Type 1 choroidal neovascularization
Type 1 choroidal neovascularization
Description, Causes and Risk Factors:
Abbreviation: Type 1 CNV.
Ingrowth of new vessels from the choriocapillaris into the subretinal pigment epithelial space; associated with damage to the outer retina.
Also called occult, type 1 neovascularization refers to new blood vessels that proliferate underneath the pigment epithelium. The new capillaries originate from the choroid and form in response to damage at the pigment epithelium, the layer between the choroid and the retina. Their growth sometimes causes the pigment epithelium to detach.
Neovascularization may occur secondary to any process that damages the pigment epithelium, including age-related macular degeneration (AMD), pathological myopia, and other conditions. When new blood vessel growth occurs as a result of AMD, the condition is then called neovascular AMD. Most people with neovascular AMD have a combination of type 1 and type 2 neovascularization. When new blood vessel growth occurs without a known cause, it is called idiopathic choroidal neovascularization. Regardless of the cause of new vessel growth, it is that growth that is responsible for nearly all of the vision loss associated with these conditions.
Physicians can determine the type of neovascularization through different technologies. This is important because certain treatments can successfully destroy new blood vessel growth at some locations but not others.
Some patients presenting with type 1 neovascularization may have clinical and multimodal imaging findings more consistent with longstanding CSC (central serous chorioretinopathy) than with age-related macular degeneration. These patients are more likely to be younger, men, have thicker choroids, and have a higher prevalence of polypoidal neovasculopathy than those patients with type 1 neovascularization secondary to age-related macular degeneration. Proper identification of these patients may have implications for their natural course and management.
Signs and symptoms may include:
Paracentral or central scotoma.
Apparent change in image size.
Retinal pigment epithelial detachment.
Subretinal fibrosis (disciform scar).
Painless loss of vision.
Laboratory studies may be indicated if certain underlying medical conditions, such as pseudoxanthoma elasticum (PXE), are present.
Tests may include:
Indocyanine green angiography.
Optical coherence tomography.
Fluorescein angiography (FA).
Standard of care in Retinology today are intravitreal injections of anti-VEGF drugs to control neovascularization and reduce the area of fluid below the retinal pigment epithelium. These drugs are commonly known as Avastin and Lucentis, and although their effectiveness has been shown to significantly improve visual prognosis with choroidal neovascularization, the recurrence rate for these neovascular areas remains high. Individuals with CNV should be aware that they are at a much greater risk (25%) of developing choroidal neovascularization in fellow eye, this according to the American Academy of Ophthalmology and further supported by clinical reports.
In 'wet' (also known as 'neovascular') Age-Related Macular Degeneration, CNV is treated with photodynamic therapy coupled with a photosensitive drug such as verteporfin. The drug is given intravenously. It is then activated in the eye by a laser light. The drug destroys the new blood vessels, and prevents any new vessels forming by forming thrombi.
A modified "treat and extend" dosing regimen of intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy reduces the need for monthly visits and imaging and allows for stable long-term visual acuity in eyes with type 1 neovascularization.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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