Diabetic Macular Edema

Aquaporin 11 alleviates retinal Müller intracellular edema through water efflux in diabetic retinopathy

Retinal Müller glial dysfunction and intracellular edema are important mechanisms leading to diabetic macular edema (DME). Aquaporin 11 (AQP11) is primarily expressed in Müller glia with unclear functions. This study aims to explore the role of AQP11 in the pathogenesis of intracellular edema of Müller glia in diabetic retinopathy (DR). Here, we found that AQP11 expression, primarily located at the endfeet of Müller glia, was down-regulated with diabetes progression, accompanied by intracellular edema, which was alleviated by intravitreal injection of lentivirus-mediated AQP11 overexpression. Similarly, intracellular edema of hypoxia-treated rat Müller cell line (rMC-1) was aggravated by AQP11 inhibition, while attenuated by AQP11 overexpression, accompanied by enhanced function in glutamate metabolism and reduced cell death. The down-regulation of AQP11 was also verified in the Müller glia from the epiretinal membranes (ERMs) of proliferative DR (PDR) patients. Mechanistically, down-regulation of AQP11 in DR was mediated by the HIF-1α-dependent and independent miRNA-AQP11 axis. Overall, we deciphered the AQP11 down-regulation, mediated by miRNA-AQP11 axis, resulted in Müller drainage dysfunction and subsequent intracellular edema in DR, which was partially reversed by AQP11 overexpression. Our findings propose a novel mechanism for the pathogenesis of DME, thus targeting AQP11 regulation provides a new therapeutic strategy for DME.

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

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

Involvement of Cytokines in the Pathogenesis of Diabetic Macular Edema

Diabetic macular edema (DME) is a critical complication of diabetic retinopathy, a condition that arises from the breakdown of the blood–retinal barrier and the consequent increase in vascular permeability. Over the years, attempts have been made to treat DME by various approaches, including laser photocoagulation, steroid triamcinolone acetonide, and vitrectomy. However, treatment was unsatisfactory until research identified vascular endothelial growth factor (VEGF) as a factor in the pathogenesis of DME. Intraocular anti-VEGF agents show good efficacy in DME. Nevertheless, in some patients the condition recurs or becomes resistant to treatment, suggesting that other factors may be involved. Because inflammation and retinal hypoxia are seen in DME, research has examined the potential role of cytokines and other inflammatory mediators. In this review, we provide an overview of this research and describe feedback mechanisms that may represent a target for novel treatments.

Human vitreous in proliferative diabetic retinopathy: Characterization and translational implications

Diabetic retinopathy (DR) is one of the leading causes of visual impairment in the working-age population. DR is a progressive eye disease caused by long-term accumulation of hyperglycaemia-mediated pathological alterations in the retina of diabetic patients. DR begins with asymptomatic retinal abnormalities and may progress to advanced-stage proliferative diabetic retinopathy (PDR), characterized by neovascularization or preretinal/vitreous haemorrhages. The vitreous, a transparent gel that fills the posterior cavity of the eye, plays a vital role in maintaining ocular function. Structural and molecular alterations of the vitreous, observed during DR progression, are consequences of metabolic and functional modifications of the retinal tissue. Thus, vitreal alterations reflect the pathological events occurring at the vitreoretinal interface. These events are caused by hypoxic, oxidative, inflammatory, neurodegenerative, and leukostatic conditions that occur during diabetes. Conversely, PDR vitreous can exert pathological effects on the diabetic retina, resulting in activation of a vicious cycle that contributes to disease progression. In this review, we recapitulate the major pathological features of DR/PDR, and focus on the structural and molecular changes that characterize the vitreal structure and composition during DR and progression to PDR. In PDR, vitreous represents a reservoir of pathological signalling molecules. Therefore, in this review we discuss how studying the biological activity of the vitreous in different in vitro, ex vivo, and in vivo experimental models can provide insights into the pathogenesis of PDR. In addition, the vitreous from PDR patients can represent a novel tool to obtain preclinical experimental evidences for the development and characterization of new therapeutic drug candidates for PDR therapy.

Diabetic Macular Edema Pathophysiology: Vasogenic versus Inflammatory

Diabetic macular edema (DME) can cause blindness in diabetic patients suffering from diabetic retinopathy (DR). DM parameters controls (glycemia, arterial tension, and lipids) are the gold standard for preventing DR and DME. Although the vascular endothelial growth factor (VEGF) is known to play a role in the development of DME, the pathological processes leading to the onset of this disease are highly complex and the exact sequence in which they occur is still not completely understood. Angiogenesis and inflammation have been shown to be involved in the pathogenesis of this disease. However, it still remains to be clarified whether angiogenesis following VEGF overexpression is a cause or a consequence of inflammation. This paper provides a review of the data currently available, focusing on VEGF, angiogenesis, and inflammation. Our analysis suggests that angiogenesis and inflammation act interdependently during the development of DME. Knowledge of DME etiology seems to be important in treatments with anti-VEGF or anti-inflammatory drugs. Current diagnostic techniques do not permit us to differentiate between both etiologies. In the future, diagnosing the physiopathology of each patient with DME will help us to select the most effective drug.

Anti-vascular endothelial growth factor for diabetic macular oedema

BACKGROUND

Diabetic macular oedema (DMO) is a common complication of diabetic retinopathy. Although grid or focal laser photocoagulation has been shown to reduce the risk of visual loss in DMO, or clinically significant macular oedema (CSMO), vision is rarely improved. Antiangiogenic therapy with anti-vascular endothelial growth factor (anti-VEGF) modalities is used to try to improve vision in people with DMO.

OBJECTIVES

To investigate the effects in preserving and improving vision and acceptability, including the safety, compliance with therapy and quality of life, of antiangiogenic therapy with anti-VEGF modalities for the treatment of DMO.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 3), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to April 2014), EMBASE (January 1980 to April 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to April 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 28 April 2014.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing any antiangiogenic drugs with an anti-VEGF mechanism of action versus another treatment, sham treatment or no treatment in people with DMO.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration. The risk ratios (RR) for visual loss and visual gain of three or more lines of logMAR visual acuity were estimated at one year of follow-up (plus or minus six months) after treatment initiation.

MAIN RESULTS

Eighteen studies provided data on four comparisons of interest in this review. Participants in the trials had central DMO and moderate vision loss.Compared with grid laser photocoagulation, people treated with antiangiogenic therapy were more likely to gain 3 or more lines of vision at one year (RR 3.6, 95% confidence interval (CI) 2.7 to 4.8, 10 studies, 1333 cases, high quality evidence) and less likely to lose 3 or more lines of vision (RR 0.11, 95% CI 0.05 to 0.24, 7 studies, 1086 cases, high quality evidence). In meta-analyses, no significant subgroup difference was demonstrated between bevacizumab, ranibizumab and aflibercept for the two primary outcomes, but there was little power to detect a difference. The quality of the evidence was judged to be high, because the effect was large, precisely measured and did not vary across studies, although some studies were at high or unclear risk of bias for one or more domains. Regarding absolute benefit, we estimated that 8 out of 100 participants with DMO may gain 3 or more lines of visual acuity using photocoagulation whereas 28 would do so with antiangiogenic therapy, meaning that 100 participants need to be treated with antiangiogenic therapy to allow 20 more people (95% CI 13 to 29) to markedly improve their vision after one year. People treated with anti-VEGF on average had 1.6 lines better vision (95% CI 1.4 to 1.8) after one year compared to laser photocoagulation (9 studies, 1292 cases, high quality evidence). To achieve this result, seven to nine injections were delivered in the first year and three or four in the second, in larger studies adopting either as needed regimens with monthly monitoring or fixed regimens.In other analyses antiangiogenic therapy was more effective than sham (3 studies on 497 analysed participants, high quality evidence) and ranibizumab associated with laser was more effective than laser alone (4 studies on 919 participants, high quality evidence).Ocular severe adverse events, such as endophthalmitis, were rare in the included studies. Meta-analyses conducted for all antiangiogenic drugs compared with either sham or photocoagulation did not show a significant difference regarding serious systemic adverse events (15 studies, 441 events in 2985 participants, RR 0.98, 95% CI 0.83 to 1.17), arterial thromboembolic events (14 studies, 129 events in 3034 participants, RR 0.89, 95% CI 0.63 to 1.25) and overall mortality (63 events in 3562 participants, RR 0.88, 95% CI 0.52 to 1.47). We judged the quality of the evidence on adverse effects as moderate due to partial reporting of safety data and the exclusion of participants with previous cardiovascular events in some studies.

AUTHORS' CONCLUSIONS

There is high quality evidence that antiangiogenic drugs provide a benefit compared to current therapeutic options for DMO, that is grid laser photocoagulation, in clinical trial populations at one or two years. Future research should investigate differences between drugs, effectiveness under real-world monitoring and treatment conditions, and safety in high-risk populations, particularly regarding cardiovascular risk.

Nanomedicines for back of the eye drug delivery, gene delivery, and imaging

Treatment and management of diseases of the posterior segment of the eye such as diabetic retinopathy, retinoblastoma, retinitis pigmentosa, and choroidal neovascularization is a challenging task due to the anatomy and physiology of ocular barriers. For instance, traditional routes of drug delivery for therapeutic treatment are hindered by poor intraocular penetration and/or rapid ocular elimination. One possible approach to improve ocular therapy is to employ nanotechnology. Nanomedicines, products of nanotechnology, having at least one dimension in the nanoscale include nanoparticles, micelles, nanotubes, and dendrimers, with and without targeting ligands. Nanomedicines are making a significant impact in the fields of ocular drug delivery, gene delivery, and imaging, the focus of this review. Key applications of nanotechnology discussed in this review include a) bioadhesive nanomedicines; b) functionalized nanomedicines that enhance target recognition and/or cell entry; c) nanomedicines capable of controlled release of the payload; d) nanomedicines capable of enhancing gene transfection and duration of transfection; f) nanomedicines responsive to stimuli including light, heat, ultrasound, electrical signals, pH, and oxidative stress; g) diversely sized and colored nanoparticles for imaging, and h) nanowires for retinal prostheses. Additionally, nanofabricated delivery systems including implants, films, microparticles, and nanoparticles are described. Although the above nanomedicines may be administered by various routes including topical, intravitreal, intravenous, transscleral, suprachoroidal, and subretinal routes, each nanomedicine should be tailored for the disease, drug, and site of administration. In addition to the nature of materials used in nanomedicine design, depending on the site of nanomedicine administration, clearance and toxicity are expected to differ.

Molecular basis of the inner blood-retinal barrier and its breakdown in diabetic macular edema and other pathological conditions

Breakdown of the inner endothelial blood-retinal barrier (BRB), as occurs in diabetic retinopathy, age-related macular degeneration, retinal vein occlusions, uveitis and other chronic retinal diseases, results in vasogenic edema and neural tissue damage, causing loss of vision. The central mechanism of altered BRB function is a change in the permeability characteristics of retinal endothelial cells caused by elevated levels of growth factors, cytokines, advanced glycation end products, inflammation, hyperglycemia and loss of pericytes. Subsequently, paracellular but also transcellular transport across the retinal vascular wall increases via opening of endothelial intercellular junctions and qualitative and quantitative changes in endothelial caveolar transcellular transport, respectively. Functional changes in pericytes and astrocytes, as well as structural changes in the composition of the endothelial glycocalyx and the basal lamina around BRB endothelium further facilitate BRB leakage. As Starling's rules apply, active transcellular transport of plasma proteins by the BRB endothelial cells causing increased interstitial osmotic pressure is probably the main factor in the formation of macular edema. The understanding of the complex cellular and molecular processes involved in BRB leakage has grown rapidly in recent years. Although appropriate animal models for human conditions like diabetic macular edema are lacking, these insights have provided tools for rational design of drugs aimed at restoring the BRB as well as for design of effective transport of drugs across the BRB, to treat the chronic retinal diseases such as diabetic macular edema that affect the quality-of-life of millions of patients.

Antiangiogenic therapy with anti-vascular endothelial growth factor modalities for diabetic macular oedema

BACKGROUND

Diabetic macular oedema (DMO) is a common complication of diabetic retinopathy. Although grid or focal laser photocoagulation has been shown to reduce the risk of visual loss in DMO or clinically significant macular oedema (CSMO), vision is rarely improved. Antiangiogenic therapy with anti-vascular endothelial growth factor (anti-VEGF) modalities has recently been proposed for improving vision in people with DMO.

OBJECTIVES

To assess the effectiveness, safety and cost-effectiveness of anti-VEGF therapy for preserving or improving vision in people with DMO.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 6), MEDLINE (January 1946 to June 2012), EMBASE (January 1980 to June 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 13 June 2012.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing any antiangiogenic drugs with an anti-VEGF mechanism of action versus another treatment, sham treatment, or no treatment in patients with DMO. We also included economic evaluations to assess cost-effectiveness.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data. The risk ratio (RR) of visual loss and visual gain of three or more lines was estimated at least six months after treatment. Each economic analysis was described narratively using a structured format.

MAIN RESULTS

Eleven studies provided data on three comparisons of interest in this review. We based our conclusions on the RR of gain or loss of three or more lines of vision at about one year, which was more consistently reported as follow-up.Compared with sham treatment, there was evidence of moderate quality in three studies (497 participants, follow-up 8 to 12 months) that antiangiogenic therapy (pegaptanib: two studies, 246 participants; ranibizumab: one study, 151 participants) doubled and, respectively, halved, the chance of gaining or losing three or more lines of vision (RR: 2.19, 95% confidence interval (CI) 1.36 to 3.53; RR: 0.28, 95% CI: 0.13 to 0.59). In meta-analyses, the benefit was larger for ranibizumab compared to pegaptanib, but no significant subgroup difference could be demonstrated regarding our primary outcome.Compared with grid laser photocoagulation, there was evidence of moderate quality that antiangiogenic therapy (bevacizumab: two studies, 167 participants; ranibizumab: two studies, 300 participants; aflibercept: one study, 221 participants, 89 used for data extraction) more than doubled and, respectively, reduced by at least two thirds, the chance of gaining or losing three or more lines of vision (RR: 3.20, 95% CI 2.07 to 4.95 and RR: 0.13, 95% CI: 0.05 to 0.34, respectively). In meta-analyses, no significant subgroup difference could be demonstrated between bevacizumab, ranibizumab and aflibercept regarding our primary outcome, but, again, there was little power to detect a difference.Compared with grid laser photocoagulation alone, there was high quality evidence that ranibizumab plus photocoagulation (three studies, 783 participants) doubled and, respectively, at least halved, the chance of gaining or losing three or more lines of vision (RR: 2.11, 95% CI 1.67 to 2.67; RR: 0.29, 95% CI: 0.15 to 0.55).Systemic and ocular adverse events were rare in the included studies. Meta-analyses conducted for all antiangiogenic drugs compared with either sham or photocoagulation (nine studies, 104 events in 2159 participants) did not show a significant difference regarding arterial thromboembolic events (RR: 0.85 (0.56 to 1.28). Similarly, no difference was suggested regarding overall mortality (53 events, RR: 0.95 (0.52 to 1.74), but clinically significant differences could not be ruled out.

AUTHORS' CONCLUSIONS

There is moderate quality evidence that antiangiogenic drugs provide a definite, but small, benefit compared to current therapeutic options for DMO, i.e. grid laser photocoagulation, or no treatment when laser is not an option. The quality and quantity of the evidence was larger for ranibizumab, but there was little power to investigate drug differences. Most data were obtained at one year, and a long-term confirmation is needed, since DMO is a chronic condition. Safety of both drug and the intravitreal injection procedure were good in the trials, but further long-term data are needed to exclude small, but clinically important differences regarding systemic adverse events.

Evidence for diffuse central retinal edema in vivo in diabetic male Sprague Dawley rats

Background

Investigations into the mechanism of diffuse retinal edema in diabetic subjects have been limited by a lack of animal models and techniques that co-localized retinal thickness and hydration in vivo. In this study we test the hypothesis that a previously reported supernormal central retinal thickness on MRI measured in experimental diabetic retinopathy in vivo represents a persistent and diffuse edema.

Methodology/Principal Findings

In diabetic and age-matched control rats, and in rats experiencing dilutional hyponatremia (as a positive edema control), whole central retinal thickness, intraretinal water content and apparent diffusion coefficients (ADC, ‘water mobility’) were measured in vivo using quantitative MRI methods. Glycated hemoglobin and retinal thickness ex vivo (histology) were also measured in control and diabetic groups. In the dilutional hyponatremia model, central retinal thickness and water content were supernormal by quantitative MRI, and intraretinal water mobility profiles changed in a manner consistent with intracellular edema. Groups of diabetic (2, 3, 4, 6, and 9 mo of diabetes), and age-matched controls were then investigated with MRI and all diabetic rats showed supernormal whole central retinal thickness. In a separate study in 4 mo diabetic rats (and controls), MRI retinal thickness and water content metrics were significantly greater than normal, and ADC was subnormal in the outer retina; the increase in retinal thickness was not detected histologically on sections of fixed and dehydrated retinas from these rats.

Conclusions/Significance

Diabetic male Sprague Dawley rats demonstrate a persistent and diffuse retinal edema in vivo, providing, for the first time, an important model for investigating its pathogenesis and treatment. These studies also validate MRI as a powerful approach for investigating mechanisms of diabetic retinal edema in future experimental and clinical investigations.

Intravitreal bevacizumab alone versus combined with macular photocoagulation in diabetic macular edema

Purpose

To compare the efficacy between intravitreal bevacizumab and combination treatment (bevacizumab and macular photocoagulation) for the treatment of diabetic macular edema (DME). In addtion, changes of DME type were researched using optical coherence tomography.

Methods

The present study included 90 eyes with bevacizumab injection and 38 eyes with combination treatment. Using chart records, patients were reviewed until 6 months after treatment. The present study compared changes of visual acuity (VA) and macular thickness at each follow up. DME was classified into 4 types and the morphologic pattern was compared.

Results

In patients with the bevacizumab injection only, VA improved from 0.29 ± 0.18 to 0.48 ± 0.26 at 1 month and returned to 0.32 ± 0.20 at 6 months after treatment. In the combination treatment, VA improved from 0.32 ± 0.22 to 0.52 ± 0.26 at 1 month and returned to 0.36 ± 0.18 at 6 months after treatment. There was no significant improvement of VA at the final follow-up with either treatment. There was significant decrease of macular thickness except in the mixed DME type.

Conclusions

The combination treatment did not yield better VA or macular thickness reduction at 6 months than bevacizumab injection alone. By classifying and observing the change of DME type, determining the treatment objectively and predicting the effectiveness of treatment can be helpful.

Antiangiogenic therapy with anti-vascular endothelial growth factor modalities for diabetic macular oedema

BACKGROUND

Diabetic macular oedema (DMO) is a common complication of diabetic retinopathy. The retina at the macula thickens and this can cause gradual loss of central vision. Although grid or focal laser photocoagulation has been shown to reduce the risk of visual loss in DMO or clinically significant macular oedema (CSMO), vision is rarely improved. Antiangiogenic therapy with anti-vascular endothelial growth factor (anti-VEGF) modalities has recently been proposed for improving vision in people with DMO. Anti-VEGF drugs are delivered by an injection in the vitreous cavity of the eye.

OBJECTIVES

This review aims to assess the effectiveness of anti-VEGF therapy for preserving or improving vision in people with DMO.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE and Caribbean Literature on Health Sciences (LILACS). There were no language or date restrictions in the search for trials.The electronic databases were last searched on 16 April 2009.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing any antiangiogenic drugs with an anti-VEGF mechanism of action compared to another treatment, sham treatment, or no treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data. The risk ratio (RR) of visual loss and visual gain of 3 or more lines was estimated at least six months after treatment.

MAIN RESULTS

We found four small studies that collected only short-term outcomes (24 to 36 weeks); three of which had more than two randomisation groups generating five types of comparisons overall. Only one comparison included more than one trial in the analysis. The short-term outcome was the mean change in LogMAR visual acuity. One study on 172 patients compared three doses of pegaptanib versus sham (about 5 injections on average) and another compared bevacizumab or bevacizumab plus triamcinolone with sham (multiple bevacizumab injections and a single triamcinolone injection in 101 patients, 115 eyes overall) in patients with CSMO that was refractory to photocoagulation. Bevacizumab or bevacizumab plus triamcinolone were also compared to photocoagulation in 129 patients with untreated CSMO (150 eyes, multiple injections needed in 24 patients). Although comparisons tended to favour antiangiogenic therapy, estimates did not reach statistical significance or, if they did, they were not robust to sensitivity analysis regarding missing data and potential bias related to single trial estimates. No difference could be demonstrated in one study on 26 patients comparing bevacizumab to triamcinolone (both administered with a single injection) and between bevacizumab and bevacizumab plus triamcinolone in two studies on 182 patients. All the studies in this review, except for the study on pegaptanib, were at risk of bias based on the assessment of six methodological quality items.There were no serious adverse effects in these short-term studies, except for one case of severe anterior uveitis in one eye treated with bevacizumab. No included study examined long-term adverse effects of antiangiogenic therapy.

AUTHORS' CONCLUSIONS

There is not sufficient high quality evidence from large RCTs supporting the use of either single or multiple anti-VEGF intravitreal injections to treat DMO. Results from ongoing studies on several compounds should assess not only treatment efficacy but also, if a benefit is found, the number of injections needed for maintenance and long-term safety.

Intravitreal steroids for macular edema in diabetes

BACKGROUND

Macular edema is secondary to leakage from diseased retinal capillaries and is an important cause of poor central visual acuity in patients with diabetic retinopathy.

OBJECTIVES

This review evaluated the effectiveness and safety of intraocular steroids in treating diabetic macular edema (DME).

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE in June 2007, reference lists, Science Citation Index and conference proceedings.

SELECTION CRITERIA

We included randomized clinical trials (RCTs) evaluating any form of intravitreal steroids for treating DME.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility, methodological quality and extracted data. We performed meta-analyses when appropriate.

MAIN RESULTS

Seven studies, involving 632 DME eyes were included. Four examined the effectiveness of intravitreal triamcinolone acetate injection (IVTA), three examined intravitreal steroids implantation (fluocinolone acetonide implant (FAI) or dexamethasone drug delivery system (DDS)). Two trials were at low risk of bias, one was at median risk of bias, two were at high risk of bias and the remaining two were at unclear risk of bias. The preponderance of data suggest a beneficial effect from IVTA. Comparing IVTA with controls, the mean difference in visual acuity was -0.15 LogMAR (95% CI -0.21 to -0.09) at 3 months (based on three trials), -0.23 LogMAR (95% CI -0.33 to -0.13) at 6 months (two trials), -0.29 LogMAR (95% CI -0.47 to -0.11) at 9 months (one trial), and -0.11 LogMAR (95% CI -0.20 to -0.03) at 24 months (one trial), all in favor of IVTA. The relative risk (RR) for one or more lines improvement in visual acuity was 2.85 (95% CI 1.59 to 5.10) at 3 months (two trials), 1.25 (95% CI 0.66 to 2.38) at 6 months (one trial), and 2.17 (95% CI 1.15 to 4.11) at 24 months (one trial), all in favor of IVTA. We did not find evidence for three or more lines improvement in visual acuity. The mean difference in retinal thickness was -131.97 um (95% CI -169.08 to -94.86) at 3 months (two trials), -135.00 um (95% CI -194.50 to -75.50) at 6 months (one trial), -133.00 um (95% CI -199.86 to -66.14) at 9 months (one trial), and -59.00 um (95% CI -103.50 to -14.50) at 24 months (one trial), all in favor of IVTA. The RR for at least one grade macular edema resolution was 5.15 (95% CI 2.23 to 11.88) at 3 months in favor of IVTA (one trial). Two trials reported improved clinical outcome when FAI was compared to standard of care. Beneficial effect was also observed in one dexamethasone DDS trial. Increased intraocular pressure and cataract formation were side effects requiring monitoring and management.

AUTHORS' CONCLUSIONS

RCTs included in this review suggest that steroids placed inside the eye by either intravitreal injection or surgical implantation may improve visual outcomes in eyes with persistent or refractory DME. Since the studies in our report focused on chronic or refractory DME, the question arises whether intravitreal steroids therapy could be of value in other stages of DME, especially the earlier stages either as standalone therapy or in combination with other therapies, such as laser photocoagulation.

Diabetic macular edema and its relationship to renal microangiopathy: a sample of Type I diabetes mellitus patients in a 15-year follow-up study

PURPOSE

In the present study, our objective was to determine the epidemiological risk factors for the development of diabetic macular edema, especially attendant on renal diabetic lesion (microalbuminuria or overt nephropathy) in 112 Type I diabetic patients after 15 years.

METHODS

This is a 15-year follow-up study of a cohort of 112 consecutive Type I (insulin-dependent) diabetes mellitus patients without diabetic retinopathy or nephropathy who were enrolled in 1990. We studied the incidence of diabetic macular edema and its risk factors. The epidemiological risk factors included in the study were as follows: gender, diabetes duration, glycated hemoglobin (HbA1c) levels, arterial hypertension, macroangiopathy, triglyceride levels, fractions of cholesterol [high-density lipoprotein cholesterol and low-density lipoprotein (LDL) cholesterol], and cigarette smoking.

RESULTS

The incidence of diabetic macular edema after 15 years was as follows: the focal form of diabetic macular edema was present in 13 (11.6%) patients and the diffuse form of macular edema was present in 10 (8.9%) patients, among 23 (20.5%) patients. The following factors were significant in the development of diabetic macular edema: high levels of LDL-cholesterol (P=.013), high levels (>7.5%) of HbA1c (P=.021), the presence of macroangiopathy (P=.022), the severity of diabetic retinopathy (P=.029), the presence of arterial hypertension (P=.037), and the presence of overt nephropathy (P=.047). Microalbuminuria was not significant in logistic regression (P=.587), and cigarette smoking was not significant (P=.976). The relationship between diabetic macular edema and duration of diabetes presented two peaks of incidence: first in patients with 15-20 years' duration of diabetes mellitus, and second in patients with >35 years' duration.

CONCLUSIONS

In summary, our data suggest that better control of glycemia, LDL-cholesterol levels, and blood pressure in Type I diabetes mellitus patients may be beneficial in reducing the incidence of diabetic macular edema. Finally, our data validate the current guidelines for ophthalmologic care for the detection of diabetic macular edema over the long-term course of diabetes.

Signaling and functions of angiopoietin-1 in vascular protection

Angiopoietin-1 (Ang1) has powerful vascular protective effects: suppressing plasma leakage, inhibiting vascular inflammation, and preventing endothelial death. Preclinical studies indicate that Ang1 may be therapeutically useful in a number of situations, including treatment of edema, endotoxemia, and transplant arteriosclerosis. However, the ligand has also been implicated in vessel remodeling, induction of angiogenesis and pulmonary hypertension, indicating that strategies to minimize any deleterious effects while optimizing vessel protection are likely to be needed. This review surveys the published data on vascular protective effects of Ang1 and highlights the therapeutic potential of this ligand, as well as possible limitations to its use. We also consider the data on Ang1 receptors and speculate on how to maximize therapeutic benefit by targeting the Tie receptors.

Mechanisms of chloride influx during KCl-induced swelling in the chicken retina

An increase in extracellular KCl ([KCl]o) occurs under various pathological conditions in the retina, leading to retinal swelling and possible neuronal damage. The mechanisms of this KCl o-induced retinal swelling were investigated in the present study, with emphasis on the Cl- transport mechanisms. Increasing [KCl]o (from 5 to 70 mM) led to concentration-dependent swelling in chicken retinas. The curve relating the degree of swelling to [KCl]o was biphasic, with one component from 5 to 35 mM [KCl]o and another from 35 to 100 mM. As Cl- omission prevented swelling in all conditions, the effect of cotransporter or Cl- channel blockers was examined to investigate the mechanisms of Cl- influx. The cotransporter blockers bumetanide and DIOA reduced swelling by 68% and 76%, respectively at [KCl]o 25 mM (K25), and by 14-17% at [KCl]o 54 mM (K54). The Cl- channel blockers NPPB and niflumic acid did not affect swelling at K25 but reduced it by 90-95% at K54 (NPPB IC50 60.7 microM). Furosemide showed an atypical effect, decreasing swelling by 14% at K25 and by 95% at K54 (IC50 173.9 microM). Na+ omission decreased swelling at K25 but not at K54. These results suggest the contribution of cotransporters to Cl- influx at K25 and of Cl- channels at K54. At K25, swelling was found in the ganglion cell layer and in the lower half of the inner nuclear layer. With K54, swelling occurred in all inner retinal layers. The ganglion cell layer swelling was due to both Muller cell end-foot and ganglion cell soma swelling. K54 also induced ganglion cell damage as shown by disorganized, pyknotic and refringent nuclei.

Risk factors for diffuse and focal macular edema

OBJECTIVE

The epidemiological risk factors for the different forms of diabetic macular edema (focal or diffuse) are not differentiated in the literature. In the present study, the objective was to determine which risk factors influence the appearance of focal or diffuse macular edema. RESEARCH, DESIGN, AND METHODS: A 4-year prospective study in a population of Type II diabetic patients (NIDDM) in three groups, the first with 29 patients with diffuse diabetic macular edema (Group A), the second with 32 patients with focal macular edema (Group B), and the third with 32 patients with diabetic retinopathy but without diabetic macular edema (Group C); the three groups were selected on the basis of sex, age, and duration of diabetes with similar patterns. We studied the following risk factors: treatment of diabetes mellitus by insulin, presence of diastolic blood hypertension, presence of microalbuminuria or diabetic nephropathy, levels of HbA1c, type of diabetic retinopathy, presence of previous panretinal photocoagulation, and levels of triglycerides and fractions of cholesterol.

RESULTS

In discriminant analysis and in order of importance, the epidemiological risk factors for Group A were the following: presence of panretinal laser, diastolic blood hypertension, diabetic nephropathy, and insulin treatment; for group B, the risk factors were the following: insulin treatment, presence of diastolic blood hypertension, and high levels of glycated haemoglobin (HbA1c); and for group, C the risk factors were the following: diastolic blood hypertension, insulin treatment of diabetes, and high levels of HbA1c.

CONCLUSIONS

In the present study, the group of patients with focal macular edema were epidemiologically similar to the group of patients with diabetic retinopathy without macular edema, the group of patients with diffuse macular edema were epidemiologically different.

The correlation between fluorescein angiographic and optical coherence tomographic features in clinically significant diabetic macular edema

PURPOSE

To assess the correlation between the features of optical coherence tomography (OCT) and fluorescein angiography in clinically significant diabetic macular edema.

DESIGN

Retrospective observational case series.

METHODS

This study involved 145 eyes (91 patients) with clinically significant diabetic macular edema. The fluorescein angiography features were categorized into focal leakage type, diffuse leakage type, and diffuse cystoid leakage type. The OCT features were categorized into four types: type 1, thickening with homogeneous optical reflectivity; type 2, thickening with markedly decreased optical reflectivity in the outer retinal layer; type 3A, foveolar detachment without traction; and type 3B, foveolar detachment with apparent vitreofoveal traction. The correlation between fluorescein angiography types and OCT types were analyzed, and their associations with visual acuity, central foveal thickness. and stages of diabetic retinopathy were evaluated.

RESULTS

The prevalence of OCT type 1 was higher in the focal leakage type (73.0%) and in the diffuse leakage type (58.9%) than in the diffuse cystoid leakage type (3.8%) of fluorescein angiography (P <.0001). The prevalence of OCT type 2 and 3A was higher in the diffuse cystoid leakage type (57.7% and 34.6%, respectively) than in the focal leakage type (20.6% and 3.2%) or diffuse leakage type(28.6% and 10.7%; P <.0001). The stages of retinopathy correlated with fluorescein angiography types (P =.016). Optical coherence tomography type 1 and the focal leakage type of fluorescein angiography showed the least foveal thickness and the best visual acuity (P <.05).

CONCLUSIONS

There was a significant correlation between the features of OCT and fluorescein angiography in clinically significant diabetic macular edema. The combined data from both OCT and fluorescein angiography may provide a clearer understanding of the anatomic and physiologic characteristics of clinically significant diabetic macular edema.

Prognostic impact of vascular leakage in acute Kawasaki disease

BACKGROUND

Increased microvascular permeability is an initial step of Kawasaki disease (KD). We reported that vascular endothelial growth factor (VEGF) might play a role in the vascular leakage of KD. In fatal KD, plasma leakage was extensively documented at VEGF-positive microvessels. Increases in vascular leakage cause hypoalbuminemia and noncardiogenic edema. However, the prognostic impact of vascular leakage in KD remains unclear.

METHODS AND RESULTS

We compared 76 patients who became afebrile within 5 days after starting intravenous gamma globulin (IVGG) (2 g/kg over 5 days) (IVGG-responsive) with 27 patients who did not respond (IVGG-resistant). Baseline levels of serum VEGF and albumin were similar between the groups. After IVGG, VEGF levels increased (P<0.0001) and albumin levels decreased (P<0.00001) in both groups. However, the IVGG-resistant group had higher VEGF levels (P=0.029) and severe hypoalbuminemia (P<0.00001) compared with the IVGG-responsive group. Coronary aneurysms were documented in 12 patients from the IVGG-resistant group but not in the IVGG-responsive group. Then IVGG-resistant patients were divided into 2 subgroups according to the presence (n=12) or absence (n=15) of coronary aneurysms. There was no difference between subgroups in age, sex, laboratory data including albumin, and retreated doses of IVGG. However, body weight gain after IVGG was documented in patients who subsequently developed coronary aneurysms (P=0.003) but not in those who did not (P=0.967).

CONCLUSIONS

These results suggest that vascular leakage may be a key feature of KD pathophysiology. The present study may provide better insights into the pathogenesis and treatment of patients resistant to IVGG in acute KD.

Determination of aldose reductase activity in the eye by localized magnetic resonance spectroscopy

The polyol pathway plays an important role in the formation of diabetic complications of the eye. Due to variations in the pharmacokinetic properties of aldose reductase inhibitors and variations in the degradation of the blood-ocular barrier, it is often difficult to determine the proper intraocular levels of aldose reductase inhibitor required for inhibition of aldose reductase activity in ocular tissues. Utilizing localized magnetic resonance spectroscopy (MRS), the present method can determine adequate inhibition of aldose reductase activity in the lens by noninvasively measuring polyol pathway activity in the eye. New Zealand White rabbits, under anesthesia, were administered an intravitreal injection of 3-fluoro-3-deoxy-D-glucose (3FDG). Localized MRS was then used to assess polyol pathway activity by determining the levels of 3-fluoro-3-deoxy-D-sorbitol (3FS) and 3-fluoro-3-deoxy-D-fructose (3FF) metabolite formation from 3FDG in the eye. MRS was able to follow the loss of 3FDG from the vitreous into the anterior segment of the eye and particularly into the lens and aqueous. The primary metabolism of 3FDG observed by MRS was the formation of 3FS in the lens that is catalyzed by aldose reductase. Production of 3FS was linear in time and decreased with the oral administration of an aldose reductase inhibitor.

Leakage-resistant blood vessels in mice transgenically overexpressing angiopoietin-1

Angiopoietin-1 (Ang1) and vascular endothelial growth factor (VEGF) are endothelial cell-specific growth factors. Direct comparison of transgenic mice overexpressing these factors in the skin revealed that the VEGF-induced blood vessels were leaky, whereas those induced by Ang1 were nonleaky. Moreover, vessels in Ang1-overexpressing mice were resistant to leaks caused by inflammatory agents. Coexpression of Ang1 and VEGF had an additive effect on angiogenesis but resulted in leakage-resistant vessels typical of Ang1. Ang1 therefore may be useful for reducing microvascular leakage in diseases in which the leakage results from chronic inflammation or elevated VEGF and, in combination with VEGF, for promoting growth of nonleaky vessels.