Diabetic Macular Edema: Pathophysiology and Novel Therapeutic Targets

Diabetic macular edema in proliferative stage treated with anti-vascular endothelial growth factor agent and triamcinolone acetonide by laser-based strategies

AIM

To appraise the effect of treatment for diabetic macular edema (DME) in proliferative stage with sufficient panrentinal photocoagulation (PRP) therapy and intravitreal injections (IV) Conbercept and posterior subtenon's triamcinolone acetonide (STTA) sequential therapy.

METHODS

This prospective clinical randomized controlled trial of cross-over design was conducted in three phases. The participants included cases of DME in proliferative stage. They were divided into two groups and treated with PRP before enrollment. Group A were treated with IV-Conbercept 0.5 mg for one month in the 1^st phase. Group B were treated with STTA 40 mg (twice per two weeks). The interventions were exchanged in the second phase (2mo) between the two groups. In the third phase (3-6mo) no other treatment was given. Best corrected visual acuity (BCVA), central macular thickness (CMT) measured by OCT and complications were compared.

RESULTS

After phase I: in Group A, BCVA improved from 0.201±0.17 to 0.37±0.24 (F=5.88, P=0.004). CMT changed from 449±155.10 to 304.1±84.70 µm (F=14.9, P<0.01). In Group B, BCVA changed from 0.195±0.19 to 0.26±0.20 (F=0.76, P=0.41) while CMT changed from 463.82±152.92 to 366.00±115.40 µm (F=3.70, P<0.03). The improvement of BCVA was better in Group A (P<0.05). After phase II: in Group A, BCVA raised to 0.47±0.27 (F=0.26, P<0.01), CMT reduced to 260.67±62.97 µm (F=-188.3, P<0.01); in Group B, BCVA raised to 0.51±0.26 (F=0.31, P<0.01), CMT reduced to 261.93±50.15 µm (F=-201.9, P<0.01). But there were no difference between two groups (P>0.05). After phase III: in Group A, BCVA maintained 0.42±0.25 (F=0.22, P=0.001), CMT maintained 267.8±58.34 µm, (F=-0.27, P<0.01); in Group B, BCVA was 0.47±0.25 (F=-0.27, P<0.01), CMT was 272.71±49.16 µm (F=-191.1, P<0.01). No serious complications happened in all phases.

CONCLUSION

PRP+Conbercept is better than PRP+STTA in DME with proliferative stage but PRP+Conbercept+STTA sequential therapy may be a wiser choice for persistent effectiveness on anatomical as well as functional status.

Safety and Feasibility of Quantitative Multiplexed Cytokine Analysis From Office-Based Vitreous Aspiration

Purpose

The goals of this study were to evaluate the safety of office-based vitreous sampling, and determine the utility of these samples with multiplex cytokine analysis.

Methods

Vitreous samples were collected from office-based needle aspiration and the rate of adverse events during follow-up was reviewed. The vitreous cytokine concentrations in a subset of patients with diabetic macular edema (DME) were analyzed using a 42 plex-cytokine bead array. These results were compared with vitreous cytokine concentrations in proliferative diabetic retinopathy (PDR) and controls (macular hole, epiretinal membrane, symptomatic vitreous floaters) from pars plana vitrectomy.

Results

An adequate volume of vitreous fluid (100–200 μL) was obtained in 52 (88%) of 59 office-based sampling attempts. The average length of follow-up was 300 days (range, 42–926 days). There were no complications, including cataract, retinal tear or detachment, and endophthalmitis. Two patients (3%) had posterior vitreous detachments within 3 months. Vitreous cytokine concentrations were measured in 44 patients: 14 controls, 13 with DME, and 17 with PDR. The concentration of ADAM11, CXCL-10, IL-8, and PDGF-A were higher in PDR compared with controls and DME. The concentration of IL-6 was higher in PDR compared with controls, but not compared with DME.

Conclusions

Office-based vitreous aspiration is safe and yields high-quality samples for multiplex vitreous cytokine analysis. Significant elevations of vitreous cytokines were found in PDR compared with DME and controls, including the novel finding of elevated ADAM11. As such, office-based aspiration is a safe and effective means to identify vitreous factors associated with vitreoretinal disease.

Visualization of changes in the foveal avascular zone in both observed and treated diabetic macular edema using optical coherence tomography angiography

BACKGROUND

Central vision loss in diabetic retinopathy is commonly related to diabetic macular edema (DME). The objective of this study was to describe changes between consecutive visits on optical coherence tomography angiography (OCTA) of the foveal avascular zone (FAZ) in eyes with DME.

METHODS

20 eyes from 14 patients with DME were imaged on 2 successive clinic visits separated by at least 1 month. The mean interval between visits was 3.2 months. The only intervention used was intravitreal anti-VEGF in 11 eyes; the others were observed over time without treatment. Two different readers measured FAZ area using a pseudo-automated tool in comparison to a manual tracing tool. Qualitative changes in the appearance of the vasculature surrounding the FAZ were also recorded. The retinal capillary plexus was segmented into deep and superficial plexuses, and FAZ measurements were done on the superficial, deep, and summated plexuses.

RESULTS

Pseudo-automated and manual measurements of FAZ area decreased significantly (p < 0.05) between visits in the deep, superficial, and summated plexuses. Qualitative analysis of vasculature surrounding the FAZ showed that most of the vascular changes (65%) over time were visible in the deep plexus, compared to 30 and 20% in the superficial and summated plexuses, respectively.

CONCLUSIONS

The most significant differences in FAZ size over time were in the summated plexus (p < 0.001), while changes in FAZ appearance were most prominent in the deep plexus. Absolute decrease in FAZ size over visits was largest in the deep plexus. Our results demonstrate that OCTA can effectively be used to measure FAZ area in patients with DME, visualize qualitative changes in retinal vasculature, and visualize the segmentation levels at which these changes can be best appreciated. However, larger studies are needed to evaluate the reproducibility of manual and pseudo-automated measuring techniques.

Diabetic retinopathy and dysregulated innate immunity

Diabetic retinopathy (DR) is the progressive degeneration of retinal blood vessels and neurons. Inflammation is known to play an important role in the pathogenesis of DR. During diabetes, metabolic disorder leads to the release of damage-associated molecular patterns (DAMPs) both in the retina and elsewhere in the body. The innate immune system provides the first line of defense against the DAMPs. In the early stages of DR when the blood retinal barrier (BRB) is intact, retinal microglia and the complement system are activated at low levels. This low-level of inflammation (para-inflammation) is believed to be essential to maintain homeostasis and restore functionality. However, prolonged stimulation by DAMPs in the diabetic eye leads to maladaptation of the innate immune system and dysregulated para-inflammation may contribute to DR development. In the advanced stages of DR where immune privilege is comprised, circulating immune cells and serum proteins may infiltrate the retina and participate in retinal chronic inflammation and retinal vascular and neuronal damage. This review discusses how the innate immune system is activated in diabetes and DR. The view also discusses why the protective immune response becomes detrimental in DR.

Diabetic macular oedema: clinical risk factors and emerging genetic influences

Diabetic macular oedema is the major cause of visual impairment in type 1 and type 2 diabetes. As type 2 diabetes becomes more prevalent worldwide, the prevalence of diabetic macular oedema is also expected to rise. Current management of diabetic macular oedema is challenging, expensive and not optimal in a subset of patients. Therefore, it is important to increase our understanding of the risk factors involved and develop preventative strategies. While clinical risk factors for diabetic macular oedema have been identified, few studies have addressed potential genetic risk factors. Epidemiology and family studies suggest genetic influences are of importance. In this review, we summarise known clinical risk factors, as well as discuss the small number of genetic studies that have been performed for diabetic macular oedema.

Fluocinolone Acetonide Intravitreal Implant 0.19 mg (ILUVIEN®): A Review in Diabetic Macular Edema

Fluocinolone acetonide intravitreal implant 0.19 mg (ILUVIEN^®) is a nonbiodegradable, injectable, corticosteroid implant that is approved in several countries, including the USA, for the treatment of diabetic macular edema (DME). ILUVIEN^® releases fluocinolone acetonide at an initial rate of 0.25 µg/day (average rate 0.2 µg/day) and lasts 36 months. In the two pooled pivotal FAME trials in patients with DME previously treated with macular laser photocoagulation, fluocinolone acetonide intravitreal implant 0.2 µg/day was significantly more effective than sham injection with respect to the proportion of patients with an improvement from baseline in best-corrected visual acuity of ≥15 letters at 24 months (primary endpoint). This therapeutic effect was maintained at 36 months. The implant also significantly decreased foveal thickness at 24 months. FAME study results are broadly supported by real-world studies in patients with chronic DME considered insufficiently responsive to available therapies. Consistent with corticosteroid class-specific adverse events, cataract and elevated intraocular pressure (IOP) were the most common adverse events with the fluocinolone acetonide intravitreal implant. Raised IOP was treated with medications in most patients, with <5% requiring incisional IOP-lowering surgery. In the USA, fluocinolone acetonide intravitreal implant should be used only in patients who have been previously treated with a course of corticosteroids and did not have a clinically significant increase in IOP. Available data indicate that fluocinolone acetonide intravitreal implant 0.19 mg is a useful option for the treatment of DME in these patients.

Retinal neurodegeneration in patients with type 1 diabetes mellitus: the role of glycemic variability

AIMS

Recent studies have identified neuroretinal abnormalities in persons affected by diabetes mellitus, before the onset of microvascular alterations. However, the role of glycemic variability (GV) on early retinal neurodegeneration is still not clarified.

METHODS

To explore the relationship between glycemic control and neuroretinal characteristics, 37 persons with Type 1 diabetes mellitus (Type 1 DM) divided into two groups with no signs (noRD) and with mild non-proliferative diabetic retinopathy (NPDR) compared to 13 healthy control participants (C) were recruited. All persons underwent an optical coherence tomography with automatic segmentation of all neuroretinal layers. Measurements of mean of nasal (N)/temporal (T)/superior (S)/inferior (I) macular quadrants for individual layer were also calculated. Metabolic control was evaluated by glycated hemoglobin (HbA1c), and indexes of GV were calculated from continuous glucose monitoring.

RESULTS

The difference among the three groups in terms of RNFL thickness was significantly dependent on quadrant (F(6;132) = 2.315; p = 0.037). This interaction was due to a specific difference in RNFL-N thickness, where both Type 1 DM groups showed a similar reduction versus C (-3.9 for noDR and -4.9 for NPDR), without any relevant difference between them (-1.0). Inner nuclear layer (INL) was increased in all quadrants in the two Type 1 DM groups compared to C (mean difference = 7.73; 95% CI: 0.32-15.14, p = 0.043; mean difference = 7.74; 95% CI: 0.33-15.15, p = 0.043, respectively). A negative correlation between RNFL-N and low blood glucose index (r = -0.382, p = 0.034) and positive correlation between INL and continuous overall net glycemic action -1, -2, -4 h (r = 0.40, p = 0.025; r = 0.39, p = 0.031; r = 0.41, p = 0.021, respectively) were observed in Type 1 DM patients. The triglycerides were positively and significantly correlated to INL (r = 0.48, p = 0.011), in Type 1 DM subjects. GV and triglycerides resulted both independent predictors of increased INL thickness. No correlation was found with HbA1c.

CONCLUSIONS

Early structural damage of neuroretina in persons with Type 1 DM patients is related to glucose fluctuations. GV should be addressed, even in the presence of a good metabolic control.

Opening eyes to nanomedicine: Where we are, challenges and expectations on nanotherapy for diabetic retinopathy

People affected with ocular diseases will significantly increase over the next decades, and, consequently, a substantial increase in health costs is expected. Diabetic retinopathy is the most common chronic complication of diabetes. The treatment of eye diseases affecting the posterior segment, such as diabetic retinopathy, is quite challenging due to the anatomy, physiology and biochemistry of the eye. Therefore, the development of new therapeutics for posterior eye diseases has been a major focus of pharmaceutical research in the area of vision sciences. Several nanosystems already offer efficient solutions for ophthalmological conditions, targeting internal eye tissues, as the retina, and many novel products are expected to appear hereafter. This review provides an insight on nanoparticle-based solutions for therapies directed to posterior segment of the eye diseases, particularly diabetic retinopathy, the present scenario, and the demands and expectations for the future.

RETINAL VASCULAR CYSTOID MACULAR EDEMA: Review and New Theory

: Retinal vascular disease has the potential to affect hundreds of millions of people, with the inherent risk of vision loss related to cystoid macular edema. Although there have been histologic evaluation of eyes having cystoid macular edema, the most recent paper was published more than 30 years ago. In retinal vascular cystoid macular edema fluorescein angiography, a modality that images the superficial vascular plexus, shows increased leakage. Optical coherence tomography angiography has provided unprecedented resolution of retinal vascular flow in a depth resolved manner and demonstrates areas of decreased or absent flow in the deep vascular plexus colocalizing with the cystoid spaces. There has been a large amount of research on fluid management and edema in the brain, much of which may have analogues in the eye. Interstitial flow of fluid as managed by Müller cells may occur in the retina, comparable in some ways to the bulk flow in brain parenchyma, which is managed by astrocytes. Absent blood flow in the deep retinal plexus may restrict fluid management strategies in the retina, to include transport of excess fluid out of the retina into the blood by Müller cells. Application of this theory may help in increasing understanding of the pathophysiology of retinal vascular cystoid macular edema and may lead to new therapeutic approaches.

Perioperative Topical Nonsteroidal Anti-inflammatory Drugs for Macular Edema Prophylaxis Following Cataract Surgery

PURPOSE

To describe the effect of routine use of topical nonsteroidal anti-inflammatory drugs (NSAIDs) on the incidence of postoperative macular edema (PME) after cataract surgery. The role of diabetic retinopathy on the relationship between NSAID use and PME was further analyzed.

DESIGN

Retrospective matched cohort study.

METHODS

Patients undergoing cataract surgery between January 2007 and June 2014 were included in this study. A total of 108 093 Kaiser Permanente Southern California patients underwent cataract surgery and 89 731 met inclusion criteria. Cataract surgery patients who had a perioperative prescription of topical NSAIDs filled in addition to topical steroids were compared to those taking topical steroids only. The main outcome measure was the diagnosis of macular edema within 90 days of cataract surgery.

RESULTS

A prescription for an NSAID was filled by 56.4% of patients. The prevalence of PME was 1.3% among those prescribed and 1.7% among those not prescribed NSAIDs. The number needed to treat was 320 patients to prevent 1 case of PME. A matched cohort analysis was performed to account for confounders. NSAID use was associated with a lower incidence of PME in patients without diabetes [relative risk (RR) 0.68, 95% confidence interval (CI) 0.58-0.72] and diabetics without retinopathy (RR 0.51, 95% CI 0.32-0.82). NSAID use was not associated with a change in the incidence of PME among patients with diabetic retinopathy (RR 1.06, 95% 0.81-1.38).

CONCLUSION

Topical NSAIDs were associated with a modest reduction of PME incidence in patients undergoing cataract surgery; however, this relationship was not seen among those with diabetic retinopathy. The risk for PME is low and the number of patients benefiting from treatment is small.

Implication of VEGF and aquaporin 4 mediating Müller cell swelling to diabetic retinal edema

PURPOSE

Aquaporin 4 (AQP4), a water channel protein, is known to be expressed in retinal Müller cells. The purpose of this study was to determine the effects of VEGF and AQP4 channels on the volumetric changes in Müller cells.

METHODS

Retinas from diabetic rats and a cultured Müller cell line, TR-MUL5, were used in this study. Intravitreal injections of VEGF or PBS were performed on either streptozotocin (STZ)-induced diabetic or normoglycemic rats. Retinal sections were immunostained for anti-glial fibrillary acidic protein (GFAP), anti-AQP4, and anti-VEGF. VEGF protein levels from collected retinas were determined by western blot analysis. Volumetric changes and nitric oxide (NO) levels in cultured Müller cells were determined using flow cytometry (FACS), in the presence or absence of VEGF and TGN-020, a selective AQP4 inhibitor.

RESULTS

In the diabetic rat retina, VEGF immunoreactivity was concentrated in the internal retinal layers, and AQP4 immunoreactivity was higher than controls. The expressions of AQP4 were colocalized with GFAP. Protein levels of VEGF in the hyperglycemic rat retina were significantly higher than controls. FACS analyses showed that exposure to VEGF enlarged Müller cells, while exposure to TGN-020 suppressed the enlargement. Intracellular levels of NO were increased after exposure to VEGF, which was suppressed following the addition of TGN-020.

CONCLUSION

The observed Müller cell swelling is mediated by VEGF and AQP4.

Diabetic retinopathy and OCT angiography: clinical findings and future perspectives

In diabetic retinopathy (DR), macular involvement can present as either macular edema or ischemia. Fluorescein angiography remains the gold standard in the evaluation of retinal vascular perfusion and diagnosis of macular ischemia. However, it is a costly, time-consuming technique, it requires venipuncture, and reports of anaphylaxis and death related to fluorescein injections have been documented, despite their rarity. Optical coherence tomography (OCT) provides a fast and non-invasive method to assess retinal structures at a microscopic level. OCT angiography permits the noninvasive study of retinal and choroid circulation via motion contrast imaging. Split-spectrum amplitude decorrelation angiography combined with OCT angiography has furthered the understanding of retinal and choroidal vascular diseases, allowing the evaluation of retinal microvasculature and identification of subsequent disorders, including DR. Previous studies using OCT angiography have demonstrated that it may demonstrate DR findings such as microaneurysms, arteriolar wall staining, retinal neovascularization, and intraretinal microvascular abnormalities. The purpose of this article is to describe and discuss different concepts regarding OCT angiography, as well as its role in the diagnosis of DR and maculopathy.

Aqueous cytokine and growth factor levels indicate response to ranibizumab for diabetic macular oedema

BACKGROUND/AIMS

To investigate the relations between aqueous humour levels of cytokines/growth factors and treatment response to intravitreal ranibizumab (IVR) for diabetic macular oedema (DME) METHODS: Sixty-eight eyes of 68 patients with treatment-naïve centre-involved DME, central macular thickness (CMT) greater than 400 μm and visual acuity (VA) worse than logMAR 0.3 were recruited. Each patient received monthly IVR injection (0.5 mg/0.05 mL) until CMT was reduced to below 300 μm. Additional IVR was given to maintain CMT below 300 μm during the clinical course of 6 months with monthly follow-up. Aqueous concentrations of cytokines/chemokines and growth factors were measured using samples obtained just before first IVR injection. CMT and VA were monitored monthly for up to 6 months. The number of monthly IVR injections given during the 6-month study period was also recorded.

RESULTS

Twenty-four eyes showed CMT <300 μm soon after the first IVR injection (good responders), while 12 eyes did not reach the goal after six consecutive injections (poor responders). Baseline CMT and VA were not significantly different between the two groups. However, the good responders showed significant increases in baseline aqueous concentrations of vascular endothelial growth factor (VEGF), placenta growth factor, soluble VEGF receptor-1 (sVEGFR1), monocyte chemoattractant protein-1, intercellular adhesion molecule-1, interleukin 6 and inducible protein-10, but not of sVEGFR2, compared with poor responders.

CONCLUSIONS

Response to ranibizumab treatment for DME appears to be associated with aqueous concentrations of VEGFR1 family and certain inflammatory cytokines, but not with clinical parameters.

Prediction of Anti-VEGF Response in Diabetic Macular Edema After 1 Injection

Purpose

With multiple anti-vascular endothelial growth factor and steroid therapies available for diabetic macular edema (DME), there is a need for early determination of the best treatment for a particular patient to prevent irreversible vision loss from chronic DME. In this study, we classify patients as responders or non-responders to anti-vascular endothelial growth factor (VEGF) monotherapy in the treatment of DME after a single anti-VEGF injection.

Methods

The study was designed as a single center, retrospective, interventional case series. We included patients who received 3 consecutive monthly injections with the same anti-VEGF agent. We excluded patients who were treated for DME in the preceding 3 months with any form of anti-VEGF therapy. Visual acuity and central retinal thickness (CRT) data were followed for one year. Receiver operating characteristic (ROC) curve analysis was performed in order to identify cutoff values for identifying responders.

Results

107 eyes were reviewed, with 40 eyes of 34 patients meeting all inclusion criteria. Based on ROC curve analysis, a reduction in CRT by > 15% at 1-month, identified eyes that responded to treatment and had a >25% reduction in CRT at 3-months (sensitivity 0.75, specificity 0.92).

Conclusion

DME eyes that have early response to anti-VEGF treatment by reduction in CRT will have significant response to treatment by 3 months.

Diabetic macular oedema

Diabetic macular oedema, characterised by exudative fluid accumulation in the macula, is the most common form of sight-threatening retinopathy in people with diabetes. It affects one in 15 people with diabetes resulting in more than 20 million cases worldwide. Few epidemiological studies have been done to specifically investigate risk factors for diabetic macular oedema, although poor glycaemic and blood pressure control are associated with the presence and development of the disorder. The pathophysiological processes begin with chronic hyperglycaemia, and interplay between vascular endothelial growth factor (VEGF) and inflammatory mediators. Non-invasive imaging using optical coherence tomography has allowed clinicians to detect mild levels of diabetic macular oedema in order to monitor progress and guide treatment. Although focal or grid laser photocoagulation was the traditional mode of treatment, intraocular pharmacotherapy with anti-VEGF agents is now the standard of care. However, these therapies are expensive and resource intensive. Emerging therapeutic strategies include improving efficacy and duration of VEGF suppression, targeting alternative pathways such as inflammation, the kallikrein-kinin system, the angiopoietin-Tie2 system, and neurodegeneration, and using subthreshold and targeted laser therapy. Ongoing research should lead to improvements in screening, diagnosis, and management of diabetic macular oedema.

Gene therapy for diabetic retinopathy: Are we ready to make the leap from bench to bedside?

Diabetic retinopathy (DR), a chronic and progressive complication of diabetes mellitus, is a sight-threatening disease characterized in the early stages by neuronal and vascular dysfunction in the retina, and later by neovascularization that further damages vision. A major contributor to the pathology is excess production of vascular endothelial growth factor (VEGF), a growth factor that induces formation of new blood vessels and increases permeability of existing vessels. Despite the recent availability of effective treatments for the disease, including laser photocoagulation and therapeutic VEGF antibodies, DR remains a significant cause of vision loss worldwide. Existing anti-VEGF agents, though generally effective, are limited by their short therapeutic half-lives, necessitating frequent intravitreal injections and the risk of attendant adverse events. Management of DR with gene therapies has been proposed for several years, and pre-clinical studies have yielded enticing findings. Gene therapy holds several advantages over conventional treatments for DR, such as a longer duration of therapeutic effect, simpler administration, the ability to intervene at an earlier stage of the disease, and potentially fewer side-effects. In this review, we summarize the current understanding of the pathophysiology of DR and provide an overview of research into DR gene therapies. We also examine current barriers to the clinical application of gene therapy for DR and evaluate future prospects for this approach.

Efficacy of 0.2 μg/day fluocinolone acetonide implant (ILUVIEN) in eyes with diabetic macular edema and prior vitrectomy

Purpose

Limited data are available on the efficacy of the 0.2 μg/day fluocinolone acetonide (FAc) implant in eyes with prior vitrectomy. Here, we present a collection of 26 vitrectomized eyes treated with the 0.2 μg/day FAc implant.

Methods

Retrospective study involving six centers from four European countries analyzing the safety and efficacy data from patients (26 eyes from 25 patients) with DME and a prior vitrectomy that had been treated with one 0.2 μg/day FAc implant.

Results

Prior intravitreal therapies included anti-VEGF (mean, 3.8 injections) and steroids (mean, 1.9 injections). Pars plana vitrectomy (PPV) was performed in these eyes primarily for abnormalities of vitreoretinal interface, followed by proliferative diabetic retinopathy and vitreous hemorrhage. The 0.2 μg/day FAc implant was injected 24.2 months, on average, after PPV and the mean duration of follow-up after injection was 255 days (range, 90 to 759 days). The mean change in BCVA was +11.7 ETDRS letters (range, −19 to +40 letters; P<0.0004) and the mean change in central foveal thickness (CFT) was −233.5 μm (range, −678 to 274 μm; P<0.0001). The mean change in IOP from baseline at the last visit was +1.4 mm Hg (range, −9 to +8 mm Hg; P=0.0090). Eight eyes initiated or continued IOP lowering medications.

Conclusions

These data suggest the 0.2 μg/day FAc implant is effective in vitrectomized patients with an acceptable safety profile. Further studies are still required to confirm the current findings and to assess the effect of the 0.2 μg/day FAc implant over a longer period of follow-up.

Minireview: Fibronectin in retinal disease

Retinal fibrosis, characterized by dysregulation of extracellular matrix (ECM) protein deposition by retinal endothelial cells, pigment epithelial cells, and other resident cell-types, is a unifying feature of several common retinal diseases. Fibronectin is an early constituent of newly deposited ECM and serves as a template for assembly of other ECM proteins, including collagens. Under physiologic conditions, fibronectin is found in all layers of Bruch's membrane. Proliferative vitreoretinopathy (PVR), a complication of retinal surgery, is characterized by ECM accumulation. Among the earliest histologic manifestations of diabetic retinopathy (DR) is capillary basement membrane thickening, which occurs due to perturbations in ECM homeostasis. Neovascularization, the hallmark of late stage DR as well as exudative age-related macular degeneration (AMD), involves ECM assembly as a scaffold for the aberrant new vessel architecture. Rodent models of retinal injury demonstrate a key role for fibronectin in complications characteristic of PVR, including retinal detachment. In mouse models of DR, reducing fibronectin gene expression has been shown to arrest the accumulation of ECM in the capillary basement membrane. Alterations in matrix metalloproteinase activity thought to be important in the pathogenesis of AMD impact the turnover of fibronectin matrix as well as collagens. Growth factors involved in PVR, AMD, and DR, such as PDGF and TGFβ, are known to stimulate fibronectin matrix assembly. A deeper understanding of how pathologic ECM deposition contributes to disease progression may help to identify novel targets for therapeutic intervention.

Novel pharmacotherapies in diabetic retinopathy: Current status and what's in the horizon?

The blood-retinal barrier (BRB) alteration is the hallmark feature of diabetic retinopathy. Vascular endothelial growth factor (VEGF) is a potent vasopermeability factor that has been implicated in the pathogenesis of BRB alteration. Inflammation also plays a crucial role in this process with involvement of several chemokines and cytokines. Multiple anti-VEGF drugs are widely used as in the treatment of diabetic macular edema (DME) as well as proliferative diabetic retinopathy. Several clinical trials have proved the beneficial effects of these drugs in improvement of vision and prevention of vision loss. However, the response to anti-VEGF drugs in DME is not complete in a significant number of patients. The effect seems transient in this latter group, and many patients do not show complete resolution of fluid. Potential novel therapies targeting molecules beyond VEGF are being developed and examined in clinical trials.

Comparison of Cysts in Red and Green Images for Diabetic Macular Edema

PURPOSE

To investigate whether cysts in diabetic macular edema are better visualized in the red channel of color fundus camera images, as compared with the green channel, because color fundus camera screening methods that emphasize short-wavelength light may miss cysts in patients with dark fundi or changes to outer blood retinal barrier.

METHODS

Fundus images for diabetic retinopathy photoscreening were acquired for a study with Aeon Imaging, EyePACS, University of California Berkeley, and Indiana University. There were 2047 underserved, adult diabetic patients, of whom over 90% self-identified as a racial/ethnic identify other than non-Hispanic white. Color fundus images at nominally 45 degrees were acquired with a Canon Cr-DGi non-mydriatic camera (Tokyo, Japan) then graded by an EyePACS certified grader. From the 148 patients graded to have clinically significant macular edema by the presence of hard exudates in the central 1500 μm of the fovea, we evaluated macular cysts in 13 patients with cystoid macular edema. Age ranged from 33 to 68 years. Color fundus images were split into red, green, and blue channels with custom Matlab software (Mathworks, Natick, MA). The diameter of a cyst or confluent cysts was quantified in the red-channel and green-channel images separately.

RESULTS

Cyst identification gave complete agreement between red-channel images and the standard full-color images. This was not the case for green-channel images, which did not expose cysts visible with standard full-color images in five cases, who had dark fundi. Cysts appeared more numerous and covered a larger area in the red channel (733 ± 604 μm) than in the green channel (349 ± 433 μm, P < .006).

CONCLUSIONS

Cysts may be underdetected with the present fundus camera methods, particularly when short-wavelength light is emphasized or in patients with dark fundi. Longer wavelength techniques may improve the detection of cysts and provide more information concerning the early stages of diabetic macular edema or the outer blood retinal barrier.

Diabetic Macular Ischemia Diagnosis: Comparison between Optical Coherence Tomography Angiography and Fluorescein Angiography

Purpose. To compare fluorescein angiography (FA) and optical coherence tomography angiography (OCTA) images of foveal avascular zone (FAZ) in patients with diabetic retinopathy (DR) with and without diabetic macular ischemia (DMI). Methods. The Wilcoxon signed-rank test was used to compare area measurements and p values of <0.05 were considered statistically significant. FA and OCTA images were independently graded by 2 observers that reached agreement regarding quantitative DMI according established protocols. The ischemic area was divided into “large” macular ischemia (superior to 0.32 mm²) and “small” (inferior to 0.32 mm²) groups. Quantitative analyses of the FAZ were performed using custom software. Results. Thirty-four eyes from 34 diabetic patients were enrolled. Subjects with DMI presented a mean area on FA and OCTA of 0.68 ± 0.53 mm² and 0.58 ± 0.35 mm², respectively (p = 0.1374). Patients without DMI presented a mean area on FA and OCTA of 0.19 ± 0.67 mm² and 0.20 ± 0.79 mm², respectively (p = 0.9594). The ICC for the FAZ measurements between the 2 observers on FA and OCTA was 0.96 and 0.92, respectively. Conclusion. OCTA represents a novel technique for the diagnosis of DMI and it may become an alternative to FA for this purpose.

Clinical practice pattern in management of diabetic macular edema in Japan: survey results of Japanese retinal specialists

PURPOSE

To elucidate the current clinical practice patterns of diabetic macular edema (DME) management by retinal specialists in Japan in the era of anti-vascular endothelial growth factor (VEGF) therapy.

METHODS

Forty-six retinal specialists were administered a survey regarding the pathology and clinical practice of DME.

RESULTS

Nearly, half of the specialists (45.2 %) think that the main biochemical factor involved in DME development is the vascular permeability-potentiating action of VEGF-A. Most specialists (70.6 %) use three modalities for detecting DME: optical coherence tomography, fluorescein angiography, and fundus examination. For focal macular edema, focal laser is used as first-line therapy by 70.3 % of specialists, whereas 21.6 % use medical treatment in combination with focal/grid laser. For diffuse macular edema, anti-VEGF therapy is the first choice (72.5 %), irrespective of visual acuity, whereas 17.5 % select off-label sub-Tenon's steroid injections. Vitrectomy is often performed for vitreomacular traction (86.5 %) or when anti-VEGF agent/laser therapy is ineffective (73.2 %). For persistent DME after vitrectomy, anti-VEGF agents (46.3 %) or steroids (intravitreal injections, 14.6 %; sub-Tenon's injections, 36.6 %) are selected. When applying anti-VEGF treatment regimen, most specialists continue loading injections until central retinal thickness stabilized (51.4 %) or both visual acuity and central retinal thickness stabilized (24.3 %). In the maintenance phase, many specialists provide injections with pro re nata (76.3 %), whereas 50.0 % responded that the treat-and-extend regimen is ideal.

CONCLUSIONS

Our survey presents the current views about the DME management and practice patterns of anti-VEGF therapy by one part of the retinal specialists in Japan, and highlights the differences or gaps between evidence and actual clinical practice.

Optical Coherence Tomography Angiography of DME and Its Association with Anti-VEGF Treatment Response

PURPOSE

To investigate the structural integrity of the superficial capillary plexuses (SCPs) and deep capillary plexuses (DCPs) using optical coherence tomography (OCT) angiography (OCTA) in patients with diabetic macular edema (DME) and its association with the response to anti-vascular endothelial growth factor (VEGF) treatment.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

We included 51 DME eyes with a poor response to anti-VEGF agents and 32 age-matched DME eyes with a good response to anti-VEGF treatment, along with 20 fellow eyes without DME from the cases and controls.

METHODS

The medical records, including OCTA and spectral-domain OCT (SD OCT), were reviewed and compared between the groups. En face OCTA images of the SCP and DCP were obtained for each eye. An anti-VEGF responder was defined by a reduction of more than 50 μm in central retinal thickness after 3 consecutive anti-VEGF treatments. A poor responder was defined by a reduction of less than 50 μm or an increase in central retinal thickness after 3 monthly injections.

MAIN OUTCOME MEASURES

We measured the vascular density and foveal avascular zone (FAZ) area and counted the number of microaneurysms in each layer. The SD OCT images were compared with OCTA findings.

RESULTS

Compared with non-DME eyes, DME eyes had a lower vascular density (P < 0.001) and larger FAZ area (P < 0.001) in the DCP and more microaneurysms (P < 0.001) in both layers. Although there was no significant difference in the SCP between anti-VEGF responders and poor responders, poor responders tended to show greater damage and more microaneurysms in the DCP (P < 0.001) and a larger FAZ area (P < 0.001). The topographic location of the disrupted synaptic portion of the outer plexiform layer (OPL) in SD OCT exactly corresponded to the nonflow area of the DCP in OCTA.

CONCLUSIONS

Compared with DME eyes that responded to anti-VEGF treatment, poor responders show significant damage to the integrity of the DCP, but not the SCP. The degree of OPL disruption in SD OCT corresponds well with the extent of DCP loss in DME eyes. The extent of DCP loss and the corresponding OPL disruption could be useful predictors of responsiveness to anti-VEGF treatment.

The relationship between anti-vascular endothelial growth factor and fibrosis in proliferative retinopathy: clinical and laboratory evidence

PURPOSE

To investigate the progression of epiretinal membranes after intravitreal bevacizumab (IVB) injection therapy in patients with proliferative membranes and evaluate the changes in fibrosis-related cytokines in retinal pigment epithelial cells and glial cells after treatment with bevacizumab.

METHODS

Retrospective study of the proliferative membranes in patients with and without IVB therapy. In vitro, the human adult retinal pigment epithelial (ARPE-19) cells and BV2 microglial cell lines were incubated in different bevacizumab concentrations under hypoxic conditions. Cell culture supernatants and cell lysates were harvested after incubation for 24, 48 or 72 hours for ELISA and western blot.

RESULTS

Bevacizumab accelerated fibrosis in patients with proliferative membranes. Immunofluorescence analysis revealed more intense transforming growth factor β2 (TGFβ2) and connective tissue growth factor (CTGF) staining in IVB-treated proliferative diabetic retinopathy (PDR) membranes compared with membranes of patients not receiving IVB therapy. This result was consistent with real-time PCR results. Bevacizumab incubation significantly upregulated TGFβ2 and CTGF in ARPE-19 cells and BV2 microglial cells, but ciliary neurotrophic factor (CNTF) expression was upregulated only in BV2 microglial cells.

CONCLUSIONS

Anti-vascular endothelial growth factor treatment likely accelerates fibrosis in PDR patients via upregulation of TGFβ2, CTGF and CNTF, suggesting the importance of adjunctive therapy for retinal fibrosis.

Neurovascular cross talk in diabetic retinopathy: Pathophysiological roles and therapeutic implications

Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population in developed countries, and its prevalence will increase as the global incidence of diabetes grows exponentially. DR begins with an early nonproliferative stage in which retinal blood vessels and neurons degenerate as a consequence of chronic hyperglycemia, resulting in vasoregression and persistent retinal ischemia, metabolic disequilibrium, and inflammation. This is conducive to overcompensatory pathological neovascularization associated with advanced proliferative DR. Although DR is considered a microvascular complication, the retinal microvasculature is intimately associated with and governed by neurons and glia; neurodegeneration, neuroinflammation, and dysregulation of neurovascular cross talk are responsible in part for vascular abnormalities in both early nonproliferative DR and advanced proliferative DR. Neuronal activity directly regulates microvascular dilation and blood flow in the process of neurovascular coupling. Retinal neurons also secrete guidance cues in response to injury, ischemia, or metabolic stress that may either promote or suppress vascular outgrowth, either alleviating or exacerbating DR, contingent on the stage of disease and retinal microenvironment. Neurodegeneration, impaired neurovascular coupling, and dysregulation of neuronal guidance cues are key events in the pathogenesis of DR, and correcting these events may prevent or delay development of advanced DR. The review discusses the mechanisms of neurovascular cross talk and its dysregulation in DR, and their potential therapeutic implications.

Matrix Metalloproteinase-1 and Matrix Metalloproteinase-9 in the Aqueous Humor of Diabetic Macular Edema Patients

Purpose

To assess the concentrations of matrix metalloproteinase (MMP)-1 and MMP-9 in the aqueous humor of diabetic macular edema (DME) patients.

Method

The concentrations of MMP-1 and MMP-9 in the aqueous humors of 15 cataract patients and 25 DME patients were compared. DME patients were analyzed according to the diabetic retinopathy (DR) stage, diabetes mellitus (DM) duration, pan-retinal photocoagulation (PRP) treatment, recurrence within 3 months, HbA1C (glycated hemoglobin) level, and axial length.

Results

The concentrations of MMP-1 and MMP-9 of the DME groups were higher than those of the control group (p = 0.005 and p = 0.002, respectively). There was a significant difference in MMP-1 concentration between the mild non-proliferative diabetic retinopathy (NPDR) group and the proliferative diabetic retinopathy (PDR) group (p = 0.012). MMP-1 concentrations were elevated in PRP-treated patients (p = 0.005). There was a significant difference in MMP-9 concentrations between the mild NPDR group and the PDR group (p < 0.001), and between the moderate and severe NPDR group and the PDR group (p < 0.001). The MMP-9 concentrations in PRP treated patients, DM patients with diabetes ≥ 10 years and recurrent DME within 3months were elevated (p = 0.023, p = 0.011, and p = 0.027, respectively). In correlation analyses, the MMP-1 level showed a significant correlation with age (r = -0.48, p = 0.01,), and the MMP-9 level showed significant correlations with axial length (r = -0.59, p < 0.01) and DM duration (r = 049, p = 0.01).

Conclusions

Concentrations of MMP-1 and MMP-9 were higher in the DME groups than in the control group. MMP-9 concentrations also differed depending on DR staging, DM duration, PRP treatment, and degree of axial myopia. MMP-9 may be more important than MMP-1 in the induction of DM complications in eyes.

LRP-1 Pathway Targeted Inhibition of Vascular Abnormalities in the Retina of Diabetic Mice

PURPOSE

The cell surface LDL (low-density lipoprotein) receptor-related protein-1 (LRP-1) is important for lipid transport and several cell signaling processes. Human apolipoprotein E (apoE) is a ligand of LRP-1. We previously reported that a short peptide (apoEdp) mimicking the LRP-1 binding region of apoE prevents hyperglycemia-induced retinal endothelial cell dysfunction in vitro. The in-vivo outcome of apoE-based peptidomimetic inhibition of LRP-1 in the treatment of diabetic retinopathy is unknown.

METHODS

Six months after streptozotocin induction of diabetes, male C57Bl/6 mice were intravitreally inoculated with apoEdp in a controlled release formulation. On the 15th day post-apoEdp treatment, mouse retinas were harvested to examine (1) blood-retinal-barrier (BRB) permeability by Evans blue dye, inflammatory leukostasis by concanavalin staining of leukocytes and LRP-1 pathway-related protein expression by Western blot analysis and gelatin zymography.

RESULTS

Intravitreal apoEdp treatment of diabetic mice significantly reduced Evans blue extravasation and the number of adherent leukocytes in the diabetic mouse retinas. ApoEdp treatment inhibited the expression of extracellular matrix (ECM) degrading proteases heparanase and MMP-2, and restores the BRB tight junction proteins occludin and ZO-1. ApoEdp treatment also inhibited Wnt/β-catenin-related expression of pro-inflammatory molecules ICAM-1, HIF-1α, and VEGF through negative regulation by LRP-1.

CONCLUSION

Intravitreal apoEdp treatment of diabetic mice resulted a significant decrease in retinal vascular abnormalities through downregulation of LRP-1-related ECM protein degradation and Wnt/β-catenin-related pro-angiogenic molecules.

The Efficacy and Safety of Current Treatments in Diabetic Macular Edema: A Systematic Review and Network Meta-Analysis

Purpose

To compare the efficacy and safety of current treatments in diabetic macular edema (DME).

Methods

PubMed, Embase and CENTRAL were systematically reviewed for randomized controlled trials of current treatments in DME through August 2015. Data on the mean change of best-corrected visual acuity (BCVA) and central macular thickness (CMT) were extracted, and adverse events (AEs) were collected.

Results

A total of 21 trials were included in our network meta-analysis. Intravitreal ranibizumab improved BCVA most significantly (OR: +7.01 95%CI (2.56 to 11.39)) in 6 months and intravitreal aflibercept (+8.19 (5.07 to 11.96)) in 12 months. Intravitreal triamcinolone combined with LASER decreased CMT most significantly (-111.34 (-254.61 to 37.93)) in 6 months and intravitreal aflibercept (-110.83 (-190.25 to -35.27)) in 12 months. Compared with the relatively high rate of ocular AEs in the groups with administration of steroids, systematic AEs occurred more frequently in the groups with vascular endothelial growth factor inhibitors involved.

Conclusions

Our analysis confirms that intravitreal aflibercept is most favorable with both BCVA improvement and CMT decrease than other current therapies in the management of DME within 12 months. Vascular endothelial growth factor inhibitors for DME should be used with caution due to systematic AEs. Combined intravitreal triamcinolone with LASER has a stronger efficacy in decreasing CMT than the other interventions in the early stage after injection. More high-quality randomized controlled trials will be necessary.

Efficacy and safety of sustained-delivery fluocinolone acetonide intravitreal implant in patients with chronic diabetic macular edema insufficiently responsive to available therapies: a real-life study

Purpose

To evaluate the efficacy and safety of sustained-delivery fluocinolone acetonide (FAc) intravitreal implant for diabetic macular edema (DME).

Patients and methods

Prospective study in patients with DME insufficiently responsive to laser and anti-vascular endothelial growth factor (anti-VEGF). Patients with history of rise of intraocular pressure after intravitreal corticosteroids were excluded.

Results

The macular edema rapidly decreased both in group 1 (prior laser only; n=7 eyes) and group 2 (prior laser and ≥3 monthly anti-VEGF therapy; n=10 eyes) and central subfield thickness was reduced by −299 μm (P=0.008) and −251 μm (P=0.016) at 12 months, respectively. Mean area under the curve from baseline to last value for pseudophakic eyes was +4.2 letters in group 1 and +9.5 letters in group 2. Overall, the FAc implant was well tolerated.

Conclusion

This prospective study confirms the efficacy of the FAc implant in DME patients insufficiently responsive to laser and anti-VEGF. Moreover, with a careful patient selection, our safety results would support an earlier use of FAc in the DME treatment pathway.

Prospective randomised clinical trial to evaluate the safety and efficacy of nepafenac 0.1% treatment for the prevention of macular oedema associated with cataract surgery in patients with diabetic retinopathy

BACKGROUND/AIMS

This study evaluated nepafenac ophthalmic suspension 0.1% for prevention of macular oedema (MO) when used 90 days following cataract surgery in patients with diabetic retinopathy (DR).

METHODS

Randomised, double-masked, vehicle-controlled, parallel group study conducted at 32 centres across the world. Participants were patients with diabetes with non-proliferative diabetic retinopathy scheduled for cataract surgery with (posterior chamber) intraocular lens implantation. Patients were randomised to nepafenac ophthalmic suspension 0.1% or vehicle three times daily, beginning on the day before surgery and continuing through the last study visit (day 90 or early exit). All patients were instilled one drop of tobramycin 0.3% and dexamethasone 0.1% four times daily for 2 weeks after surgery. Primary efficacy end point was the percentage of patients who developed MO (defined as ≥30% increase in central subfield macular thickness from baseline) within 90 days following surgery. The secondary end point was mean change in best-corrected visual acuity (BCVA) from baseline to day 90.

RESULTS

A total of 175 patients were randomised, with 87 and 88 patients in the nepafenac and vehicle groups, respectively. A significantly greater percentage of eyes in the vehicle group (17.5%; 95% CI 9.9% to 27.6%) developed MO within 90 days following surgery compared with the nepafenac group (5.0%; 95% CI 1.4% to 12.3%, p=0.01). Mean change in BCVA from baseline to day 90 following surgery was greater in the nepafenac group (17.7±14.6 letters) relative to the vehicle group (14.3±13.9 letters), though the difference was not statistically significant (p=0.14). No new safety issues or trends were identified.

CONCLUSIONS

A 90-day nepafenac treatment regimen prevented MO after cataract surgery in patients with DR and demonstrated no safety issues within this study group.

TRIAL REGISTRATION NUMBER

NTC00782717 and NCT00939276.

Deletion of miR-150 Exacerbates Retinal Vascular Overgrowth in High-Fat-Diet Induced Diabetic Mice

Diabetic retinopathy (DR) is the leading cause of blindness among American adults above 40 years old. The vascular complication in DR is a major cause of visual impairment, making finding therapeutic targets to block pathological angiogenesis a primary goal for developing DR treatments. MicroRNAs (miRs) have been proposed as diagnostic biomarkers and potential therapeutic targets for various ocular diseases including DR. In diabetic animals, the expression levels of several miRs, including miR-150, are altered. The expression of miR-150 is significantly suppressed in pathological neovascularization in mice with hyperoxia-induced retinopathy. The purpose of this study was to investigate the functional role of miR-150 in the development of retinal microvasculature complications in high-fat-diet (HFD) induced type 2 diabetic mice. Wild type (WT) and miR-150 null mutant (miR-150-/-) male mice were given a HFD (59% fat calories) or normal chow diet. Chronic HFD caused a decrease of serum miR-150 in WT mice. Mice on HFD for 7 months (both WT and miR-150-/-) had significant decreases in retinal light responses measured by electroretinograms (ERGs). The retinal neovascularization in miR-150-/--HFD mice was significantly higher compared to their age matched WT-HFD mice, which indicates that miR-150 null mutation exacerbates chronic HFD-induced neovascularization in the retina. Overexpression of miR-150 in cultured endothelial cells caused a significant reduction of vascular endothelial growth factor receptor 2 (VEGFR2) protein levels. Hence, deletion of miR-150 significantly increased the retinal pathological angiogenesis in HFD induced type 2 diabetic mice, which was in part through VEGFR2.

Elevated Intraocular Pressure After Intravitreal Steroid Injection in Diabetic Macular Edema: Monitoring and Management

INTRODUCTION

With the increasing use of intravitreal administration of corticosteroids in macular edema, steroid-induced intraocular pressure (IOP) rise is becoming an emergent issue. However, for patients in whom intravitreal steroids are indicated, there are no specific recommendations for IOP monitoring and management after intravitreal administration of corticosteroids.

METHOD

An expert panel of European ophthalmologists reviewed evidence on corticosteroid-induced IOP elevation. The objective of the panel was to propose an algorithm based on available literature and their own experience for the monitoring and management of corticosteroid-induced IOP elevation, with a focus on diabetic patients.

RESULTS

Data from trials including diabetic patients with a rise of IOP after intravitreal steroid administration indicate that IOP-lowering medical treatment is sufficient for a large majority of patients; only a small percentage underwent laser trabeculoplasty or filtering filtration surgery. A 2-step algorithm is proposed that is based on the basal value of IOP and evidence for glaucoma. The first step is a risk stratification before treatment. Patients normotensive at baseline (IOP ≤ 21 mmHg), do not require additional baseline diagnostic tests. However, patients with baseline ocular hypertension (OHT) (IOP > 21 mmHg) should undergo baseline imaging and visual field testing. The second step describes monitoring and treatment after steroid administration. During follow-up, patients developing OHT should have baseline and periodical imaging and visual field testing; IOP-lowering treatment is proposed only if IOP is >25 mmHg or if diagnostic tests suggest developing glaucoma.

CONCLUSION

The management and follow-up of OHT following intravitreal corticosteroid injection is similar to that of primary OHT. If OHT develops, IOP is controlled in a large proportion of patients with standard IOP treatments. The present algorithm was developed to assist ophthalmologists with guiding principles in the management of corticosteroid-induced IOP elevation.

FUNDING

Alimera Sciences Limited.

Multimodal retinal imaging of diabetic macular edema: toward new paradigms of pathophysiology

The pathophysiology of diabetic macular edema (DME) is multifactorial and partly still unknown. An increasing body of evidence suggests that neurodegeneration and retinal glial cells activation occur even before the earliest clinical manifestation of diabetic retinal vasculopathy. Nowadays, new non-invasive techniques are available to assess and characterize DME, not only in a quantitative perspective, but also making it possible to understand and quantify the pathogenic processes sustaining fluid accumulation. Optical coherence tomography (OCT) allows documenting not only parameters such as macular volume, central and sectorial retinal thickness, fluid localization, and integrity of retinal layers, but also new still poorly investigated reflectivity aspects. Hyperreflective intraretinal spots (HRS) have been detected on OCT scans through the retinal layers, with a presumptive migration pattern towards the external layers during the occurrence of diabetic retinopathy and DME. These HRS have been hypothesised to represent an in-vivo marker of microglial activation. Autofluorescence of the fundus (FAF) also offers a non-invasive imaging technique of DME. The area of increased FAF correlates with the presence of intraretinal fluid and probably retinal glial activation. Microperimetry allows the measurement of retinal sensitivity by testing specific selected retinal areas. Some studies have shown that increased macular FAF in DME correlates better with visual function assessed with microperimetry than with visual acuity, showing that new imaging and functional techniques may help to elucidate DME pathogenesis and to target therapeutical strategies.

Intravitreal injection of methotrexate in persistent diabetic macular edema: a 6-month follow-up study

PURPOSE

To evaluate the efficacy of intravitreal injection of methotrexate (MTX) in patients with persistent diabetic macular edema (DME) nonresponsive to intravitreal bevacizumab.

METHODS

In this prospective, interventional study, intravitreal injection of 400 μg MTX was performed in eyes with persistent center-involving DME unresponsive to at least three consecutive bevacizumab injections or two consecutive bevacizumab injections plus macular photocoagulation. Best-corrected visual acuity (BCVA), central subfield thickness (CST), and maximum retinal thickness (MRT) were recorded before and 1, 3, and 6 months after injections.

RESULTS

Eighteen eyes of 16 patients with a mean age of 61.1 ± 6.7 years were included. Mean number of intravitreal bevacizumab injections was 3.9 ± 1.8 (range 2-8). The mean change in BCVA was -0.09 ± 0.19, -0.1 ± 0.19, and -0.1 ± 0.19 LogMAR at 1, 3, and 6 months after intravitreal MTX injections, respectively (all P = 0.04). Three eyes (16.6 %) had improvement of at least two lines of BCVA and no eye lost visual acuity. Mean change in CST was -23.7 ± 66.7, -28.7 ± 82.2 and 26.5 ± 83.4 μm at 1, 3, and 6 months after MTX injections, respectively (all P = 0.1). A decrease in CST was found in 13 eyes (72.2 %) at 1 and 3 months, and seven eyes (38.8 %) at 6 months of follow-up. Other eyes showed an increase in CST measurements. Mean change in MRT was -35.1 ± 76.4, -40.6 ± 86.3, and 29.8 ± 68.6 μm at 1, 3, and 6 months after MTX injections, respectively (P = 0.06, P = 0.06, and P = 0.08, respectively). No complication attributable to intravitreal MTX occurred.

CONCLUSION

In this study, intravitreal injection of MTX resulted in anatomical improvement in a significant proportion of eyes with persistent DME. Significant visual improvement was found in 16.6 % of eyes.

Visual and Anatomic Outcomes in Patients with Diabetic Macular Edema with Limited Initial Anatomic Response to Ranibizumab in RIDE and RISE

PURPOSE

To explore the visual acuity and anatomic outcomes over 24 months of patients with diabetic macular edema (DME) who showed a delayed anatomic response after 3 ranibizumab injections in the RIDE and RISE trials.

DESIGN

Analysis of data from RIDE and RISE, 2 phase III, parallel, randomized, multicenter, double-masked trials (ClinicalTrials.gov identifiers, NCT00473382 and NCT00473330).

PARTICIPANTS

Patients with DME (n = 681) who received monthly intravitreal ranibizumab 0.3-mg injections, ranibizumab 0.5-mg injections, or sham injections.

METHODS

Patients were separated into 3 groups: delayed responders (ranibizumab-treated patients with ≤10% central foveal thickness [CFT] reduction after 3 injections), immediate responders (ranibizumab-treated patients with >10% CFT reduction after 3 injections), and sham recipients. Central foveal thickness was measured by time-domain optical coherence tomography, best-corrected visual acuity (BCVA) was measured by Early Treatment Diabetic Retinopathy Study (ETDRS) letter scores, and diabetic retinopathy (DR) was measured by the standardized ETDRS severity scale (using fundus photographs).

MAIN OUTCOME MEASURES

Month-24 CFT, BCVA, and DR severity levels.

RESULTS

In RIDE and RISE, 9% to 10% of ranibizumab-treated eyes were delayed responders. At month 24, delayed responders had less CFT reduction (median, -102 μm) from baseline compared with immediate responders (median, -274 μm; P < 0.0001). Delayed responders gained a median of 10 letters at 24 months, similar to immediate responders (14 letters; P = 0.15). At month 24, DR improvement among the delayed responders (31% and 22% of patients with ≥2- or ≥3-step DR improvement, respectively) was comparable with that among immediate responders (42% and 17%, respectively; P = 0.21 and P = 0.48, respectively).

CONCLUSIONS

With continued treatment, at month 24, patients with DME with delayed anatomic response (≤10% CFT reduction) after 3 ranibizumab injections had visual acuity gains and DR improvement similar to those of patients with DME who had immediate anatomic response.

Novel strategies for the treatment of diabetic macular edema

Macular edema such as diabetic macular edema (DME) and diabetic retinopathy are devastating back-of-the-eye retinal diseases leading to loss of vision. This area is receiving considerable medical attention. Posterior ocular diseases are challenging to treat due to complex ocular physiology and barrier properties. Major ocular barriers are static (corneal epithelium, corneal stroma, and blood-aqueous barrier) and dynamic barriers (blood-retinal barrier, conjunctival blood flow, lymph flow, and tear drainage). Moreover, metabolic barriers impede posterior ocular drug delivery and treatment. To overcome such barriers and treat back-of-the-eye diseases, several strategies have been recently developed which include vitreal drainage, laser photocoagulation and treatment with biologics and/or small molecule drugs. In this article, we have provided an overview of several emerging novel strategies including nanotechnology based drug delivery approach for posterior ocular drug delivery and treatment with an emphasis on DME.

A Drug Delivery System for Administration of Anti-TNF-α Antibody

PURPOSE

To describe the fabrication, evaluation, and preliminary in vivo safety of a new drug delivery system (DDS) for topical anti-TNF-α antibody administration.

METHODS

A DDS was fabricated using inverse template fabrication of a hydrophobic three-dimensional porous scaffold (100-300 μm in diameter porosity) loaded with 10% polyvinyl alcohol hydrogel carrying 5 mg/ml (weight/volume) of anti-TNF-α antibody. Drug-loaded DDS was sterilized with 25 kGy of gamma irradiation. Long-term in vitro antibody affinity and release was evaluated at room temperature or 37°C using enzyme-linked immunosorbent assay (ELISA) and protein fluorescence. In vivo clinical and histolopathological assessment was performed by subcutaneous implantation in BALB/c mice for 3 months.

RESULTS

Gamma irradiation, repeated dry/wet cycles, and storage at room temperature for 1 year or 37°C for 1 month had no deleterious effects on antibody affinity. Anti-TNF-α release was high during the first minutes of aqueous exposure, followed by stabilization and gradual, low-dose, antibody release over the next 30 days. Histopathologic evaluation of explanted DDS showed a fibrous pseudocapsule and a myxoid acute/chronic inflammation without granuloma formation surrounding the implants.

CONCLUSIONS

Sustained local delivery of anti-TNF-α antibody is feasible using the described DDS, which provides stability of the enclosed antibody for up to 1 year of storage. Preliminary results show good in vivo tolerance following subcutaneous placement for 3 months. The proposed fabrication and sterilization process opens new possibilities for the delivery of biologic agents to the anterior surface of the eye.

TRANSLATIONAL RELEVANCE

The described DDS will facilitate the treatment of ocular surface diseases amenable to biologic therapy.

Basement membrane stiffening promotes retinal endothelial activation associated with diabetes

Endothelial activation is a hallmark of the high-glucose (HG)-induced retinal inflammation associated with diabetic retinopathy (DR). However, precisely how HG induces retinal endothelial activation is not fully understood. We hypothesized that HG-induced up-regulation of lysyl oxidase (LOX), a collagen-cross-linking enzyme, in retinal capillary endothelial cells (ECs) enhances subendothelial basement membrane (BM) stiffness, which, in turn, promotes retinal EC activation. Diabetic C57BL/6 mice exhibiting a 70 and 50% increase in retinal intercellular adhesion molecule (ICAM)-1 expression and leukocyte accumulation, respectively, demonstrated a 2-fold increase in the levels of BM collagen IV and LOX, key determinants of capillary BM stiffness. Using atomic force microscopy, we confirmed that HG significantly enhances LOX-dependent subendothelial matrix stiffness in vitro, which correlated with an ∼2.5-fold increase in endothelial ICAM-1 expression, a 4-fold greater monocyte-EC adhesion, and an ∼2-fold alteration in endothelial NO (decrease) and NF-κB activation (increase). Inhibition of LOX-dependent subendothelial matrix stiffening alone suppressed HG-induced retinal EC activation. Finally, using synthetic matrices of tunable stiffness, we demonstrated that subendothelial matrix stiffening is necessary and sufficient to promote EC activation. These findings implicate BM stiffening as a critical determinant of HG-induced retinal EC activation and provide a rationale for examining BM stiffness and underlying mechanotransduction pathways as therapeutic targets for diabetic retinopathy.

Diabetic Retinopathy: Animal Models, Therapies, and Perspectives

Diabetic retinopathy (DR) is one of the major complications of diabetes. Although great efforts have been made to uncover the mechanisms underlying the pathology of DR, the exact causes of DR remain largely unknown. Because of multifactor involvement in DR etiology, currently no effective therapeutic treatments for DR are available. In this paper, we review the pathology of DR, commonly used animal models, and novel therapeutic approaches. Perspectives and future directions for DR treatment are discussed.