Regulators of vascular permeability: potential sites for intervention in the treatment of macular edema

Radiation retinopathy intricacies and advances in management

Background: Radiation retinopathy is a chronic, progressive, vision-threatening complication from exposure to various radiation sources. While several treatment modalities are available, proper management for this disease is a continuing challenge with no consensus on the most efficacious.Objective: The aim of this article is to provide an updated review of the published literature on the course of the disease, available treatments and their efficacies, frequency of regimen, core issues in patient management, and additional newer treatment modalities, including possible prophylactic approaches.Value: We also highlighted the challenges encountered with managing chronically treated patients through an analysis of a clinical case report on a patient who was treated for several years with different modalities after a diagnosis of radiation retinopathy.

Radiation Retinopathy: Detection and Management Strategies

A gradual shift in trend from primary enucleation to globe salvaging radiation therapy for the management of ocular tumors has resulted in the rise of several post-treatment ocular complications including radiation retinopathy. Radiation retinopathy is a chronic, progressive, and occlusive vasculopathy that can manifest anytime between 1 month to 15 years after starting radiation therapy. The aim of treatment in most of these cases is to prevent further vision loss. Treatment options such as laser photocoagulation, anti-vascular endothelial growth factor and intraviral steroids have been described. However, despite several advances in diagnostic and therapeutic modalities, a significant proportion of eyes with radiation retinopathy eventually go blind. This review summarises some of the clinical features, investigative modalities, and recent therapeutic strategies used in the management of radiation retinopathy.

Intravitreal triamcinolone acetate for radiation maculopathy recalcitrant to high-dose intravitreal bevacizumab

BACKGROUND/AIMS

To evaluate the effect of adjuvant intravitreal triamcinolone acetonide (ITA) for radiation maculopathy (RM) recalcitrant to high-dose bevacizumab in patients with choroidal melanoma after plaque radiotherapy.

METHODS

Eight eyes of eight patients with RM secondary to plaque radiotherapy for choroidal melanoma, recalcitrant to high-dose bevacizumab (3.0 mg) were retrospectively evaluated. Intravitreal injections of ITA (4 mg/0.1 mL) were performed at 4-week to 16-week intervals as an adjunct to continued bevacizumab therapy. Change in central foveal thickness (CFT) as measured by optical coherence tomography and change in visual acuity (VA) were the main outcome measures.

RESULTS

At the time of diagnosis of choroidal melanoma, VA was 20/20 to 20/50 in 88% (n=7) and 20/60 to 20/200 in 12% (n=1). The mean radiation dose to the fovea was 81 Gy (median 75.2 Gy; range: 22.72-132.8 Gy). The mean onset to RM was 25 months after plaque therapy (median 25 months; range 12-44 months). At the time of initiation of ITA, VA was 20/20 to 20/50 in 38% (3/8), and 20/60 to 20/200 in 62% (5/8). After initiation of ITA, VA was stable or improved in 100% of patients (n=8) at 3 months, 88% at 6 months, 88% at 9 months and 75% at 12 months. Mean CFT was 417 µm at ITA initiation, 339 µm at 1 month, 355 µm at 6 months, 339 µm at 9 months and 359 µm at 1 year.

CONCLUSION

Intravitreal triamcinolone can be added to preserve vision and decrease macular oedema in patients with RM recalcitrant to high-dose anti-vascular endothelial growth factor agents.

Therapeutic potential of a monoclonal antibody blocking the Wnt pathway in diabetic retinopathy

Dysregulation of Wnt/β-catenin signaling contributes to the development of diabetic retinopathy by inducing retinal inflammation, vascular leakage, and neovascularization. Here, we evaluated the inhibitory effect of a monoclonal antibody (Mab) specific for the E1E2 domain of Wnt coreceptor low-density lipoprotein receptor-related protein 6, Mab2F1, on canonical Wnt signaling and its therapeutic potential for diabetic retinopathy. Mab2F1 displayed robust inhibition on Wnt signaling with a half-maximal inhibitory concentration (IC₅₀) of 20 μg/mL in retinal pigment epithelial cells. In addition, Mab2F1 also attenuated the accumulation of β-catenin and overexpression of vascular endothelial growth factor, intercellular adhesion molecule-1, and tumor necrosis factor-α induced by high-glucose medium in retinal endothelial cells. In vivo, an intravitreal injection of Mab2F1 significantly reduced retinal vascular leakage and decreased preretinal vascular cells in oxygen-induced retinopathy (OIR) rats, demonstrating its inhibitory effects on ischemia-induced retinal neovascularization. Moreover, Mab2F1 blocked the overexpression of the inflammatory/angiogenic factors, attenuated leukostasis, and reduced retinal vascular leakage in both early and late stages of streptozotocin-induced diabetes. In conclusion, Mab2F1 inhibits canonical Wnt signaling, vascular leakage, and inflammation in the retina of diabetic retinopathy models, suggesting its potential to be used as a therapeutic agent in combination with other antiangiogenic compounds.

Pigment epithelium-derived factor maintains retinal pigment epithelium function by inhibiting vascular endothelial growth factor-R2 signaling through gamma-secretase

Wet age-related macular degeneration (AMD) attacks the integrity of the retinal pigment epithelium (RPE) barrier system. The pathogenic process was hypothesized to be mediated by vascular endothelial growth factor (VEGF) and antagonized by pigment epithelium-derived factor (PEDF). To dissect these functional interactions, monolayer cultures of RPE cells were established, and changes in transepithelial resistance were evaluated after administration of PEDF, placenta growth factor (VEGF-R1 agonist), and VEGF-E (VEGF-R2 agonist). A recently described mechanism of VEGF inhibition in endothelia required the release of VEGF-R1 intracellular domain by gamma-secretase. To evaluate this pathway in the RPE, cells were pretreated with inhibitors DAPT or LY411575. Processing of VEGF receptors was assessed by Western blot analysis. Administration of VEGF-E rapidly increased RPE permeability, and PEDF inhibited the VEGF-E response dose-dependently. Both gamma-secretase antagonists prevented the inhibitory effects of PEDF. The co-administration of PEDF and VEGF-E depleted the amount of VEGF-R2 in the membrane and increased the amount of VEGF-R2 ectodomain in the media. Therefore, the inhibitory effect of PEDF appears to be mediated via the processing of VEGF-R2 by gamma-secretase. gamma-Secretase generates the amyloid-beta (Abeta) peptide of Alzheimer disease from its precursor (amyloid precursor protein). This peptide is also a component of drusen in dry AMD. The results support the hypothesis that misregulation of gamma-secretase may not only lead to Abeta deposits in dry AMD but can also be damaging to RPE function by blocking the protective effects of PEDF to prevent VEGF from driving the dry to wet AMD transition.

Multiple repeated intravitreal triamcinolone treatments for radiation-induced macular edema

BACKGROUND AND PURPOSE

This report discusses a patient with a predictably and repetitively favorable anatomic and functional response to intravitreal triamcinolone for radiation-induced macular edema. The purpose of this report is to demonstrate a situation where this treatment may have a favorable outcome over time.

METHOD

Retrospective interventional case study.

RESULT

Restoration of normal macular contour as well as maintenance of good vision after several treatments with intravitreal triamcinolone.

CONCLUSION

Intravitreal triamcinolone is a well-established treatment for macular edema. In the vast majority of cases, its effect is transient, and additional treatments are necessary. It is important to realize that, in certain cases which are effectively treated with this modality, it may allow for preservation of good vision over time. One must be vigilant for the known complications of intravitreal triamcinolone, especially increased intraocular pressure and cataract progression.

Vitreous fluid biomarkers

Interactions between cells and the network of secreted proteins are associated with the ocular disease. In most cases, clinical appearcance is sufficiently diagnostic. However, in cases of nonspecific or atypical clinical presentation, diagnostic sampling of vitreous fluid can aid diagnosis and treatment for ocular disease. Progresses in the basic sciences, particularly molecular biology, and advances in surgical instrumentation have greatly enhanced the diagnostic armamentarium. These developments also have led to a better understanding of the pathophysiological processes involved in ocular diseases and have prompted evolution of new therapeutic modalities. In this chapter, we review techniques for vitreous fluid sampling and biomarker quantitation thereof. The molecular biology of bioactive vitreous fluid factors is also discussed with respect to their clinical involvement in the development of ocular disease.

Zystoides Makulaödem bei Uveitis

Cystoid macular edema (CME) is the most frequent cause of visual deterioration in uveitis patients. Intraocular inflammation disturbs the blood-retina barrier and leads to retinal edema. The basis of successful treatment is the anti-inflammatory and immunosuppressive therapy of uveitis. Restoration of the blood-retina barrier is mediated by corticosteroids and nonsteroidal anti-inflammatory agents. Resorption of extracellular fluid is improved by systemic carboanhydrase inhibitors. Despite aggressive therapy loss of visual acuity is frequent. Therefore, early diagnosis of CME and initiation of treatment, even if visual acuity is not yet impeded, is mandatory.