Retinal Neovascularization (retinal + neovascularization)

Distribution by Scientific Domains

Selected Abstracts

Vascular endothelial growth factor and diabetic retinopathy: pathophysiological mechanisms and treatment perspectives

Ruth B. Caldwell
Abstract Retinal neovascularization and macular edema are central features of diabetic retinopathy, the major cause of blindness in the developed world. Current treatments are limited in their efficacy and are associated with significant adverse effects. Characterization of the molecular and cellular processes involved in vascular growth and permeability has led to the recognition that the angiogenic growth factor and vascular permeability factor vascular endothelial growth factor (VEGF) plays a pivotal role in the retinal microvascular complications of diabetes. Therefore, VEGF represents an exciting target for therapeutic intervention in diabetic retinopathy. This review highlights the current understanding of the mechanisms that regulate VEGF gene expression and mediate its biological effects and how these processes may become altered during diabetes. The cellular and molecular alterations that characterize experimental models of diabetes are considered in relation to the influence of high glucose-mediated oxidative stress on VEGF expression and on the mechanisms of VEGF's actions under hyperglycemic induction. Finally, potential therapeutic strategies for preventing VEGF overexpression or blocking its pathological effects in the diabetic retina are considered. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Therapeutic efficacy of intravitreal bevacizumab on posterior uveitis complicated by neovascularization

Shree Kurup
Abstract. Purpose:, To evaluate the therapeutic effect of intravitreal bevacizumab in patients with uveitis-associated choroidal/retinal neovascularization. Methods:, Two female patients (40 years, 15 years) with posterior uveitis, (one presumed ocular sarcoidosis, one lupus) were evaluated for neovascularization of the posterior segment. Both patients were given a single dose of 1.25 mg intravitreal bevacizumab. Results:, Significant anatomical and functional recovery was evident in both patients within a few weeks. Conclusion:, In selected uveitic patients, bevacizumab may be an option for managing neovascularization. [source]

Pigment epithelium-derived factor induces the production of chemokines by rat microglia

GLIA, Issue 4 2005
Asako Takanohashi
Abstract Many studies have shown that pigment epithelium-derived factor (PEDF) has neurotrophic effects on retinal cells and hippocampal, spinal cord, and cerebellar granule cell neurons, but much less work has examined the effects of PEDF on glia. In this study, we show that PEDF changes microglial morphology within 1 h of exposure, to a more deactivated form, while having no effect on the expression of such activation markers as OX-42 and ED-1. In contrast, urea activates acid phosphatase, and PEDF blocks that activation. PEDF also activates NF,B, accompanied by the induction of mRNAs and proteins for the chemokines macrophage inflammatory protein-1, (MIP-1,, MIP-2, and MIP-3,. All the chemokines stimulate acid phosphatase activity, and high doses of MIP-2 and MIP-3,), alter the morphology of the microglia at 1 h after treatment. These results suggest that the use of PEDF for clinical treatments, such as for retinal neovascularization, brain injury, or ischemia, should be undertaken with caution because of the possibility of induction of inflammation caused by microglial or other immune cell migration in response to the chemokines induced by PEDF. © 2005 Wiley-Liss, Inc. [source]

Pigment epithelium-derived factor inhibits retinal and choroidal neovascularization

Keisuke Mori
In this study, we investigated whether overexpression of pigment epithelium-derived factor (PEDF) by gene transfer can inhibit neovascularization by testing its effect in three different models of ocular neovascularization. Intravitreous injection of an adenoviral vector encoding PEDF resulted in expression of PEDF mRNA in the eye measured by RT-PCR and increased immunohistochemical staining for PEDF protein throughout the retina. In mice with laser-induced rupture of Bruch's membrane, choroidal neovascularization was significantly reduced after intravitreous injection of PEDF vector compared to injection of null vector or no injection. Subretinal injection of the PEDF vector resulted in prominent staining for PEDF in retinal pigmented epithelial cells and strong inhibition of choroidal neovascularization. In two models of retinal neovascularization (transgenic mice with increased expression of vascular endothelial growth factor (VEGF) in photoreceptors and mice with oxygen-induced ischemic retinopathy), intravitreous injection of null vector resulted in decreased neovascularization compared to no injection, but intravitreous injection of PEDF vector resulted in further inhibition of neovascularization that was statistically significant. These data suggest that sustained increased intraocular expression of PEDF by gene therapy might provide a promising approach for treatment of ocular neovascularization. © 2001 Wiley-Liss, Inc. [source]

2414: Laser and vitrectomy

Purpose Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Methods Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Results Retinal photocoagulation has also repeatedly been shown to improve retinal oxygenation. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids Conclusion Vitrectomy and laser retinal treatment both improve oxygenation of the ischemic retina, reduce VEGF formation and thereby reduce neovascularisation and edema. [source]

Risk of retinal neovascularization in the second eye in patients with proliferative diabetic retinopathy

Edda Vésteinsdóttir
Abstract. Purpose:, This study aimed to evaluate the risk of proliferative diabetic retinopathy (DR) in the fellow eye of an eye with existing proliferative DR. Methods:, Our DR screening programme database listed 1513 diabetes patients alive at the time of the study. Seventy-six had proliferative DR in one or both eyes. Results:, In 28 of the 76 (37%) diabetes patients, proliferative DR was diagnosed in both eyes at the same examination. Another 28 patients developed proliferative DR in the second eye within 5 years of its diagnosis in the first eye, bringing the total number of diabetes patients with proliferative DR in both eyes at 5 years to 56 (74%). Almost all the diabetes patients eventually developed proliferative DR in the second eye. The median duration of diabetes before the development of proliferative retinopathy was 19 years for type 1 and 14 years for type 2 diabetes. Conclusions:, Proliferative DR is a bilateral disease. Diabetes patients with proliferative DR in one eye are at high risk of developing neovascularization in the second eye and close follow-up is recommended. [source]

The therapeutic effects of retinal laser treatment and vitrectomy.

A theory based on oxygen, vascular physiology
ABSTRACT. The physiologic mechanism of photocoagulation can been seen in the following steps. The physical light energy is absorbed in the melanin of the retinal pigment epithelium. The adjacent photoreceptors are destroyed and are replaced by a glial scar and the oxygen consumption of the outer retina is reduced. Oxygen that normally diffuses from the choriocapillaris into the retina can now diffuse through the laser scars in the photoreceptor layer without being consumed in the mitochondria of the photoreceptors. This oxygen flux reaches the inner retina to relieve inner retinal hypoxia and raise the oxygen tension. As a result, the retinal arteries constrict and the bloodflow decreases. Hypoxia relief reduces production of growth factors such as VEGF and neovascularization is reduced or stopped. Vasoconstriction increases arteriolar resistance, decreases hydrostatic pressure in capillaries and venules and reduces edema formation according to Starling's law. Vitrectomy also improves retinal oxygenation by allowing oxygen and other nutrients to be transported in water currents in the vitreous cavity from well oxygenated to ischemic areas of the retina. Vitrectomy and retinal photocoagulation both improve retinal oxygenation and both reduce diabetic macular edema and retinal neovascularization. [source]

Retinitis pigmentosa associated with peripheral sea fan neovascularization

Sibel Kaday
ABSTRACT. Purpose: To describe a case with retinitis pigmentosa associated with sea fan type retinal neovascularization. Methods: Complete ocular examination including fluorescein angiography was performed in a 9-year-old girl. Results: Ophthalmoscopically, in addition to arteriolar narrowing and bone corpuscular pigmentation of both retinae, a vascular lesion with surrounding intraretinal exudation was noted in the upper equatorial region of the right eye. On fluorescein angiography, the lesion stained in the form of a sea fan neovascularization. Conclusion: Sea fan type of neovascularization can be seen in association with retinitis pigmentosa. Fluorescein angiography is important in identifying the exact nature of such a lesion. [source]

Treatments for choroidal and retinal neovascularization: a focus on oligonucleotide therapy and delivery for the regulation of gene function

Robert J Marano PhD
Abstract Blinding eye diseases caused by neovascularization of the retinal tissue are the leading cause of blindness in Western societies. Current treatments, such as laser photocoagulation, are limited in their effectiveness at halting the progression of angiogenesis and are unable to reduce the number of vessels once they have developed. In addition, although complete blindness is often avoided, vision is often permanently impaired by the treatment itself. Several less invasive treatments are being developed and one of these is oligonucleotide gene therapy in which short stretches of nucleotides are being used as inhibitors of key, metabolic processes involved in angiogenesis. Combined with this is the development of new and improved nucleotide chemistries aimed at overcoming many of the problems associated with oligonucleotide gene therapy, such as poor longevity because of endonuclease activity. In addition, advancements in delivery systems have further enhanced the efficacy of oligonucleotide gene therapy by increasing cellular penetration and localizing delivery to specific cell types and organs. [source]