RETINAL VASCULAR CYSTOID MACULAR EDEMA: Review and New Theory

Retinal fluid changes and therapeutic effects in symptomatic circumscribed choroidal hemangioma patients: a long-term follow up study

Background

Changes in retinal fluid patterns associated with circumscribed choroidal hemangioma (CCH) have not been investigated yet. A long-term follow-up study was performed to evaluate the changes of retinal fluid patterns and treatment responses.

Methods

We retrospectively reviewed medical records of all CCH patients diagnosed between November 2005 and March 2017. Enrolled patients had visual symptoms, were treatment-naïve, and had been followed-up for more than 2 years. Best corrected visual acuities (BCVA) and the presence, severity, and pattern change of the subretinal fluid (SRF) and intraretinal fluid (IRF) in the macula on optical coherence tomography (OCT) were analyzed at initial presentation and follow-up visits.

Results

Twenty-six patients were enrolled. All patients received one or more of the following treatments: PDT, TTT, and intravitreal bevacizumab (Avastin) injection (IVB). Primary therapy consisted of PDT in 9 patients (34.6%), TTT in 7 patients (26.9%) and IVB in 10 patients (38.5%). At initial presentation, the SRF-only pattern was mostly observed. Despite treatment, IRF occurred over time; eventually, advanced cystoid macular oedema (CME) developed. In terms of retinal fluid reduction, PDT was most efficacious (9/9, 100%), and TTT and IVB showed moderate efficacy (TTT: 4/7, 57.1%; IVB: 5/10, 50%) as a primary therapy. After advanced CME developed, IVB and TTT showed no or minimal effect (TTT: 0/1, 0%; IVB: 0/19, 0%), and PDT was the only effective therapy (6/10, 60%).

Conclusion

The pattern of retinal fluid accompanied by CCH evolved from an SRF-only pattern initially to an advanced CME pattern. The effectiveness of treatments decreased over time, and advanced CME generally showed resistance to treatments. PDT would be the most recommended treatment.

Angiopoietin-4-dependent venous maturation and fluid drainage in the peripheral retina

The maintenance of fluid homeostasis is necessary for function of the neural retina; however, little is known about the significance of potential fluid management mechanisms. Here, we investigated angiopoietin-4 (Angpt4, also known as Ang3), a poorly characterized ligand for endothelial receptor tyrosine kinase Tie2, in mouse retina model. By using genetic reporter, fate mapping, and in situ hybridization, we found Angpt4 expression in a specific sub-population of astrocytes at the site where venous morphogenesis occurs and that lower oxygen tension, which distinguishes peripheral and venous locations, enhances Angpt4 expression. Correlating with its spatiotemporal expression, deletion of Angpt4 resulted in defective venous development causing impaired venous drainage and defects in neuronal cells. In vitro characterization of angiopoietin-4 proteins revealed both ligand-specific and redundant functions among the angiopoietins. Our study identifies Angpt4 as the first growth factor for venous-specific development and its importance in venous remodeling, retinal fluid clearance and neuronal function.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF ACUTE MACULAR NEURORETINOPATHY REVEALS DEEP CAPILLARY ISCHEMIA

PURPOSE

To present the multimodal retinal imaging findings, including optical coherence tomography (OCT) angiography, of an atypical case of acute macular neuroretinopathy (AMN).

METHODS

The multimodal retinal imaging findings, including structural OCT and OCT angiography, of an atypical case of AMN are presented.

RESULTS

A 23-year old woman, with a history of an unrelenting sinusitis treated with prednisone therapy and decongestants, presented with an acute scotoma of the right eye. Structural OCT illustrated an area of hyperreflectivity in the outer plexiform and outer nuclear layers nasal to the fovea, with associated disruption of the inner segment ellipsoid band consistent with AMN. At the 2-week follow-up visit, intraretinal fluid was noted with repeat OCT, with spontaneous resolution of the fluid at the 2-month follow-up visit. Optical coherence tomography angiography illustrated a flow void in the deep retinal capillary plexus associated with the AMN lesion.

CONCLUSION

Atypical findings of AMN are presented in this case report including the presence and spontaneous resolution of intraretinal fluid. Although OCT angiography illustrated a flow deficit within the deep retinal capillary plexus, the cause of AMN remains elusive.

Characteristics of diabetic macular edema on optical coherence tomography may change over time or after treatment

Purpose

To investigate optical coherence tomography (OCT) characteristics in diabetic macular edema (DME) over time and after treatment.

Patients and methods

OCT morphological features in DME eyes treated with ranibizumab with at least 1 year of follow-up were retrospectively analyzed.

Results

Thirty-five eyes were included. From baseline to Month 12, mean visual gain was 7.2±13.6 letters and mean central retinal thickness reduction was 61.9±121.8 μm. Fovea-involving ellipsoid zone (EZ) disruption was significantly associated with final vision of <70 letters. Subretinal fluid at baseline was present only in eyes naïve to previous intravitreal pharmacotherapy and was related to better visual gain and fewer injections. Treatment-naïve eyes had shorter DME duration and less EZ damage.

Conclusion

DME characteristics on OCT may change over time or after treatment. Subretinal fluid may be associated with earlier change and less EZ damage in DME.

TO PEEL OR NOT TO PEEL THE INTERNAL LIMITING MEMBRANE IN IDIOPATHIC EPIRETINAL MEMBRANES

BACKGROUND

Epiretinal membranes (ERMs) have been described for more than 150 years. Currently, they are a common indication for vitreoretinal surgery. Recently, there has been an increasing trend to peel the internal limiting membrane (ILM). Although ILM peeling has generally been accepted as a fundamental step in macular hole repair, its current role in ERM remains controversial.

METHODS

Literature review.

RESULTS

Proponents of ILM peeling argue that peeling of the ILM reduces the recurrence rate and facilitates a greater resolution of retinal folds. Opponents of ILM peeling show that the visual outcomes between eyes that undergo ILM peeling and those that do not have their ILM peeled are the same. Stripping of the ILM removes the Müller cell footplates, so it is reasonable to expect some Müller cell dysfunction. Adverse events such as eccentric paracentral macular holes, macular microscotomata, and retinal dimpling have been associated with ILM peeling.

CONCLUSION

Internal limiting membrane peeling does not improve the functional outcomes after ERM surgery. Internal limiting membrane peeling reduces ERM recurrences, but many recurrences are not clinically significant. It remains unclear what the long-term effects of ILM peeling are. We should err on the side of caution and avoid routine ILM peeling in primary idiopathic ERM cases and should reserve it for recurrent and high risk of recurrence cases.

Evaluation of systemic risk factors in different optical coherence tomographic patterns of diabetic macular edema

AIM

To elucidate the relationship between systemic risk factors and different patterns of diabetic macular edema (DME) determined with optical coherence tomography (OCT).

METHODS

In this cross-sectional study, DME was classified by OCT as diffuse retinal thickness (DRT), cystoid macular edema (CME) and serous retinal detachment (SRD) and the relationship between the systemic risk factors and DME patterns was evaluated.

RESULTS

Of the 57 patients with DME, 21 (36.8%) had DRT, 24 (42.1%) had CME and 12 (21.0%) had SRD. Micro- or macro-albuminuria was significantly higher in the DRT pattern (61.9%) compared with the SRD (50.0%) and CME patterns (25.0%; P=0.040). Hemoglobin A1c (HbA1c) level was significantly higher and patients were younger in the DRT pattern group (P=0.034, P=0.032). Best corrected visual acuity was the worst and central macular thickness was the thickest in the CME pattern group.

CONCLUSION

Micro- or macro-albuminuria may be more frequent and HbA1c level may be higher in patients with DRT. These patients are also seen to be younger than patients with non-DRT.

BETTER PROGNOSIS FOR EYES WITH PRESERVED FOVEAL DEPRESSION AFTER INTRAVITREAL RANIBIZUMAB INJECTION FOR MACULAR EDEMA SECONDARY TO CENTRAL RETINAL VEIN OCCLUSION

PURPOSE

To determine the prognosis of eyes with central retinal vein occlusion that had a preserved foveal depression at the baseline and were treated by intravitreal ranibizumab injections (IRIs).

METHODS

The authors reviewed the medical records of 23 eyes of 23 consecutive treatment-naive patients who received IRIs to treat the macular edema due to central retinal vein occlusion. Eyes were classified by the pre-IRI presence or absence of a foveal depression. A foveal depression was defined as a central foveal thickness that was <50 μm thinner than the average thickness at 200 μm temporal and nasal to the central fovea. The characteristics of the two groups were compared.

RESULTS

Seven of 23 eyes had a preserved foveal depression before the IRI. The mean number of injections within 12 months after the initial IRI was significantly fewer (P < 0.001) in eyes with foveal depression (1.6 ± 0.5) than in eyes without foveal depression (4.3 ± 1.3). The mean best-corrected visual acuity at 12 months after the initial IRI was significantly better (P = 0.003) in eyes with foveal depression (0.10 ± 0.17 logarithm of the minimum angle of resolution [logMAR] units; 20/25 Snellen units) than in eyes without foveal depression (0.77 ± 0.54 logMAR units; 20/118 Snellen units).

CONCLUSION

These results indicate that the prognosis is better for eyes with a foveal depression before the IRI treatment for a macular edema secondary to central retinal vein occlusion.

DEXAMETHASONE INTRAVITREAL IMPLANT FOR THE TREATMENT OF RECALCITRANT MACULAR EDEMA AFTER RHEGMATOGENOUS RETINAL DETACHMENT REPAIR

PURPOSE

To investigate the efficacy of the intravitreal dexamethasone implant as the treatment for recalcitrant macular edema after successful rhegmatogenous retinal detachment repair.

METHODS

A retrospective review of the medical records was performed on 17 consecutive patients (17 eyes) with recalcitrant macular edema associated with rhegmatogenous retinal detachment repair who were treated with a single or multiple injections of an intravitreal dexamethasone 0.7-mg implant (Ozurdex; Allergan Inc) at two centers. Main outcomes of the study were change in logarithm of the minimum angle of resolution visual acuity, measurement of central foveal thickness, and macular cube volume as measured by spectral domain optical coherence tomography and frequency of complications.

RESULTS

The mean age was 67 years (range, 51-78 years). All 17 patients received previous topical therapy and 12 of them had previous administration of intravitreal triamcinolone with persistence of macular edema. Baseline mean best-corrected visual acuity was 20/100 (logarithm of the minimum angle of resolution 0.75; range, 0.18-1.3 ±0.37) in the affected eyes. There was a statistically significant improvement in best-corrected visual acuity at 1 month (P < 0.001) and 3 months (P = 0.01). Mean baseline central foveal thickness was 505 μm, and mean macular cube volume was 10.62 mm. There was a statistically significant decrease in central foveal thickness and macular cube volume at 1 month (505-290 μm, P = 0.013 and 10.62-9.13 mm, P < 0.0001) and 3 months (P = 0.01). All patients developed recurrence of macular edema at 3 months, which required retreatment. The average number of implants was 4 (range, 1-14). No adverse effects such as retinal detachment or endophthalmitis occurred. Two patients experienced an increase in intraocular pressure that was controlled with topical therapy.

CONCLUSION

Macular edema that occurs in eyes after successful repair of rhegmatogenous retinal detachment can be chronic and recalcitrant, and may be successfully and safely treated with the dexamethasone intravitreal implant.

Optical Coherence Tomography Angiography in Eyes with Retinal Vein Occlusion

Optical coherence angiography (OCTA) is a noninvasive technique that has been introduced in recent years to detect ophthalmological pathology. The growing usage of OCTA to detect retinal abnormalities can be attributed to its advantages over the reference-standard fluorescein angiography (FA), although both of these techniques can be used in association. OCTA's advantages include its dye independency, its ability to produce depth-resolved images of retinal and choroidal vessels that yield images of different vascular layers of the retina, and the better delineation of the foveal avascular zone. OCTA's disadvantages include the lack of normalized patient data, artefactual projection issues, and its inability to detect low-flow lesions or pathologic conditions. Different OCTA platforms use unique algorithms to detect microvasculature, which are implemented in both spectral-domain (SD) and swept-source (SS) OCT machines. Microvascular changes in retinal vein occlusions (RVOs) are visible in both the superficial and deep capillary networks of the retina in OCTA. These visualizations include a decrease in foveal and parafoveal vascular densities, non-perfusion areas, capillary engorgement and telangiectasias, vascular tortuosity, microaneurysms, disruption of the foveal perivascular plexus, and formation of collateral vessels. The restricted field of view and inability to show leakage are important limitations associated with the use of OCTA in RVO cases. In this article, we present a brief overview of OCTA and a review of the changes detectable in different slabs by OCTA in RVO cases published in PubMed and Embase.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

Wogonin prevents TLR4-NF-κB-medicated neuro-inflammation and improves retinal ganglion cells survival in retina after optic nerve crush

Chronic neuro-inflammation is involved in the death of retinal ganglion cells (RGCs) in glaucoma. The aim of this study is to determine whether wogonin can suppress inflammatory responses and rescue RGCs death after optic nerve crush (ONC), an ideal animal model of glaucoma. Wogonin was administered intraperitoneally 10 min after establishment of ONC model. In this study, wogonin treatment reduced RGCs loss and inhibited RGCs apoptosis demonstrated by the increased Brn3a labeling RGCs at day 14 and the decreased cleaved caspase-3 expression at day 7 after ONC, respectively. In ONC model, number of GFAP-positive glial cells and iba1-positive microglial cells were increased, combined of the elevated level of pro-inflammatory cytokines released in retina at day 7. However, most of these responses were inhibited after wogonin treatment. The level of TLR4 expression, NF-κB-P65 nucleus location and NF-κB-P65 phosphorylation were increased in retina at day 1 after ONC, which was significantly reduced after wogonin treatment. These results demonstrated that wogonin protected RGCs survival and suppressed neuro-inflammation in retina after ONC by inhibiting TLR4-NF-κB pathways. We conclude that wogonin could be a possible strategy for the treatment of glaucoma.

Optical coherence tomography angiography in pseudophakic cystoid macular oedema compared to diabetic macular oedema: qualitative and quantitative evaluation of retinal vasculature

AIMS

To describe optical coherence tomography angiography (OCT-A) abnormalities of patients with pseudophakic cystoid macular oedema (PCMO) before and after pharmacological resolution, compared with diabetic macular oedema (DMO) and normal eyes.

METHODS

In this retrospective, observational study, 44 eyes (30 patients) were included: 15 eyes (15 patients) affected by PCMO; 14 healthy fellow eyes used as negative control group; 15 eyes (15 age-matched and sex-matched patients) with DMO used as positive control group. All patients underwent a complete ophthalmological examination at baseline, including OCT-A scans of the macula through AngioPlex CIRRUS-5000 (Carl Zeiss Meditec, Dublin, USA). Patients with PCMO and DMO were re-evaluated after the pharmacological resolution of cystoid macular oedema (CMO).

RESULTS

Disruption of parafoveal capillary arcade and cystoid spaces in deep capillary plexus (DCP) were frequent in patients with PCMO and DMO (73% and 100%, 87% and 100%). Capillary abnormalities and non-perfusion greyish areas in DCP were more frequent in DMO (P<0.001 and P=0.014). Patients with PCMO showed a larger foveal avascular zone area in DCP at baseline (P<0.001), which significantly reduced after treatment (P=0.001). Vessel density of full-thickness retina and DCP was reduced in patients with PCMO (P=0.022 and P=0.001), and no changes were observed after treatment. Interestingly, DCP appeared less represented in patients with DMO than PCMO subjects (P=0.001).

CONCLUSIONS

Patients with PCMO have an impairment of mainly DCP, partially reversible after treatment. Furthermore, we disclosed that different alterations of the retinal vasculature characterise CMO derived from two different diseases, namely PCMO and DMO, and this could be due to their distinct pathophysiology.

Diabetic Macular Edema: Current Understanding, Pharmacologic Treatment Options, and Developing Therapies

Diabetic retinopathy and diabetic macular edema comprise a major source of visual disability throughout the developed world. The etiology and pathogenesis of macular edema is intricate and multifactorial, in which the hyperglycemic state in diabetes induces a microangiopathy. Through several inflammatory and vasogenic mediators, including vascular endothelial growth factor (VEGF) upregulation and inflammatory cytokines and chemokines, pathologic changes are induced in the vascular endothelium triggering breakdown of the blood retinal barrier, causing extravasation of fluid into the extracellular space and manifesting clinically as macular edema, resulting in visual loss. The advent of medications targeting the VEGF pathway has led to great clinical improvements compared with the previous standard of care of laser therapy alone, as shown in studies such as RISE, RIDE, VIVID, VISTA, and DRCR. However, analyses have shown that many patients have inadequate response or are nonresponders to anti-VEGF therapy, demonstrating the need for additional therapies to more comprehensively treat this disease. Although corticosteroid treatments and implants have demonstrated some efficacy in adjunctive and supplemental treatment, the need to more adequately treat macular edema remains. Our knowledge of diabetic macular edema continues to grow, leading to new currently available and emerging pharmacotherapies to further enhance our treatment and restore vision in those affected by diabetic macular edema. This review will discuss the pathogenesis of diabetic macular edema and the pharmacologic therapies available for its treatment, including anti-VEGF, steroids, and newer therapies still in development, such as angiopoietin antagonists, Tie2 agonists, kallikrein inhibitors, interleukin inhibitors, and others.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Retinal layer segmentation in multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Structural retinal imaging biomarkers are important for early recognition and monitoring of inflammation and neurodegeneration in multiple sclerosis. With the introduction of spectral domain optical coherence tomography (SD-OCT), supervised automated segmentation of individual retinal layers is possible. We aimed to investigate which retinal layers show atrophy associated with neurodegeneration in multiple sclerosis when measured with SD-OCT.

METHODS

In this systematic review and meta-analysis, we searched for studies in which SD-OCT was used to look at the retina in people with multiple sclerosis with or without optic neuritis in PubMed, Web of Science, and Google Scholar between Nov 22, 1991, and April 19, 2016. Data were taken from cross-sectional cohorts and from one timepoint from longitudinal studies (at least 3 months after onset in studies of optic neuritis). We classified data on eyes into healthy controls, multiple-sclerosis-associated optic neuritis (MSON), and multiple sclerosis without optic neuritis (MSNON). We assessed thickness of the retinal layers and we rated individual layer segmentation performance by random effects meta-analysis for MSON eyes versus control eyes, MSNON eyes versus control eyes, and MSNON eyes versus MSON eyes. We excluded relevant sources of bias by funnel plots.

FINDINGS

Of 25 497 records identified, 110 articles were eligible and 40 reported data (in total 5776 eyes from patients with multiple sclerosis [1667 MSON eyes and 4109 MSNON eyes] and 1697 eyes from healthy controls) that met published OCT quality control criteria and were suitable for meta-analysis. Compared with control eyes, the peripapillary retinal nerve fibre layer (RNFL) showed thinning in MSON eyes (mean difference -20·10 μm, 95% CI -22·76 to -17·44; p<0·0001) and in MSNON eyes (-7·41 μm, -8·98 to -5·83; p<0·0001). The macula showed RNFL thinning of -6·18 μm (-8·07 to -4·28; p<0·0001) in MSON eyes and -2·15 μm (-3·15 to -1·15; p<0·0001) in MSNON eyes compared with control eyes. Atrophy of the macular ganglion cell layer and inner plexiform layer (GCIPL) was -16·42 μm (-19·23 to -13·60; p<0·0001) for MSON eyes and -6·31 μm (-7·75 to -4·87; p<0·0001) for MSNON eyes compared with control eyes. A small degree of inner nuclear layer (INL) thickening occurred in MSON eyes compared with control eyes (0·77 μm, 0·25 to 1·28; p=0·003). We found no statistical difference in the thickness of the combined outer nuclear layer and outer plexiform layer when we compared MSNON or MSON eyes with control eyes, but we found a small degree of thickening of the combined layer when we compared MSON eyes with MSNON eyes (1·21 μm, 0·24 to 2·19; p=0·01).

INTERPRETATION

The largest and most robust differences between the eyes of people with multiple sclerosis and control eyes were found in the peripapillary RNFL and macular GCIPL. Inflammatory disease activity might be captured by the INL. Because of the consistency, robustness, and large effect size, we recommend inclusion of the peripapillary RNFL and macular GCIPL for diagnosis, monitoring, and research.

FUNDING

None.

Microcystoid Macular Changes in Association With Idiopathic Epiretinal Membranes in Eyes With and Without Glaucoma: Clinical Insights

PURPOSE

To describe the clinical and surgical significance of microcystoid macular changes in the inner nuclear layer in patients with idiopathic epiretinal membranes, with and without glaucomatous optic neuropathy.

DESIGN

Retrospective case series.

METHODS

Clinical charts and spectral-domain optical coherence tomography images of 264 eyes of 234 consecutive patients diagnosed with idiopathic epiretinal membranes were reviewed and analyzed. Surgical data were analyzed in a subgroup of eyes with microcystoid macular changes treated with pars plana vitrectomy and epiretinal and internal limiting membrane peel. In surgical cases, postoperative functional and anatomic results at 1 and 6 months were compared between glaucomatous and nonglaucomatous eyes. Associations of microcystoid macular changes with visual acuity and other morphometric parameters were assessed by means of linear or multiple logistic regressions.

RESULTS

Microcystoid macular changes in the inner nuclear layer were diagnosed in 52 out of 264 eyes with epiretinal membranes (19.7%), of which 28 (55.0%) had concomitant glaucoma. The likelihood to develop microcystoid macular changes increased at advanced glaucoma and epiretinal membrane stages. The morphology of microcystoid macular changes was similar between glaucomatous and nonglaucomatous eyes. Forty-four out of 52 eyes (84.6%) with microcystoid macular changes, of which 20 were with glaucoma and 24 without glaucoma, underwent surgery with pars plana vitrectomy and epiretinal and internal limiting membrane peel. At 1 and 6 months after surgery the mean number of microcysts decreased significantly from baseline in nonglaucomatous eyes (P = .003 and P = .002, respectively) and remained unchanged in glaucomatous eyes (P = .400 and P = .700, respectively).

CONCLUSIONS

This study reports a high frequency of microcystoid macular changes in the inner nuclear layer in eyes with concomitant epiretinal membrane and glaucomatous optic neuropathy. In glaucomatous eyes, pars plana vitrectomy with epiretinal and internal limiting membrane peel was ineffective in the treatment of microcystoid macular changes.

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.

Optical coherence tomography angiography microvascular findings in macular edema due to central and branch retinal vein occlusions

The aim of this study was to evaluate retinal and choriocapillaris vessel density using optical coherence tomography angiography (OCTA) in eyes with central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO) complicated by macular edema (ME). Sixty eyes of 60 patients with CRVO or BRVO and ME and 40 healthy subjects underwent measurements of superficial and deep foveal and parafoveal vessel density (FVD, PFVD) and choricapillary density using OCTA at baseline and 60 days after intravitreal dexamethasone implant (IVDEX). FVD and PFVD of the superficial plexus were not significantly lower in CRVO group compared to the controls while in the BRVO group overall PFVD were significantly lower compared to control group (p < 0.001). Overall PFVD of the deep plexus was significantly lower in CRVO and BRVO groups compared to the control group (p < 0.001). FVD and overall PFVD of choriocapillaris were significantly reduced compared to controls in CRVO group (p < 0.001) and PFVD of choriocapillaris was significantly reduced compared to controls in the affected hemi fields in BRVO groups (p < 0.001). OCTA showed vessel density reduction in BRVO and CRVO with main involvement of the deep retinal plexus compared to the superficial retinal plexus due to ischemia that did not recover after intravitreal dexamethasone implant.