Association between retinal neuronal degeneration and visual function impairment in type 2 diabetic patients without diabetic retinopathy

Retinal microcirculation: A window into systemic circulation and metabolic disease

The retinal microcirculation system constitutes a unique terminal vessel bed of the systemic circulation, and its perfusion status is directly associated with the neural function of the retina. This vascular network, essential for nourishing various layers of the retina, comprises two primary microcirculation systems: the retinal microcirculation and the choroidal microcirculation, with each system supplying blood to distinct retinal layers and maintaining the associated neural function. The blood flow of those capillaries is regulated via different mechanisms. However, a range of internal and external factors can disrupt the normal architecture and blood flow within the retinal microcirculation, leading to several retinal pathologies, including diabetic retinopathy, macular edema, and vascular occlusions. Metabolic disturbances such as hyperglycemia, hypertension, and dyslipidemia are known to modify retinal microcirculation through various pathways. These alterations are observable in chronic metabolic conditions like diabetes, coronary artery disease, and cerebral microvascular disease due to advances in non-invasive or minimally invasive retinal imaging techniques. Thus, examination of the retinal microcirculation can provide insights into the progression of numerous chronic metabolic disorders. This review discusses the anatomy, physiology and pathophysiology of the retinal microvascular system, with a particular emphasis on the connections between retinal microcirculation and systemic circulation in both healthy states and in the context of prevalent chronic metabolic diseases.

Case series: Superficial plexus en face may aid distinction of retinal nerve fiber layer loss from diabetic retinal ischemia versus glaucoma

PURPOSE

This study aimed to demonstrate that the pattern and degree of capillary bed dropout in early glaucoma appear different on OCT-A superficial plexus en-face slabs compared with retinal ischemia. RNFL loss associated with retinal ischemia in diabetic patients may be explained and accounted for by overlying the RNFL deviation map on a superficial plexus en-face montage.

CASE REPORTS

Three middle-aged White men with diabetes mellitus showed cup-to-disc ratios of approximately 0.7 and RNFL and ganglion thinning. Each patient had several Cirrus OCT and OCT-A scans taken of the posterior pole. The OCT-A en-face images demonstrated specific patterns of superficial capillary dropout. The appearance of superficial plexus capillary dropout in one case of glaucoma is contrasted against two cases of retinal ischemia.

CONCLUSIONS

Early glaucoma appears to be associated with incomplete capillary bed dropout that extends from macular regions to the disc in a wedge- or arc-shaped pattern. Diabetic retinal ischemia appears to be associated with well-defined patchy and polygonal pockets of complete capillary bed obliteration that may not extend back to the disc. If an RNFL deviation map is superimposed over the superficial plexus en-face montage, areas of RNFL loss may correlate with and thus be well accounted for by areas of retinal ischemia in cases with RNFL thinning likely from ischemia. This approach may supplement inspection of OCT B-scans for focal retinal thinning when trying to differentiate RNFL and ganglion cell loss from retinal ischemia versus glaucoma in patients with diabetes. Formal research studies are needed to validate our observations and proposed use of OCT-A together with OCT in these patients.

Jin-Gui-Shen-Qi Wan ameliorates diabetic retinopathy by inhibiting apoptosis of retinal ganglion cells through the Akt/HIF-1α pathway

BACKGROUND

Jin-Gui-Shen-Qi Wan (JGSQ) has been used in China for thousands of years to treat various ailments, including frequent urination, blurred vision, and soreness in the waist and knees. It has traditional therapeutic advantages in improving eye diseases.

AIM OF THE STUDY

Clinical studies have confirmed the therapeutic efficacy of JGSQ in improving diabetes and vision; however, its efficacy and pharmacological effects in treating diabetic retinopathy (DR) remain unclear. Therefore, the aim of this study was to investigate the specific pharmacological effects and potential mechanisms of JGSQ in improving DR through a db/db model.

MATERIALS AND METHODS

db/db mice were given three different doses of orally administered JGSQ and metformin for 8 weeks, and then PAS staining of the retinal vascular network patch, transmission electron microscopy, H&E staining, and TUNEL staining were performed to determine the potential role of JGSQ in improving DR-induced neuronal cell apoptosis. Furthermore, network pharmacology analysis and molecular docking were carried out to identify the main potential targets of JGSQ, and the efficacy of JGSQ in improving DR was evaluated through western blotting and immunofluorescence staining, revealing its mechanism of action.

RESULTS

According to the results from H&E, TUNEL, and PAS staining of the retinal vascular network patch and transmission electron microscopy, JGSQ does not have an advantage in improving the abnormal morphology of vascular endothelial cells, but it has a significant effect on protecting retinal ganglion cells from apoptosis. Through network pharmacology and molecular docking, AKT, GAPDH, TNF, TP53, and IL-6 were identified as the main core targets of JGSQ. Subsequently, through western blot and immunofluorescence staining, it was found that JGSQ can inhibit HIF-1α, promote p-AKT expression, and inhibit TP53 expression. At the same time, inhibiting the release of inflammatory factors protects retinal ganglion cells and improves apoptosis in DR.

CONCLUSION

These results indicated that in the db/db DR mouse model, JGSQ can inhibit the expression of inflammatory cytokines and protect retinal ganglion cells from apoptosis, possibly by modulating the Akt/HIF-1α pathway.

New Insights on Dietary Polyphenols for the Management of Oxidative Stress and Neuroinflammation in Diabetic Retinopathy

Diabetic retinopathy (DR) is a neurodegenerative and vascular pathology that is considered one of the leading causes of blindness worldwide, resulting from complications of advanced diabetes mellitus (DM). Current therapies consist of protocols aiming to alleviate the existing clinical signs associated with microvascular alterations limited to the advanced disease stages. In response to the low resolution and limitations of the DR treatment, there is an urgent need to develop more effective alternative therapies to optimize glycemic, vascular, and neuronal parameters, including the reduction in the cellular damage promoted by inflammation and oxidative stress. Recent evidence has shown that dietary polyphenols reduce oxidative and inflammatory parameters of various diseases by modulating multiple cell signaling pathways and gene expression, contributing to the improvement of several chronic diseases, including metabolic and neurodegenerative diseases. However, despite the growing evidence for the bioactivities of phenolic compounds, there is still a lack of data, especially from human studies, on the therapeutic potential of these substances. This review aims to comprehensively describe and clarify the effects of dietary phenolic compounds on the pathophysiological mechanisms involved in DR, especially those of oxidative and inflammatory nature, through evidence from experimental studies. Finally, the review highlights the potential of dietary phenolic compounds as a prophylactic and therapeutic strategy and the need for further clinical studies approaching the efficacy of these substances in DR management.

Speckle Contrast as Retinal Tissue Integrity Biomarker in Patients with Type 1 Diabetes Mellitus with No Retinopathy

PURPOSE

To study the retinal and choroidal layers in type 1 diabetes mellitus (DM1) without diabetic retinopathy (DR), using speckle contrast of optical coherence tomography (OCT) images as a tissue biomarker in comparison with healthy subjects.

METHODS

OCT Spectralis images of 148 eyes, 84 from DM1 patients without DR signs, and 64 belonging to the control group, were collected. The speckle contrast and thickness of the inner retinal layer (IRL), the outer retinal layer (ORL), and the choroidal layer in the nasal parafoveal area (N3), were prospectively analyzed.

RESULTS

A statistically significant difference (p = 0.001) in the IRL thickness between groups was observed, being thicker in the DM1 group. There were no differences in the ORL and choroidal thicknesses between groups. A statistically significant difference (p = 0.02) in the IRL speckle contrast was obtained, being lower in the DM1 group. The maximum speckle contrast was reached in the ORL for both groups, although in the DM1 group, it occurs closer to the choroid, at 64 ± 8 μm (p = 0.008).

CONCLUSIONS

Statistically significant differences were found in speckle contrast and thickness between the control and the DM1 group, suggesting an IRL alteration of DM1 patients, supporting the retinal neurodegeneration before DR signs are observed.

Choroidal and Retinal Thicknesses in Type 2 Diabetes Mellitus with Moderate Diabetic Retinopathy Measured by Swept Source OCT

Background: To study choroidal thickness (CT) in type 2 diabetes mellitus (DM2) patients with moderate diabetic retinopathy (DR) and to correlate with changes in retinal thickness (RT) with swept-source OCT (SS-OCT) compared to healthy subjects. Methods: Fifty-four DM2 patients with moderate DR without diabetic macular edema (DME) and 73 age-matched healthy subjects were evaluated using SS-OCT to measure changes in total RT and CT in the nine areas of the Early Treatment Diabetic Retinopathy Study (ETDRS) macular grid. Results: The mean age was 64.06 ± 11.98 years and 60.79 ± 8.62 years in the diabetic and control groups, respectively. Total RT showed statistically significant differences in the temporal inner area, with higher values in the DM2 group (p = 0.010). CT did not show differences between the groups. There was a significant negative correlation between RT and age in all of the outer ETDRS areas and a positive significant correlation in the central area for the DM2 group. There was also a negative significant correlation between CT and age in all of the ETDRS areas except for the inferior inner area. In the DM2 group, a negative correlation was observed between RT and CT in the central area (p = 0.039) and in both horizontal parafoveal areas (temporal inner, p = 0.028; nasal inner, p= 0.003). Conclusion: DM2 patients with moderate DR have no changes with regard to CT. Both CT and RT decreased with age in DM2, showing a negative correlation between these factors in the central and horizontal parafoveal areas of the ETDRS grid.

Contrast Sensitivity Assessment in Early Diagnosis of Diabetic Retinopathy: A Systematic Review

INTRODUCTION

The purpose of this systematic review was to study whether contrast sensitivity assessment in people with diabetes could be a reliable test in early detection of diabetic retinopathy. A systematic search based on population, intervention, comparison, and outcome strategy was performed.

METHODS

PubMed, Scopus, and Web of Science were searched for English articles of human patients with type 1 and type 2 diabetes and contrast sensitivity measurements as domain studied.

RESULTS

Twentyone comparative cross-sectional studies were included. All of them showed significant loss of contrast sensitivity in people with diabetes and diabetic retinopathy regarding control patients of the same age, regardless of the method used. However, those without diabetic retinopathy, involve a loss of contrast sensitivity, although not always significant.

CONCLUSION

Changes in contrast sensitivity suggest that there is damage to the retina prior to the vascular ones and that they could be detected by this test.

Retinal neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy

In diabetes mellitus (DM) patients retinal complications were typically considered part of a vascular process. Recent research suggests that retinal degeneration in DM might also be caused by a neuropathy that could precede microvascular alterations. The present work reviews the currently available bibliography about neurodegeneration in patients with type 2 DM (DM2) without diabetic retinopathy (DR). In patients with non-severe, early DM2 without DR and good metabolic control visual function parameters show early abnormalities that precede clinical DR (in which we diagnose with a conventional ophthalmological examination). Using optical coherence tomography (OCT) technology, a reduction in macular and peripapillary thickness has been observed in different studies. Recent researches suggest that systemic complications (especially ischaemia) and a possible microvascular alteration eventually contributes to retinal neurodegeneration, which opens the door to new studies that include new techniques for evaluating the microvascularization of the retinal layers.

Retinal Vascularization Abnormalities Studied by Optical Coherence Tomography Angiography (OCTA) in Type 2 Diabetic Patients with Moderate Diabetic Retinopathy

Diabetic retinopathy (DR) is the most severe and frequent retinal vascular disease that causes significant visual loss on a global scale. The purpose of our study was to evaluate retinal vascularization in the superficial capillary plexus (SCP), the deep capillary plexus (DCP) and the choriocapillaris (CC) and changes in the foveal avascular zone (FAZ) by optical tomography angiography (OCTA) in patients with type 2 diabetes mellitus (DM2) with moderate DR but without diabetic macular oedema (DME). Fifty-four eyes of DM2 with moderate DR (level 43 in the ETDRS scale) and without DME and 73 age-matched healthy eyes were evaluated using OCTA with swept-source (SS)-OCT to measure microvascularization changes in SCP, DCP, CC and the FAZ. The mean ages were 64.06 ± 11.98 and 60.79 ± 8.62 years in the DM2 and control groups, respectively. Visual acuity (VA) was lower in the DM2 patients (p = 0.001), OCTA showed changes in the SCP with a significant diminution in the vascular density and the FAZ area was significantly higher compared to healthy controls, with p < 0.001 at the SCP level. The most prevalent anatomical alterations were peripheral disruption in the SCP (83.3%), microaneurysms (MA) in the SCP and in the DCP (79.6% and 79.6%, respectively) and flow changes in the DCP (81.5%). A significant positive correlation was observed between the DM2 duration and the FAZ area in the SCP (0.304 with p = 0.025). A significant negative correlation was also found between age and CC central perfusion (p < 0.001). In summary, a decrease in the vascular density in DM2 patients with moderate DR without DME was observed, especially at the retinal SPC level. Furthermore, it was found that the FAZ was increased in the DM2 group in both retinal plexuses and was greater in the SCP group.

Changes in retinal layers in type 1 diabetes mellitus without retinopathy measured by spectral domain and swept source OCTs

To evaluate changes in inner retinal layer (IRL) thicknesses in patients with type 1 diabetes mellitus (DM1) with no diabetic retinopathy (DR) using two different optical coherence tomography (OCT) devices. Ninety DM1 and 60 healthy eyes were evaluated using spectral domain (SD)-OCT and swept source (SS)-OCT to measure changes in the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and inner nuclear layer (INL) thicknesses in all Early Treatment of Diabetic Retinopathy Study (ETDRS) macular areas. Functional tests were performed in both groups, including ETDRS with 100, 2.5 and 1.25% contrast, and color vision. The mean ages were 42.93 ± 13.62 and 41.52 ± 13.05 years in the diabetic and control groups, respectively. Visual acuity (VA) with ETDRS 1.25% was lower in the DM1 patients. Both ETDRS 2.5% and color vision were lower in the DM1 group but did not reach statistical significance. Retinal thicknesses in the central area and in the vertical outer areas were higher in the DM1 group. Differences were found in the IRL with no changes in the outer ones. Long-term DM1 patients with no DR maintained visual function, with a decrease in VA with 1.25% ETDRS contrast. Macular thickness measurements were higher using Spectralis SD-OCT than DRI Triton SS-OCT, and DM1 patients had a decrease in IRL thickness, especially in the GCL at the parafoveal level, generating thinning of the RNFL in the peripheral areas. There were no differences in outer retinal layer (ORL) thickness.

Microperimetry and Optical Coherence Tomography Changes in Type-1 Diabetes Mellitus without Retinopathy

Background: We aimed to measure and correlate inner retinal layer (IRL) thickness and macular sensitivity by optical coherence tomography (OCT) and by microperimetry, respectively, in type 1 diabetes mellitus patients (DM1) without diabetic retinopathy (DR). Methods: Fifty-one DM1 patients and 81 age-matched healthy subjects underwent measurement of the axial length (AL), retinal thickness in the macular ETDRS areas by swept source (SS)-OCT and macular sensitivity by microperimeter. Results: The total retinal and IRL thicknesses were thicker in the DM1 group (p < 0.05) in practically all ETDRS areas, and they had a generalized decrease in sensitivity (p < 0.05) in 9 areas between both groups. There was a significant negative correlation between retinal sensitivity and age in all areas and in visual acuity (VA) in 5 out of the 9 areas for DM1 patients. Only a mild negative correlation was observed between retinal sensitivity in the 5° nasal inner (5NI) area and in IRL thickness in the temporal inner (TI) area (−0.309 with p = 0.029) in the DM1 group. Conclusion: Aging and disease evolution in DM1 patients without DR signs generate a decrease in retinal sensitivity. There was a direct relationship between retinal sensitivity and macular thickness in the DM1 group.

ANATOMICAL AND FUNCTIONAL TESTING IN DIABETIC PATIENTS WITHOUT RETINOPATHY: Results of Optical Coherence Tomography Angiography and Visual Acuity Under Varying Contrast and Luminance Conditions

PURPOSE

To assess early retinal microvascular and functional changes in diabetic patients without clinical evidence of diabetic retinopathy with optical coherence tomography angiography and central visual analyzer.

METHODS

This was an observational case-control study of diabetic patients without diabetic retinopathy and nondiabetic controls. Patients underwent optical coherence tomography angiography imaging and visual acuity testing using the central visual analyzer. The foveal avascular zone area and the capillary density in the superficial and deep capillary plexuses were measured manually by a masked grader.

RESULTS

Sixty eyes from 35 diabetic patients were included in the study group, and 45 eyes from 31 nondiabetic patients were included in the control group. The foveal avascular zone area was not significantly different between the diabetic group and controls (both P > 0.05). The mean capillary density in the deep capillary plexus was significantly lower in diabetic eyes compared with control eyes (P = 0.04). The mean visual acuity in all central visual analyzer modules was significantly decreased in diabetic patients compared with controls (all P < 0.05).

CONCLUSION

Optical coherence tomography angiography was able to detect retinal microvascular changes in the deep capillary plexus, and the central visual analyzer showed signs of decreased visual acuity under conditions simulating suboptimal contrast and glare in diabetic patients without diabetic retinopathy.

A critical review: Psychophysical assessments of diabetic retinopathy

Diabetic retinal disease remains a leading cause of vision loss despite currently available screening methods, ocular treatments, and efforts to control metabolic dysfunction. It is now understood that diabetes damages the entire retina and the cellular components of the neurovascular unit. Multiple studies have demonstrated impairment of various aspects of retinal function across the spectrum of retinopathy severity. Here we review these tests, the principles underlying their use, clinical data from multiple publications, the strengths and limitations of the studies, and prospects for their application to understand the pathophysiology of diabetic retinal disease and monitor its response to therapy. We focus on visual acuity, contrast sensitivity, color vision, visual field, and dark adaptation and their use to understand the pathophysiology of diabetic retinopathy and as potential endpoints for clinical trials.

Neuroinflammation and oxidative stress act in concert to promote neurodegeneration in the diabetic retina and optic nerve: galectin-3 participation

Diabetes is a lifelong disease characterized by glucose metabolic imbalance, in which low insulin levels or impaired insulin signaling lead to hyperglycemic state. Within 20 years of diabetes progression, 95% of patients will have diabetic retinopathy, the leading cause of visual defects in working-age people worldwide. Although diabetes is considered a microvascular disease, recent studies have shown that neurodegeneration precedes vascular changes within the diabetic visual system, albeit its mechanisms are still under investigation. Neuroinflammation and oxidative stress are intrinsically related phenomena, since macrophage/microglia and astrocytes are the main sources of reactive oxygen species during central nervous system chronic degenerative diseases, and both pathological processes are increased in the visual system during diabetes. The present review will focus on recent findings of the contribution of oxidative stress derived from neuroinflammation in the early neurodegenerative aspects of the diabetic visual system and their relationship with galectin-3.

Ability of Swept source OCT technology to detect neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy

PURPOSE

To evaluate neurodegeneration in patients with type 2 Diabetes Mellitus (DM2) without diabetic retinopathy, and to assess the possible role of chronic systemic ischaemia and disease duration in retinal changes.

STUDY DESIGN

Observational cross sectional study.

METHODS

Sixty eyes of 60 patients with DM2 without signs of diabetic retinopathy (DR), and 60 eyes of 60 healthy controls underwent retinal (ganglion cell layer (GCL), and retinal nerve fiber layer (RNFL) and choroidal evaluation using Swept source Optical coherence tomography, which allows high quality analysis of the different retinal layers and the choroidal plexus. Comparison between patients with presence/absence of systemic vascular complications and different disease duration time was performed.

RESULTS

Macular GCL and RNFL were reduced in patients compared to controls (p < 0.001). In the peripapillary area, a reduction of the RNFL (p < 0.001) was observed in patients with DM2. There were no significant changes observed in the choroidal plexus of these patients. Patients with systemic ischaemia presented significant thinning of the choroid and further reduction of the temporal RNFL (p = 0.014) and GCL (p = 0.016) thickness. The GCL and the choroid were also thinner in patients with longer disease duration.

CONCLUSIONS

Patients with early DM2 present retinal neurodegeneration prior to the appearance of clinically observable vascular retinal changes. In these patients chronic systemic ischaemia caused reduction of the choroidal plexus and further damage to the retinal layers, adding new information on systemic chronic ischaemia and retinal neurodegeneration in patients with DM2 without DR.

[Neurodegenerative changes of the retina in patients with diabetes]

PURPOSE

To investigate the morphological and functional state of the outer and inner layers of the retina in patients with diabetes mellitus (DM) and nonproliferative diabetic retinopathy (NPDR), to determine the presence and nature of the relationships between structural and functional changes.

MATERIAL AND METHODS

The study included 50 patients with subcompensated diabetes and NPDR and 40 people from the control group (healthy). All patients underwent OCT of the retina and optic nerve using RTVue-100 apparatus (Optovue, USA), as well as multifocal electroretinography (mfERG) and pattern electroretinography (PERG) on EP-1000 Multifocal device ('Tomey GmbH', Germany).

RESULTS

When analyzing the results of OCT in patients with NPDR, a decrease in the total thickness of the retina and the thickness of its inner layers in the fovea and parafovea regions was found in comparison with the control group (p<0.001), thinning of the retinal ganglion cell (GCS) complex with increased focal losses (FLV) of up to 1.4% (Mann-Whitney test, p=0.001). In the group of patients with diabetes, there was a statistically significant decrease in the density and amplitude of P1 mfERG in all five 'rings' (Mann-Whitney test, p<0.001), increase in implicit time in the first 3 rings, decrease in P50 and N95 amplitude, increase in implicit time of N95 PERG (p=0.001) compared to the control group.

CONCLUSION

The study revealed changes in the structure and functioning of the outer and inner layers of the retina in patients with NPDR, and established a reliable correlation between the morphological parameters (according to the OCT) and electrophysiological parameters (according to the mfERG and PERG data).

Neurodegeneration in Patients with Type 2 Diabetes Mellitus without Diabetic Retinopathy

Purpose

To evaluate neurodegeneration in patients with type 2 diabetes mellitus (DM2) without diabetic retinopathy and to assess the possible role of systemic vascular complications in retinal changes.

Methods

Sixty eyes of 60 patients with DM2 and without any signs of diabetic retinopathy and 60 eyes of 60 healthy controls underwent retinal evaluation using Spectralis optical coherence tomography. Macular ganglion cell layer (GCL) and retinal nerve fiber layer (RNFL) were evaluated. Peripapillary RNFL thickness was assessed using Glaucoma and Axonal Analytics applications. Comparison between patients with the presence/absence of systemic vascular complications and different disease duration was made.

Results

Macular GCL was reduced in patients compared to controls (p < 0.001). Differences in the macular RNFL thickness were only observed in the outer inferior sector (p=0.033). A reduction in the peripapillary RNFL (average, inferior, and inferotemporal thickness, p < 0.05 for all three) was observed in patients using both applications. Patients with chronic systemic vascular complications presented a reduction in the temporal RNFL (p=0.019) compared to patients without complications. The superotemporal RNFL thickness was thinner in patients with longer disease duration.

Conclusions

Patients with type 2 DM without diabetic retinopathy and good metabolic control present neurodegeneration affecting neurons in the macular area and axons in different sectors of the optic disc. Systemic vascular complications contributed to further axonal damage in these patients, suggesting a possible role of subclinical ischaemia to retinal neurodegeneration in type 2 DM.

Retinal Neurodegeneration as an Early Manifestation of Diabetic Eye Disease and Potential Neuroprotective Therapies

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a major cause of visual impairment and blindness throughout the world. Microvascular changes have long been regarded central to disease pathogenesis. In recent years, however, retinal neurodegeneration is increasingly being hypothesized to occur prior to the vascular changes classically associated with DR and contribute to disease pathogenesis.

RECENT FINDINGS

There is growing structural and functional evidence from human and animal studies that suggests retinal neurodegeneration to be an early component of DR. Identification of new therapeutic targets is an ongoing area of research with several different molecules undergoing testing in animal models for their neuroprotective properties and for possible use in humans. Retinal neurodegeneration may play a central role in DR pathogenesis. As new therapies are developed, it will be important to develop criteria for clinically defining retinal neurodegeneration. A standardization of the methods for monitoring neurodegeneration along with more sensitive means of detecting preclinical damage is also needed.

Clinical Decision-Making when Treating Diabetic Macular Edema Patients with Dexamethasone Intravitreal Implants

Diabetes mellitus (DM) is a metabolic disease frequently associated with comorbidities that include diabetic macular edema (DME). The current medical approach to treating DME involves intravitreal injections with either anti-vascular endothelial growth factors or steroids. However, the burden associated with intravitreal injections and DM-derived complications is high, underlining the need to find optimal treatment regimens. In this article we describe the considerations we apply when treating DME patients with dexamethasone intravitreal implants (Ozurdex®), particularly those that influence the clinical decision-making process during the follow-up period. These considerations are based both on the available medical literature and on our clinical experience following the use of these implants in this type of patient, the goal being to optimize the number of injections and the clinical outcome of this therapy. We also provide a general overview of the pathophysiology of DME, highlighting the inflammatory component as a rationale to use steroids in these patients.

The Role of Microglia in Diabetic Retinopathy: Inflammation, Microvasculature Defects and Neurodegeneration

Diabetic retinopathy is a common complication of diabetes mellitus, which appears in one third of all diabetic patients and is a prominent cause of vision loss. First discovered as a microvascular disease, intensive research in the field identified inflammation and neurodegeneration to be part of diabetic retinopathy. Microglia, the resident monocytes of the retina, are activated due to a complex interplay between the different cell types of the retina and diverse pathological pathways. The trigger for developing diabetic retinopathy is diabetes-induced hyperglycemia, accompanied by leukostasis and vascular leakages. Transcriptional changes in activated microglia, mediated via the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) and extracellular signal–regulated kinase (ERK) signaling pathways, results in release of various pro-inflammatory mediators, including cytokines, chemokines, caspases and glutamate. Activated microglia additionally increased proliferation and migration. Among other consequences, these changes in microglia severely affected retinal neurons, causing increased apoptosis and subsequent thinning of the nerve fiber layer, resulting in visual loss. New potential therapeutics need to interfere with these diabetic complications even before changes in the retina are diagnosed, to prevent neuronal apoptosis and blindness in patients.

Structural neurodegeneration correlates with early diabetic retinopathy

PURPOSE

To examine differences in structural and functional neurodegenerative measurements between patients with no and early diabetic retinopathy (DR).

METHODS

In this cross-sectional study, we examined 103 patients with type 2 diabetes mellitus. In 7-field fundus photographs acquired with Topcon TRC-NW6S, a single, certified grader determined the presence of DR according to the Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Retinal neurodegeneration was evaluated by Topcon 3D OCT-2000 spectral domain optical coherence tomography (OCT) and by a RETI-scan multifocal electroretinography (mf-ERG) system in rings 1-6.

RESULTS

Median age and duration of diabetes were 63.6 and 10 years, respectively, and 46% were men. Median HbA1c was 50 mmol/mol (6.7%), and ETDRS levels were 10 (41.7%, n = 43), 20 (35.0%, n = 36), and 35 (23.3%, n = 24). The duration of diabetes increased with higher levels of DR (p = 0.04), but patients with different level of DR did not differ according to age, sex, blood pressure, HbA1c, and mf-ERG or OCT parameters. In a multiple logistic regression model, macular ganglion cell layer thickness was associated with the presence of DR (OR 1.73 per 5 μm increase, 95% CI 1.06-2.85, p = 0.03). Conversely, retinal nerve fibre layer thickness at optic disc was inversely related to DR (OR 0.69 per 5 μm increase, 95% CI 0.51-0.95, p = 0.02). There were no associations between DR and mf-ERG outcomes.

CONCLUSION

In patients with type 2 diabetes, structural neurogenic characteristics were associated with DR. If confirmed by larger prospective studies, these results may indicate that a complex neurovascular interaction is an early event in the pathogenesis of DR.

The prevalence of visual impairment and blindness in underserved rural areas: a crucial issue for future

PurposeTo determine the prevalence of visual impairment and blindness in underserved Iranian villages and to identify the most common cause of visual impairment and blindness.Patients and methodsMultistage cluster sampling was used to select the participants who were then invited to undergo complete examinations. Optometric examinations including visual acuity, and refraction were performed for all individuals. Ophthalmic examinations included slit-lamp biomicroscopy and ophthalmoscopy. Visual impairment was determined according to the definitions of the WHO and presenting vision.ResultsOf 3851 selected individuals, 3314 (86.5%) participated in the study. After using the exclusion criteria, the present report was prepared based on the data of 3095 participants. The mean age of the participants was 37.6±20.7 years (3-93 years). The prevalence of visual impairment and blindness was 6.43% (95% confidence interval (CI): 3.71-9.14) and 1.18% (95% CI: 0.56-1.79), respectively. The prevalence of visual impairment varied from 0.75% in participants aged less than 5 years to 38.36% in individuals above the age of 70 years. Uncorrected refractive errors and cataract were the first and second leading causes of visual impairment; moreover, cataract and refractive errors were responsible for 35.90 and 20.51% of the cases of blindness, respectively.ConclusionThe prevalence of visual impairment was markedly high in this study. Lack of access to health services was the main reason for the high prevalence of visual impairment in this study. Cataract and refractive errors are responsible for 80% of visual impairments which can be due to poverty in underserved villages.

Retinal ganglion cell complex changes using spectral domain optical coherence tomography in diabetic patients without retinopathy

AIM

To assess the ganglion cell complex (GCC) thickness in diabetic eyes without retinopathy.

METHODS

Two groups included 45 diabetic eyes without retinopathy and 21 non diabetic eyes. All subjects underwent full medical and ophthalmological history, full ophthalmological examination, measuring GCC thickness and central foveal thickness (CFT) using the RTVue^® spectral domain-optical coherence tomography (SD-OCT), and HbA1C level.

RESULTS

GCC focal loss volume (FLV%) was significantly more in diabetic eyes (22.2% below normal) than normal eyes (P=0.024). No statistically significant difference was found between the diabetic group and the control group regarding GCC global loss volume (GLV%) (P=0.160). CFT was positively correlated to the average, superior and inferior GCC (P=0.001, 0.000 and 0.001 respectively) and negatively correlated to GLV% and FLV% (P=0.002 and 0.031 respectively) in diabetic eyes. C/D ratio in diabetic eyes was negatively correlated to average, superior and inferior GCC (P=0.015, 0.007 and 0.017 respectively). The FLV% was negatively correlated to the refraction and level of HbA1c (P=0.019 and 0.013 respectively) and positively correlated to the best corrected visual acuity (BCVA) in logMAR in diabetic group (P=0.004).

CONCLUSION

Significant GCC thinning in diabetes predates retinal vasculopathy, which is mainly focal rather than diffuse. It has no preference to either the superior or inferior halves of the macula. Increase of myopic error is significantly accompanied with increased focal GCC loss. GCC loss is accompanied with increased C/D ratio in diabetic eyes.