08, -31.47]), - 33.62 (95% CI [-57.55, -9.70]), - 4.54 (95% CI [-16.84, 7.76]), - 26.67 (95% CI [-41.52, -11.82]), respectively. Additionally, the combination group had higher relative risk of high intraocular pressure and cataract progression events.

CONCLUSIONS

Anti-VEGF combined with ocular corticosteroids had a significant advantage over anti-VEGF monotherapy within 3 months of DME treatment, which reached the maximum with increasing anti-VEGF injection times to 3. However, with the prolongation of the treatment cycle, the effect of combined therapy after 6 months was no better than monotherapy, and the side effects of combined therapy were more severe.

Retinal Neurodegeneration as a Potential Biomarker of Accelerated Aging in Schizophrenia Spectrum Disorders

BACKGROUND AND HYPOTHESES

Several biological markers are believed to reflect accelerated aging in schizophrenia spectrum disorders; however, retinal neural changes have not yet been explored as potential CNS biomarkers of accelerated aging in this population. The aim of this study was to determine whether retinal neural layer thinning is more strongly related to age in schizophrenia and schizoaffective disorder patients (SZ) than in a psychiatrically healthy control group (CON).

STUDY DESIGN

Schizophrenia (n = 60) and CON participants (n = 69) underwent spectral domain optical coherence tomography (OCT) scans to examine the following variables in both eyes: retinal nerve fiber layer (RNFL) thickness, macula central subfield (CSF) thickness, macula volume, ganglion cell layer-inner plexiform layer (GCL-IPL) thickness, optic cup volume, and cup-to-disc ratio. Eleven participants in each group had diabetes or hypertension.

STUDY RESULTS

Significant negative relationships between age and RNFL thickness, macula volume, and GCL-IPL thickness were observed in the SZ group, while no significant relationships were observed in the CON group. However, many of the findings in the SZ group lost significance when participants with diabetes/hypertension were removed from analyses. A notable exception to this was that the age × SZ interaction accounted for a unique proportion of variance in GCL-IPL thinning over and above the effect of diabetes/hypertension.

CONCLUSIONS

The results suggest that retinal atrophy occurs at an increased rate in schizophrenia spectrum disorders, potentially reflecting accelerated aging inherent to these conditions, with considerable contributions from systemic medical diseases closely linked to this population.

Objective perimetry identifies regional functional progression and recovery in mild Diabetic Macular Oedema

PURPOSE

Retinal function beyond foveal vision is not routinely examined in the clinical screening and management of diabetic retinopathy although growing evidence suggests it may precede structural changes. In this study we compare optical coherence tomography (OCT) based macular structure with function measured objectively with the ObjectiveFIELD Analyzer (OFA), and with Matrix perimetry. We did that longitudinally in Type 2 diabetes (T2D) patients with mild Diabetic Macular Oedema (DMO) with good vision and a similar number of T2D patients without DMO, to evaluate changes in retinal function more peripherally over the natural course of retinopathy.

METHODS

Both eyes of 16 T2D patients (65.0 ± 10.1, 10 females), 10 with baseline DMO, were followed for up longitudinally for 27 months providing 94 data sets. Vasculopathy was assessed by fundus photography. Retinopathy was graded using to Early Treatment of Diabetic Retinopathy Study (ETDRS) guidelines. Posterior-pole OCT quantified a 64-region/eye thickness grid. Retinal function was measured with 10-2 Matrix perimetry, and the FDA-cleared OFA. Two multifocal pupillographic objective perimetry (mfPOP) variants presented 44 stimuli/eye within either the central 30° or 60° of the visual field, providing sensitivities and delays for each test-region. OCT, Matrix and 30° OFA data were mapped to a common 44 region/eye grid allowing change over time to be compared at the same retinal regions.

RESULTS

In eyes that presented with DMO at baseline, mean retinal thickness reduced from 237 ± 25 μm to 234.2 ± 26.7 μm, while the initially non-DMO eyes significantly increased their mean thickness from 250.7 ± 24.4 μm to 255.7 ± 20.6 μm (both p<0.05). Eyes that reduced in retinal thickness over time recovered to more normal OFA sensitivities and delays (all p<0.021). Matrix perimetry quantified fewer regions that changed significantly over the 27 months, mostly presenting in the central 8 degrees.

CONCLUSIONS

Changes in retinal function measured by OFA possibly offer greater power to monitor DMO over time than Matrix perimetry data.

Quantitatively Evaluating the Relationships between Insulin Resistance and Retinal Neurodegeneration with Optical Coherence Tomography in Early Type 2 Diabetes Mellitus

INTRODUCTION

The aim of this study was to quantitatively assess retinal neurodegenerative changes with optical coherence tomography (Cirrus HD-OCT) in type 2 diabetes mellitus (T2DM) patients without diabetic retinopathy (DR) and evaluate their relationships with insulin resistance (IR) and associated systemic indicators.

METHODS

102 T2DM patients without DR and 48 healthy controls were included in this observational cross-sectional study. The OCT parameters of macular retinal thickness (MRT) and ganglion cell-inner plexiform layer (GCIPL) thicknesses were evaluated between diabetic and normal eyes. The receiver operating characteristics (ROC) curve was generated to evaluate the discrimination power of early diabetes. Correlation and multiple regression analysis were performed between ophthalmological parameters and T2DM-related demographic and anthropometric variables, and serum biomarkers and homeostasis model assessment of insulin resistance (HOMA-IR) scores.

RESULTS

MRT and GCIPL thicknesses showed significant thinning in patients, especially in inferotemporal area. High body mass index (BMI) correlated with decreased GCIPL thicknesses and elevated intraocular pressure (IOP). A negative correlation between waist-to-hip circumference ratio (WHR) and GCIPL thicknesses was also found. High-density lipoprotein (HDL) and fasting C-peptide (CP0) were associated with GCIPL thickness but only in inferotemporal region (r = 0.20, p = 0.04; r = -0.20, p = 0.05, respectively). Multiple regression analysis showed that increased HOMA-IR scores independently predicted both average (β = -0.30, p = 0.05) and inferotemporal (β = -0.34, p = 0.03) GCIPL thinning.

CONCLUSION

Retinal thinning in early T2DM was associated with obesity-related metabolic disorders. IR as an independent risk factor for retinal neurodegeneration may increase the risk of developing glaucoma.

Current Treatments for Diabetic Macular Edema

Diabetic retinopathy is a major retinal disorder and a leading cause of blindness. Diabetic macular edema (DME) is an ocular complication in patients with diabetes, and it can impair vision significantly. DME is a disorder of the neurovascular system, and it causes obstructions of the retinal capillaries, damage of the blood vessels, and hyperpermeability due to the expression and action of vascular endothelial growth factor (VEGF). These changes result in hemorrhages and leakages of the serous components of blood that result in failures of the neurovascular units (NVUs). Persistent edema of the retina around the macula causes damage to the neural cells that constitute the NVUs resulting in diabetic neuropathy of the retina and a reduction in vision quality. The macular edema and NVU disorders can be monitored by optical coherence tomography (OCT). Neuronal cell death and axonal degeneration are irreversible, and their development can result in permanent visual loss. Treating the edema before these changes are detected in the OCT images is necessary for neuroprotection and maintenance of good vision. This review describes the effective treatments for the macular edema that are therefore neuroprotective.

Evaluation of retinal nerve fibre layer thickness as a possible measure of diabetic retinal neurodegeneration in the EPIC-Norfolk Eye Study

BACKGROUND/AIMS

Markers to clinically evaluate structural changes from diabetic retinal neurodegeneration (DRN) have not yet been established. To study the potential role of peripapillary retinal nerve fibre layer (pRNFL) thickness as a marker for DRN, we evaluated the relationship between diabetes, as well as glycaemic control irrespective of diabetes status and pRNFL thickness.

METHODS

Leveraging data from a population-based cohort, we used general linear mixed models (GLMMs) with a random intercept for patient and eye to assess the association between pRNFL thickness (measured using GDx) and demographic, systemic and ocular parameters after adjusting for typical scan score. GLMMs were also used to determine: (1) the relationship between: (A) glycated haemoglobin (HbA1c) irrespective of diabetes diagnosis and pRNFL thickness, (B) diabetes and pRNFL thickness and (2) which quadrants of pRNFL may be affected in participants with diabetes and in relation to HbA1c.

RESULTS

7076 participants were included. After controlling for covariates, inferior pRNFL thickness was 0.94 µm lower (95% CI -1.28 µm to -0.60 µm), superior pRNFL thickness was 0.83 µm lower (95% CI -1.17 µm to -0.49 µm) and temporal pRNFL thickness was 1.33 µm higher (95% CI 0.99 µm to 1.67 µm) per unit increase in HbA1c. Nasal pRNFL thickness was not significantly associated with HbA1c (p=0.23). Similar trends were noted when diabetes was used as the predictor.

CONCLUSION

Superior and inferior pRNFL was significantly thinner among those with higher HbA1c levels and/or diabetes, representing areas of the pRNFL that may be most affected by diabetes.

The link between glycemic control measures and eye microvascular complications in a clinical cohort of type 2 diabetes with microRNA-223-3p signature

BACKGROUND

Type 2 diabetes (T2D) is a critical healthcare challenge and priority in Qatar which is listed amongst the top 10 countries in the world, with its prevalence presently at 17% double the global average. MicroRNAs (miRNAs) are implicated in the pathogenesis of (T2D) and long-term microvascular complications including diabetic retinopathy (DR).

METHODS

In this study, a T2D cohort that accurately matches the characteristics of the general population was employed to find microRNA (miRNA) signatures that are correlated with glycemic and β cell function measurements. Targeted miRNA profiling was performed in (471) T2D individuals with or without DR and (491) (non-diabetic) healthy controls from the Qatar Biobank. Discovery analysis identified 20 differentially expressed miRNAs in T2D compared to controls, of which miR-223-3p was significantly upregulated (fold change:5.16, p = 3.6e-02) and positively correlated with glucose and hemoglobin A1c (HbA1c) levels (p-value = 9.88e-04 and 1.64e-05, respectively), but did not show any significant associations with insulin or C-peptide. Accordingly, we performed functional validation using a miR-223-3p mimic (overexpression) under control and hyperglycemia-induced conditions in a zebrafish model.

RESULTS

Over-expression of miR-223-3p alone was associated with significantly higher glucose (42.7 mg/dL, n = 75 vs 38.7 mg/dL, n = 75, p = 0.02) and degenerated retinal vasculature, and altered retinal morphology involving changes in the ganglion cell layer and inner and outer nuclear layers. Assessment of retinal angiogenesis revealed significant upregulation in the expression of vascular endothelial growth factor and its receptors, including kinase insert domain receptor. Further, the pancreatic markers, pancreatic and duodenal homeobox 1, and the insulin gene expressions were upregulated in the miR-223-3p group.

CONCLUSION

Our zebrafish model validates a novel correlation between miR-223-3p and DR development. Targeting miR-223-3p in T2D patients may serve as a promising therapeutic strategy to control DR in at-risk individuals.

Effects of Blood Pressure and Arterial Stiffness on Retinal Neurodegeneration: Cross-Sectional and Longitudinal Evidence From UK Biobank and Chinese Cohorts

BACKGROUND

Hypertension might be a modifiable risk factor for neurodegeneration diseases. However, the associations between blood pressure (BP), arterial stiffness index and retinal neurodegeneration remain unclear.

METHODS

This study used cross-sectional data from the United Kingdom BioBank (UKB) and longitudinal data from the Chinese Ocular Imaging Project (COIP). The macular ganglion cell-inner plexiform layer thickness (mGCIPLT) and macular retinal nerve fiber layer thickness were measured using spectral domain optical coherence tomography imaging. Swept-source optical coherence tomography was performed to obtain the longitudinal trajectory of the mGCIPLT and peripapillary retinal nerve fiber layer thickness in the COIP cohort. Multivariable linear models were used to analyze the associations between BP and retinal measurements.

RESULTS

In a cross-sectional analysis of 22 801 participants from UKB, thinner mGCIPLT was related to higher systolic BP (β: -0.103 [-0.146 to -0.061]; P<0.001), and higher diastolic BP (β: -0.191 [-0.265 to -0.117]; P<0.001), and was significantly associated with higher mean arterial pressure (β: -0.174 [-0.238 to -0.109]; P<0.001) and higher mean pulse pressure (β: -0.080 [-0.139 to -0.020]; P=009). In a longitudinal analysis of 2012 eligible COIP participants, higher levels of baseline systolic BP, diastolic BP, mean arterial pressure, and mean pulse pressure were associated with faster thinning in mGCIPLT and peripapillary retinal nerve fiber layer thickness (all P<0.001). The strongest association was the effect of mean arterial pressure on mGCIPLT (β: -0.118 [-0.175 to -0.061]; P<0.001). The results of the analysis of macular retinal nerve fiber layer thickness and peripapillary retinal nerve fiber layer thickness were consistent with those of mGCIPLT.

CONCLUSIONS

BP levels were independently and consistently associated with various retinal neurodegenerative exacerbations.

Visual Field Abnormalities in Early-Stage Diabetic Retinopathy Assessed by Chromatic Perimetry

Purpose

The purpose of this study was to define the nature and extent of sensitivity loss using chromatic perimetry in diabetics who have mild or no retinopathy.

Methods

Thirty-four individuals with type II diabetes mellitus who have mild nonproliferative diabetic retinopathy (MDR; N = 17) or no diabetic retinopathy (NDR; N = 17) and 15 visually normal, non-diabetic controls participated. Sensitivity was assessed along the horizontal visual field meridian using an Octopus 900 perimeter. Measurements were performed under light- and dark-adapted conditions using long-wavelength (red) and short-wavelength (blue) Goldmann III targets. Cumulative defect curves (CDCs) were constructed to determine whether field sensitivity loss was diffuse or localized.

Results

Sensitivity was reduced significantly under light-adapted conditions for both stimulus colors for the NDR (mean defect ± SEM = -2.1 dB ± 0.6) and MDR (mean defect ± SEM = -4.0 dB ± 0.7) groups. Sensitivity was also reduced under dark-adapted conditions for both stimulus colors for the NDR (mean defect ± SEM = -1.9 dB ± 0.7) and MDR (mean defect ± SEM = -4.5 ± 1.0 dB) groups. For both diabetic groups, field loss tended to be diffuse under light-adapted conditions (up to 6.9 dB loss) and localized under dark-adapted conditions (up to 15.4 dB loss).

Conclusions

Visual field sensitivity losses suggest neural abnormalities in early stage diabetic eye disease and the pattern of the sensitivity losses differed depending on the adaptation conditions. Chromatic perimetry may be useful for subtyping individuals who have mild or no diabetic retinopathy and for better understanding their neural dysfunction.

Elevated retinal retinol-binding protein 4 levels in diabetic mice can induce retinal neurodegeneration through microglia

Retinol-binding protein 4 (RBP4) is the sole specific transport protein for vitamin A (retinol), but it is also an adipokine with retinol-independent, proinflammatory activity associated with diabetes and diabetic retinopathy (DR). Most previous studies focused on the relationship between elevated serum RBP4 levels and DR. Since serum RBP4 cannot cross the blood-retinal barrier, the level of retinal RBP4 is independent of serum RBP4, and the change of retinal RBP4 and its potential pathogenic mechanism in DR has not been studied. We showed that the retinal RBP4 levels were raised in Streptozotocin-induced diabetic mice though the serum RBP4 levels were decreased. Intravitreal injection of RBP4 protein in mice results in activation of microglia, loss of retinal ganglion cells (RGCs) and bipolar cells. Minocycline (MC) can reverse the activation of microglia induced by RBP4, protecting RGCs and bipolar cells. These findings suggest that retinal RBP4 levels were raised in diabetic mice, and RBP4 can directly induce retinal neurodegeneration in mice through microglia. RESEARCH HIGHLIGHTS: We revealed that the retinal RBP4 levels were raised in diabetes and elevated retinal RBP4 can induce retinal neurodegeneration through microglia. Inhibition of neuroinflammation or reduction of retinal RBP4 level may be a potential therapeutic strategy to prevent diabetic retinal neurodegeration.

Associations Between HbA1c Across the Normal Range, Diagnosed, and Undiagnosed Diabetes and Retinal Layer Thickness in UK Biobank Cohort

Purpose

The purpose of this study was to investigate the association between glycated hemoglobin (HbA1c) levels and retinal sub-layer thicknesses in people with and without diabetes.

Methods

We included 41,453 UK Biobank participants aged 40 to 69 years old. Diabetes status was defined by self-report of diagnosis or use of insulin. Participants were categorized into groups: (1) those with HbA1c <48 mmol/mol were subdivided into quintiles according to normal range of HbA1c; (2) those previously diagnosed with diabetes with no evidence of diabetic retinopathy; and (3) undiagnosed diabetes: >48 mmol/mol. Total macular and retinal sub-layer thicknesses were derived from spectral-domain optical coherence tomography (SD-OCT) images. Multivariable linear regression was used to evaluate the associations between diabetes status and retinal layer thickness.

Results

Compared with participants in the second quintile of the normal HbA1c range, those in the fifth quintile had a thinner photoreceptor layer thickness (-0.33 µm, P = 0.006). Participants with diagnosed diabetes had a thinner macular retinal nerve fiber layer (mRNFL; -0.58 µm, P < 0.001), photoreceptor layer thickness (-0.94 µm, P < 0.001), and total macular thickness (-1.61 µm, P < 0.001), whereas undiagnosed diabetes participants had a reduced photoreceptor layer thickness (-1.22 µm, P = 0.009) and total macular thickness (-2.26 µm, P = 0.005). Compared to participants without diabetes, those with diabetes had a thinner mRNFL (-0.50 µm, P < 0.001), photoreceptor layer thickness (-0.77 µm, P < 0.001), and total macular thickness (-1.36 µm, P < 0.001).

Conclusions

Participants with higher HbA1c in the normal range had marginally thinner photoreceptor thickness, whereas those with diabetes (including undiagnosed diabetes) had meaningfully thinner retinal sublayer and total macular thickness.

Translational Relevance

We showed that early retinal neurodegeneration occurs in people whose HbA1c levels are below the current diabetes diagnostic threshold; this might impact the management of pre-diabetes individuals.

Optical coherence tomography as retinal imaging biomarker of neuroinflammation/neurodegeneration in systemic disorders in adults and children

The retina and the optic nerve are considered extensions of the central nervous system (CNS) and thus can serve as the window for evaluation of CNS disorders. Spectral domain optical coherence tomography (OCT) allows for detailed evaluation of the retina and the optic nerve. OCT can non-invasively document changes in single retina layer thickness and structure due to neuronal and retinal glial cells (RGC) modifications in systemic and local inflammatory and neurodegenerative diseases. These can include evaluation of retinal nerve fibre layer and ganglion cell complex, hyper-reflective retinal spots (HRS, sign of activated microglial cells in the retina), subfoveal neuroretinal detachment, disorganization of the inner retinal layers (DRIL), thickness and integrity of the outer retinal layers and choroidal thickness. This review paper will report the most recent data on the use of OCT as a non invasive imaging biomarker for evaluation of the most common systemic neuroinflammatory and neurodegenerative/neurocognitive disorders in the adults and in paediatric population. In the adult population the main focus will be on diabetes mellitus, multiple sclerosis, optic neuromyelitis, neuromyelitis optica spectrum disorders, longitudinal extensive transverse myelitis, Alzheimer and Parkinson diseases, Amyotrophic lateral sclerosis, Huntington's disease and schizophrenia. In the paediatric population, demyelinating diseases, lysosomal storage diseases, Nieman Pick type C disease, hypoxic ischaemic encephalopathy, human immunodeficiency virus, leukodystrophies spinocerebellar ataxia will be addressed.

Risk of diabetic retinopathy and retinal neurodegeneration in individuals with type 2 diabetes: Beichen Eye Study

Objective

Our aim was to evaluate associations of different risk factors with odds of diabetic retinopathy (DR) diagnosis and retinal neurodegeneration represented by macular ganglion cell-inner plexiform layer (mGCIPL).

Methods

This cross-sectional study analyzed data from individuals aged over 50 years examined between June 2020 and February 2022 in the community-based Beichen Eye Study on ocular diseases. Baseline characteristics included demographic data, cardiometabolic risk factors, laboratory findings, and medications at enrollment. Retinal thickness in both eyes of all participants was measured automatically via optical coherence tomography. Risk factors associated with DR status were investigated using multivariable logistic regression. Multivariable linear regression analysis was performed to explore associations of potential risk factors with mGCIPL thickness.

Results

Among the 5037 included participants with a mean (standard deviation, SD) age of 62.6 (6.7) years (3258 women [64.6%]), 4018 (79.8%) were control individuals, 835 (16.6%) were diabetic individuals with no DR, and 184 (3.7%) were diabetic individuals with DR. The risk factors significantly associated with DR status were family history of diabetes (odds ratio [OR], 4.09 [95% CI, 2.44-6.85]), fasting plasma glucose (OR, 5.88 [95% CI, 4.66-7.43]), and statins (OR, 2.13 [95% CI, 1.03-4.43]) relative to the control individuals. Compared with the no DR, diabetes duration (OR, 1.17 [95% CI, 1.13-1.22]), hypertension (OR, 1.60 [95% CI, 1.26-2.45]), and glycated hemoglobin A1C (HbA1c) (OR, 1.27 [95% CI, 1.00-1.59]) were significantly correlated with DR status. Furthermore, age (adjusted β = -0.19 [95% CI, -0.25 to -0.13] μm; P < 0.001), cardiovascular events (adjusted β = -0.95 [95% CI, -1.78 to -0.12] μm; P = 0.03), and axial length (adjusted β = -0.82 [95% CI, -1.29 to -0.35] μm; P = 0.001) were associated with mGCIPL thinning in diabetic individuals with no DR.

Conclusion

Multiple risk factors were associated with higher odds of DR development and lower mGCIPL thickness in our study. Risk factors affecting DR status varied among the different study populations. Age, cardiovascular events, and axial length were identified as potential risk factors for consideration in relation to retinal neurodegeneration in diabetic patients.

Classification of diabetic retinopathy: Past, present and future

Diabetic retinopathy (DR) is a leading cause of visual impairment and blindness worldwide. Since DR was first recognized as an important complication of diabetes, there have been many attempts to accurately classify the severity and stages of disease. These historical classification systems evolved as understanding of disease pathophysiology improved, methods of imaging and assessing DR changed, and effective treatments were developed. Current DR classification systems are effective, and have been the basis of major research trials and clinical management guidelines for decades. However, with further new developments such as recognition of diabetic retinal neurodegeneration, new imaging platforms such as optical coherence tomography and ultra wide-field retinal imaging, artificial intelligence and new treatments, our current classification systems have significant limitations that need to be addressed. In this paper, we provide a historical review of different classification systems for DR, and discuss the limitations of our current classification systems in the context of new developments. We also review the implications of new developments in the field, to see how they might feature in a future, updated classification.

Diabetes mellitus associated neurovascular lesions in the retina and brain: A review

Diabetes mellitus (DM) is now recognized as a system-wide, autoimmune, inflammatory, microvascular disorder, which, in the retina and brain results in severe multifocal injury now recognized as a leading cause, world-wide, of progressive vision loss and dementia. To address this problem, resulting primarily from variations in glycemia in the prediabetic and overt diabetic states, it must be realized that, although some of the injury processes associated with diabetes may be system wide, there are varying responses, effector, and repair mechanisms that differ from organ to organ or within varying cell structures. Specifically, within the retina, and similarly within the brain cortex, lesions occur of the "neurovascular unit", comprised of focal microvascular occlusions, inflammatory endothelial and pericyte injury, with small vessel leakage resulting in injury to astrocytes, Müller cells, and microglia, all of which occur with progressive neuronal apoptosis. Such lesions are now recognized to occur before the first microaneurysms are visible to imaging by fundus cameras or before they result in detectable symptoms or signs recognizable to the patient or clinician. Treatments, therefore, which currently are not initiated within the retina until edema develops or there is progression of vascular lesions that define the current staging of retinopathy, and in the brain only after severe signs of cognitive failure. Treatments, therefore are applied relatively late with some reduction in progressive cellular injury but with resultant minimal vision or cognitive improvement. This review article will summarize the multiple inflammatory and remediation processes currently understood to occur in patients with diabetes as well as pre-diabetes and summarize as well the current limitations of methods for assessing the structural and functional alterations within the retina and brain. The goal is to attempt to define future screening, monitoring, and treatment directions that hopefully will prevent progressive injury as well as enable improved repair and attendant function.

MicroRNA-150 (miR-150) and Diabetic Retinopathy: Is miR-150 Only a Biomarker or Does It Contribute to Disease Progression?

Diabetic retinopathy (DR) is a chronic disease associated with diabetes mellitus and is a leading cause of visual impairment among the working population in the US. Clinically, DR has been diagnosed and treated as a vascular complication, but it adversely impacts both neural retina and retinal vasculature. Degeneration of retinal neurons and microvasculature manifests in the diabetic retina and early stages of DR. Retinal photoreceptors undergo apoptosis shortly after the onset of diabetes, which contributes to the retinal dysfunction and microvascular complications leading to vision impairment. Chronic inflammation is a hallmark of diabetes and a contributor to cell apoptosis, and retinal photoreceptors are a major source of intraocular inflammation that contributes to vascular abnormalities in diabetes. As the levels of microRNAs (miRs) are changed in the plasma and vitreous of diabetic patients, miRs have been suggested as biomarkers to determine the progression of diabetic ocular diseases, including DR. However, few miRs have been thoroughly investigated as contributors to the pathogenesis of DR. Among these miRs, miR-150 is downregulated in diabetic patients and is an endogenous suppressor of inflammation, apoptosis, and pathological angiogenesis. In this review, how miR-150 and its downstream targets contribute to diabetes-associated retinal degeneration and pathological angiogenesis in DR are discussed. Currently, there is no effective treatment to stop or reverse diabetes-caused neural and vascular degeneration in the retina. Understanding the molecular mechanism of the pathogenesis of DR may shed light for the future development of more effective treatments for DR and other diabetes-associated ocular diseases.

A Comparative Study of Ganglion Cell Complex Thickness Changes in Diabetic Macular Edema and Central Retinal Vein Occlusion Macular Edema: An Optical Coherence Tomography Study

Aim This study aims to compare the ganglion cell complex changes in diabetic macular edema (DME) and central retinal vein occlusion (CRVO) macular edema using optical coherence tomography (OCT). Methods This was a hospital-based cross-sectional study conducted for six months. All patients having DME and CRVO macular edema presenting to the Ophthalmology Department at Acharya Vinobha Bhave Rural Hospital were included in the study. A detailed and comprehensive ophthalmic examination was performed, and OCT was done for each patient. Results The incidence of both DME and CRVO macular edema were both found to be maximum in the age group of 61-69 years. DME is more common in males (62.86%) than females (37.14%); the same was observed in CRVO group: 54.29% were males and 45.71% were females. Macular edema showed a mean value of 370.11 in DME and 428.71 in CRVO. Thus, the CRVO group showed more macular edema than the DME group. The ganglion cell complex thickness showed a mean value of 58.47 in DME and 66.77 in the CRVO group, implying that the thickness reduced significantly in the DME group. Conclusion OCT provides quantitative measurement of the ganglion cell complex thickness, which helps monitor the course of macular edema secondary to CRVO and diabetes Mellitus and thereby provides an assessment of the prognosis of the disease as these two diseases in particular are major causes of blindness worldwide, and timely care and management can help in altering its course.

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

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

Aryl hydrocarbon receptor deficiency augments dysregulated microangiogenesis and diabetic retinopathy

Diabetic retinopathy (DR) is a pathophysiologic vasculopathic process with obscure mechanisms and limited effective therapeutic strategies. Aryl hydrocarbon receptor (AhR) is an important regulator of xenobiotic metabolism and an environmental sensor. The aim of the present study was to investigate the role of AhR in the development of DR and elucidate the molecular mechanism of its downregulation. DR was evaluated in diabetes-induced retinal injury in wild type and AhR knockout (AhR-/-) mice. Retinal expression of AhR was determined in human donor and mice eyes by immunofluorescence since AhR activity was examined in diabetes. AhR knockout (AhRKO) mice were used to induce diabetes with streptozotocin, high-fat diet, or genetic double knockout with diabetes spontaneous mutation (Leprdb) (DKO; AhR-/-×Leprdb/db) for investigating structural, functional, and metabolic abnormalities in vascular and epithelial retina. Structural molecular docking simulation was used to survey the pharmacologic AhR agonists targeting phosphorylated AhR (Tyr245). Compared to diabetic control mice, diabetic AhRKO mice had aggravated alterations in retinal vasculature that amplified hallmark features of DR like vasopermeability, vascular leakage, inflammation, blood-retinal barrier breakdown, capillary degeneration, and neovascularization. AhR agonists effectively inhibited inflammasome formation and promoted AhR activity in human retinal microvascular endothelial cells and pigment epithelial cells. AhR activity and protein expression was downregulated, resulting in a decrease in DNA promoter binding site of pigment epithelium-derived factor (PEDF) by gene regulation in transcriptional cascade. This was reversed by AhR agonists. Our study identified a novel of DR model that target the protective AhR/PEDF axis can potentially maintain retinal vascular homeostasis, providing opportunities to delay the development of DR.

Thioredoxin-interacting protein in diabetic retinal neurodegeneration: A novel potential therapeutic target for diabetic retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes mellitus and has been considered a microvascular disease for a long time. However, recent evidence suggests that diabetic retinal neurodegeneration (DRN), which manifests as neuronal apoptosis, a decrease in optic nerve axons, and reactive gliosis, occurs prior to retinal microvascular alterations. Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of thioredoxin (Trx), and it acts by inhibiting its reducing capacity, thereby promoting cellular oxidative stress. In addition, it participates in regulating multiple signaling pathways as a member of the α-arrestin family of proteins. Accumulating evidence suggests that TXNIP is upregulated in diabetes and plays a pivotal role in the pathophysiological process of DR. In this review, we summarized the role of TXNIP in DRN, aiming to provide evidence for DR treatment in the future.

Advances in cell therapies using stem cells/progenitors as a novel approach for neurovascular repair of the diabetic retina

BACKGROUND

Diabetic retinopathy, a major complication of diabetes mellitus, is a leading cause of sigh-loss in working age adults. Progressive loss of integrity of the retinal neurovascular unit is a central element in the disease pathogenesis. Retinal ischemia and inflammatory processes drive interrelated pathologies such as blood retinal barrier disruption, fluid accumulation, gliosis, neuronal loss and/or aberrant neovascularisation. Current treatment options are somewhat limited to late-stages of the disease where there is already significant damage to the retinal architecture arising from degenerative, edematous and proliferative pathology. New preventive and interventional treatments to target early vasodegenerative and neurodegenerative stages of the disease are needed to ensure avoidance of sight-loss.

MAIN BODY

Historically, diabetic retinopathy has been considered a primarily microvascular disease of the retina and clinically it is classified based on the presence and severity of vascular lesions. It is now known that neurodegeneration plays a significant role during the pathogenesis. Loss of neurons has been documented at early stages in pre-clinical models as well as in individuals with diabetes and, in some, even prior to the onset of clinically overt diabetic retinopathy. Recent studies suggest that some patients have a primarily neurodegenerative phenotype. Retinal pigment epithelial cells and the choroid are also affected during the disease pathogenesis and these tissues may also need to be addressed by new regenerative treatments. Most stem cell research for diabetic retinopathy to date has focused on addressing vasculopathy. Pre-clinical and clinical studies aiming to restore damaged vasculature using vasoactive progenitors including mesenchymal stromal/stem cells, adipose stem cells, CD34+ cells, endothelial colony forming cells and induced pluripotent stem cell derived endothelial cells are discussed in this review. Stem cells that could replace dying neurons such as retinal progenitor cells, pluripotent stem cell derived photoreceptors and ganglion cells as well as Müller stem cells are also discussed. Finally, challenges of stem cell therapies relevant to diabetic retinopathy are considered.

CONCLUSION

Stem cell therapies hold great potential to replace dying cells during early and even late stages of diabetic retinopathy. However, due to the presence of different phenotypes, selecting the most suitable stem cell product for individual patients will be crucial for successful treatment.

An improved model of type 2 diabetes with effects on glucose tolerance, neuropathy and retinopathy with and without obesity

RATIONALE

Type 2 diabetes (T2D) costs billions of dollars annually, is also associated with pain (diabetic neuropathy), as well as retinopathy, lower urinary tract/urinary bladder dysfunction, depression, and systemic inflammation, affecting quality of life for patients. To that end, animal models are utilized to explore potential treatments, but may not reflect the complexity of the condition.

OBJECTIVE

We aimed to test an improved model of T2D that more closely mimics the clinical mechanisms and symptoms in an outbred strain of mouse.

FINDINGS

Male and female CD-1 mice (n = 72) were fed one of four diets: regular chow (REG), our Standard American Diet (SAD), a revised SAD (SAD2), or the commonly-used high-fat diet (HFD). Overall, HFD- and SAD-fed mice had significant weight gain and increased fat mass. Following injury, the SAD- and SAD2-fed mice showed protracted recovery, but the HFD-fed mice did not. Similarly, SAD- and SAD2-fed mice showed impaired retinal function compared to REG-fed mice, but the HFD-fed mice did not.

CONCLUSIONS

The SAD and SAD2 more closely model the problematic dietary intake and subsequent clinical symptoms associated with T2D.

POTENTIAL IMPACT OF STUDY

The adjusted SAD2 may be a better representation of a human-translatable diet than the SAD and HFD, and may allow for increased advances in the investigation of T2D-related symptoms.

ASSOCIATIONS BETWEEN DYSGLYCEMIA, RETINAL NEURODEGENERATION, AND MICROALBUMINURIA IN PREDIABETES AND TYPE 2 DIABETES

PURPOSE

To explore the association between retinal neurodegeneration and metabolic parameters in progressive dysglycemia.

METHOD

A cross-sectional study was performed on 68 participants: normal glucose tolerance (n = 23), prediabetes (n = 25), and Type 2 diabetes without diabetic retinopathy (n = 20). Anthropometric assessment and laboratory sampling for HbA1c, fasting glucose, insulin, c-peptide, lipid profile, renal function, and albumin-to-creatinine ratio were conducted. Central and pericentral macular thicknesses on spectral domain optical coherence tomography were compared with systemic parameters.

RESULTS

Baseline demographic characteristics were similar across all groups. Cuzick's trend test revealed progressive full-thickness macular thinning with increasing dysglycemia across all three groups (P = 0.015). The urinary albumin-to-creatinine ratio was significantly correlated with full-thickness superior (R = -0.435; P = 0.0002), inferior (R = -0.409; P = 0.0005), temporal (R = -0.429; P = 0.003), and nasal (R = -0.493; P < 0.0001) pericentral macular thinning, after post hoc Bonferroni adjustment. There was no association between macular thinning and waist circumference, body mass index, blood pressure, lipid profile, or insulin resistance.

CONCLUSION

Progressive dysglycemia is associated with macular thinning before the onset of visible retinopathy and occurs alongside microalbuminuria. Retinal neurodegenerative changes may help identify those most at risk from dysglycemic end-organ damage.

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.

Neurodegeneration of the cornea and retina in patients with type 1 diabetes without clinical evidence of diabetic retinopathy

AIM

Diabetic retinopathy (DR) is widely considered the earliest and most common microvascular complication of diabetes. However, recent studies have shown that retinal nerve fiber layer and corneal nerve abnormalities may be present in diabetic patients without retinopathy. This preliminary study aimed to establish if structural and functional changes in the nerve fiber layer of the retina and cornea occur in patients with type 1 diabetes (T1DM) without retinopathy.

METHODS

Twenty patients with T1DM, without clinical evidence of retinopathy (Age: 47.0 ± 2.5 years; Duration diabetes: 27.0 ± 3 years) and 15 age-matched healthy control subjects underwent detailed medical neurological examinations. Ophthalmic examinations using Spectral Domain Optical coherence tomography (SD-OCT), Standard Automated Perimetry (SAP), Flicker Defined Form High Edge Perimetry (FDF), Corneal Confocal Microscopy (CCM) and Non-contact corneal Aesthesiometry (NCCA) were performed to quantify the structure and function of the nerves in the retina and cornea, respectively.

RESULTS

At the structural level, retinal nerve fiber layer thickness (RNFL) was significantly reduced in the superior nasal (p=0.001) and inferior temporal (p=0.004) sectors, in diabetic patients. Retinal ganglion layer function was reduced in the patient group when assessed using Flicker Defined Form Perimetry (FDF), but this was not significant. The function of the cornea assessed by corneal sensitivity, using a non-contact corneal aesthesiometer (NCCA), was significantly reduced (p=0.001). Structural assessment of corneal nerves using corneal confocal microscopy (CCM) showed reduction at corneal nerve fiber density (CNFD) (p=0.01), branch density (CNBD) (p=0.006) and length (CNFL) (p=0.01) in patients with diabetes. Compared to control subjects, the percentage of abnormality in patients with T1DM for RNFL was 32% while the FDF was abnormal in 61% of patients. Corneal abnormality was observed in 47% for NCCA, 28% for CNFD, and 17% for CNFL. There was no correlation between neuronal damage in the retina and cornea.

CONCLUSIONS

Neuronal abnormalities were observed in both the retina and cornea of diabetic patients without evidence of retinopathy. The prevalence of structural and functional changes was higher in the retina compared to the cornea. This preliminary study suggests that structural neuronal changes may occur in parallel and correlate with functional changes. The assessment of corneal and retinal nerve structure may be clinically useful for detecting and monitoring the earliest stages of diabetic microvascular abnormalities.

Neurovascular Impairment and Therapeutic Strategies in Diabetic Retinopathy

Diabetic retinopathy has recently been defined as a highly specific neurovascular complication of diabetes. The chronic progression of the impairment of the interdependence of neurovascular units (NVUs) is associated with the pathogenesis of diabetic retinopathy. The NVUs consist of neurons, glial cells, and vascular cells, and the interdependent relationships between these cells are disturbed under diabetic conditions. Clinicians should understand and update the current knowledge of the neurovascular impairments in diabetic retinopathy. Above all, neuronal cell death is an irreversible change, and it is directly related to vision loss in patients with diabetic retinopathy. Thus, neuroprotective and vasoprotective therapies for diabetic retinopathy must be established. Understanding the physiological and pathological interdependence of the NVUs is helpful in establishing neuroprotective and vasoprotective therapies for diabetic retinopathy. This review focuses on the pathogenesis of the neurovascular impairments and introduces possible neurovascular protective therapies for diabetic retinopathy.

[Structural and microvascular changes in the retina and choroid in patients with chronic kidney disease]

PURPOSE

To study the main structural and microvascular changes in the retina and choroid in patients with diabetic retinopathy (DR) and chronic kidney disease (CKD), and their relationship with impaired renal function.

MATERIAL AND METHODS

The study included 158 patients (304 eyes). The 1^st group consisted of 50 patients with CKD (97 eyes); group 2 - 65 patients with DR (119 eyes), group 3 - 43 patients with CKD and DR (86 eyes). All study patients underwent complete ophthalmological examination, including optical coherence tomography (OCT) and OCT angiography (OCTA) of the macular region.

RESULTS

The analysis of structural parameters in groups of patients showed a decrease in the thickness of the ganglion cell layer and the inner plexiform layer of the retina in patients with DR (70.85±14.49 μm), with the lowest value in the CKD+DR group (65.84±15.34 μm) in comparison with the CKD group (75.64±10.32 μm). In the groups of patients with CKD, the thickness of the choroid (207.3±40.36 μm) was significantly reduced in comparison with the group of patients with DR (258.8±26.63 μm) and correlated with the stage of the disease. Patients in the CKD+DR group had the lowest perfusion and vascular density in the macular region (31.23±10.91% and 13.15±2.73 mm), an increase in the area and perimeter of the foveal avascular zone (0.55±0.26 mm², 3.30±0.84 mm). Pronounced correlations of decrease in choroidal thickness, vascular density, and perfusion volume with low glomerular filtration rate and CKD stage, as well as urea and creatinine levels were determined. An increase in the area of the foveal avascular zone correlated with lower retinal capillary density, decreased perfusion volume, and the stage of both DR and CKD.

CONCLUSION

Structural and hemodynamic disorders of the retina and choroid can be recognized as significant biomarkers for non-invasive diagnosis of microvascular complications of diabetes mellitus and impaired renal function.

Optical Coherence Tomography to Assess Neurodegeneration in Phenylalanine Hydroxylase Deficiency

In phenylalanine hydroxylase (PAH) deficiency, an easily feasible method to access the progression of neurodegeneration is warranted to contribute to current discussions on treatment indications and targets. The objective of the present study was to investigate whether optical coherence tomography (OCT) measures as markers of neurodegeneration differ between patients with PAH deficiency and healthy controls (HCs) according to phenotype and metabolic control. In this single-center cross-sectional study, 92 patients with different phenotypes of PAH deficiency [PAH deficiency not requiring treatment, early treated phenylketonuria (ETPKU), and late-diagnosed phenylketonuria (PKU)] compared with 76 HCs were examined using spectral-domain OCT. Indices of phenylalanine elevation and variability were correlated with OCT parameters. Late-diagnosed PKU patients showed reduced peripapillary retinal nerve fiber layer (pRNFL) thickness and combined ganglion cell and inner plexiform layer (GCIPL) volume. Adult ETPKU patients were found to have lower GCIPL volume (p = 0.016), which correlated with the indices of phenylalanine control. In pediatric ETPKU patients with poor metabolic control, pRNFL was significantly reduced (p = 0.004). Patients with PAH deficiency not requiring treatment did not exhibit retinal degeneration. Inner nuclear layer (INL) was significantly increased in the pediatric ETPKU patients, driven by those with current poor metabolic control (p = 0.006). Our data provide evidence of retinal neuroaxonal degeneration and INL swelling, depending on the phenotype, current age, and metabolic control. These findings suggest that OCT is suitable to investigate neurodegeneration in PKU and we propose OCT as a sensitive, reliable, safe, low-burden, and low-cost examination for future multicenter studies.

Interleaving Automatic Segmentation and Expert Opinion for Retinal Conditions

Optical coherence tomography (OCT) has become the leading diagnostic tool in modern ophthalmology. We are interested here in developing a support tool for the segmentation of retina layers. The proposed method relies on graph theory and geodesic distance. As each retina layer is characterised by different features, the proposed method interleaves various gradients during detection, such as horizontal and vertical gradients or open-closed gradients. The method was tested on a dataset of 750 OCT B-Scan Spectralis provided by the Ophthalmology Department of the County Emergency Hospital Cluj-Napoca. The method has smaller signed error on layers B1, B7 and B8, with the highest value of 0.43 pixels. The average value of signed error on all layers is −1.99 ± 1.14 px. The average value for mean absolute error is 2.60 ± 0.95 px. Since the target is a support tool for the human agent, the ophthalmologist can intervene after each automatic step. Human intervention includes validation or fine tuning of the automatic segmentation. In line with design criteria advocated by explainable artificial intelligence (XAI) and human-centered AI, this approach gives more control and transparency as well as more of a global perspective on the segmentation process.

Early neurovascular retinal changes detected by swept-source OCT in type 2 diabetes and association with diabetic kidney disease

Purpose

To evaluate retinal thickness and capillary density in patients with type 2 diabetes (T2D) and their association with diabetic kidney disease (DKD) using swept-source optical coherence tomography (SS-OCT).

Methods

A cross-sectional study was conducted with T2D patients with mild or no diabetic retinopathy (DR) and nondiabetic controls. Inner retinal layer thickness was measured with SS-OCT. Retinal capillary density and the foveal avascular zone (FAZ) were measured with SS-OCT angiography (OCTA). SS-OCT parameters were compared in patients with and without diabetic kidney disease (DKD) and nondiabetic controls.

Results

131 DKD eyes showed decreased ganglion cell layer plus (GCL+) (p = 0.005 TI; p = 0.022 I), retinal nerve fiber layer (RNFL) (p = 0.003), and central retinal thickness (CRT) (p = 0.032), as well as foveal avascular zone (FAZ) enlargement (p = 0.003) and lower capillary density in the superficial vascular plexus (p = 0.016, central quadrant), compared to controls. No statistically significant changes were found between diabetic patients without significant DKD and controls.

Conclusion

Our findings suggest early neurovascular damage in patients with T2D; these changes were more significant in patients with DKD. Larger longitudinal studies are warranted to determine the role of early neurovascular damage in the pathophysiology of severe DR.

Mbd2 deficiency alleviates retinal cell apoptosisvia the miR-345-5p/Atf1 axis in high glucoseinjury and streptozotocin-induced diabetic mice

DNA methylation is considered to play an important role in the development of diabetic retinopathy. Here, our goal was to investigate the precise role of methyl-CpG binding domain protein 2 (Mbd2) in the apoptosis of retinal ganglion cells (RGCs) in the early diabetic retina. Mbd2 was significantly upregulated after high glucose (HG) treatment and played a proapoptotic role in RGCs during HG-induced apoptosis. Combining ChIP and gene microarray datasets, the results showed that Mbd2 possessed potential binding sites for miR-345-5p, thereby elevating the expression levels of miR-345-5p via the enhancement of promoter demethylation. Activating transcription factor 1 (Atf1) played an anti-apoptotic role during the process of apoptosis in RGCs and acted as the target gene for miR-345-5p. Furthermore, the number of surviving RGCs in the diabetic retina was increased in Mbd2-knockout mice when compared with wild-type mice and the visual function became better accordingly. Collectively, our data demonstrated that the HG-induced overexpression of Mbd2 in the retina was partly responsible for the apoptosis of retinal neuronal cells through the miR-345-5p/Atf1 axis. Therefore, the targeting of Mbd2 might represent a novel therapeutic strategy for the treatment of neurodegeneration in the early diabetic retina.

Wide-field optical coherence tomography imaging in diabetic retinopathy

PURPOSE

To report the individual retinal layer thicknesses up to mid-equator in patients with diabetic retinopathy (DR) using Spectralis (Heidelberg Engineering, Heidelberg, Germany) wide-field optical coherence tomography (OCT).

METHODS

Retinal layers were segmented using a custom designed semi-automated algorithm, where reference points were marked by the examiner to enable software to automatically compute the thickness values of each retinal sublayer at an interval of 1 mm from reference points. The values of individual retinal thicknesses in eyes with varying severity of DR were compared with the values of healthy subjects. Generalized estimating equation was performed to compensate for inclusion of both eyes of patients.

RESULTS

A total of 64 patients (119 eyes) with a mean age of 68.97  ±  10.27 years were included. Overall, ganglion cell layer (GCL)/ inner plexiform layer (IPL) complex (-31.67 microns, p < 0.001), outer plexiform layer (-6.78 microns, p = 0.002) and photoreceptor layer (-22.90 microns, p < 0.001) showed significant thinning, while outer nuclear layer thickening ( + 68.19 microns, <0.001) was noted in eyes with DM compared to healthy subjects. Thickness changes were significantly more in the macular segment compared to nasal and temporal segments. GCL/ IPL complex and photoreceptor layers were found to be significantly thin in all grades of DR.

CONCLUSION

Retinal thicknesses vary significantly in patients with diabetic retinopathy and understanding patterns of these changes across different segments of the wide field OCT may help better elucidate the natural progression of the disease in terms of retinal anatomy.

Retinal neurodegeneration, macular circulation and morphology of the foveal avascular zone in diabetic patients: quantitative cross-sectional study using OCT-A

PURPOSE

Using OCT-A to investigate the association between neurodegeneration and vascular morphology in diabetic retinopathy (DR).

METHODS

Cross-sectional study. One hundred and sixty-two patients were enrolled and following fundoscopy were assigned to two groups according to DR severity: 54 patients to the group of no clinical signs of DR (noDR) and 54 to the non-proliferative DR (NPDR) group. Fifty-four age-matched patients without known diabetes were recruited as the control group. Patients underwent full ophthalmic examination followed by OCT-A. Central retinal thickness (CRT), vessel density (VD) in the superficial and deep retinal layers and foveal avascular zone (FAZ) area were measured. Additionally, ganglion cell complex (GCC) layer thickness along with global loss volume (GLV) and focal loss volume (FLV) indices was measured.

RESULTS

In total, 85 men with mean age of 51.93 ± 9.03 and 77 women with age of 50.14 ± 10.35 were examined. Mean diabetes duration was 4.62 ± 2.16 years in the noDR group and 11.34 ± 2.73 years in the NPDR group (p < 0.001). Superficial VD (sVD) and deep VD (dVD) were significantly different only between noDR and NPDR groups (p < 0.001 for both comparisons), but no statistically significant difference was observed between the controls and the DR groups. Global loss volume was significantly higher in the NPDR (4.38 ± 2.22) compared to the noDR group (3.24 ± 1.76; p < 0.03). Focal loss volume was significantly higher in both noDR (1.22 ± 1.03) and NPDR (2.09 ± 1.72) groups compared to controls (0.95 ± 0.83; p < 0.001 between noDR and NPDR and p = 0.02 between control and noDR groups). Significant associations were found between GLV and deep VD (p < 0.01, r = -0.48), FLV and superficial VD (p < 0.01, r = -0.42) and FLV with deep VD (p < 0.01, r = -0.64).

CONCLUSION

In this study, we evaluated the impact of DR in both the vascular layers and neural components of the retina as expressed by FAZ, sVD, dVD and GCC thickness, FLV and GLV using OCT-A. We found that FLV was significantly higher in both noDR and NPDR groups indicating that in progressive DR stages FLV values might be increased, which might serve as an early index of neuronal damage in patients with diabetes even in the absence of overt DR signs.

Joint segmentation of multi-class hyper-reflective foci in retinal optical coherence tomography images

Hyper-reflective foci (HRF) refers to the spot-shaped, block-shaped areas with characteristics of high local contrast and high reflectivity, which is mostly observed in retinal optical coherence tomography (OCT) images of patients with fundus diseases. HRF mainly appears hard exudates (HE) and microglia (MG) clinically. Accurate segmentation of HE and MG is essential to alleviate the harm in retinal diseases. However, it is still a challenge to segment HE and MG simultaneously due to similar pathological features, various shapes and location distribution, blurred boundaries, and small morphology dimensions. To tackle these problems, in this paper, we propose a novel global information fusion and dual decoder collaboration-based network (GD-Net), which can segment HE and MG in OCT images jointly. Specifically, to suppress the interference of similar pathological features, a novel global information fusion (GIF) module is proposed, which can aggregate the global semantic information efficiently. To further improve the segmentation performance, we design a dual decoder collaborative workspace (DDCW) to comprehensively utilize the semantic correlation between HE and MG while enhancing the mutual influence on them by feedback alternately. To further optimize GD-Net, we explore a joint loss function which integrates pixel-level with image-level. The dataset of this study comes from patients diagnosed with diabetic macular edema at the department of ophthalmology, University Medical Center Groningen, the Netherlands. Experimental results show that our proposed method performs better than other state-of-the-art methods, which suggests the effectiveness of the proposed method and provides research ideas for medical applications.