Choroidal neovascularization (CNV) is the creation of new blood vessels in the

choroid The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye, and contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear ...

layer of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy (i.e. 'wet'

macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...

) commonly exacerbated by extreme myopia, malignant myopic degeneration, or age-related developments.

Causes

CNV can occur rapidly in individuals with defects in Bruch's membrane, the innermost layer of the

. It is also associated with excessive amounts of

vascular endothelial growth factor Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...

(VEGF). As well as in wet macular degeneration, CNV can also occur frequently with the rare genetic disease pseudoxanthoma elasticum and rarely with the more common optic disc drusen. CNV has also been associated with extreme myopia or malignant myopic degeneration, where in choroidal neovascularization occurs primarily in the presence of cracks within the retinal (specifically) macular tissue known as lacquer cracks.

Symptoms

CNV can create a sudden deterioration of central vision, noticeable within a few weeks. Other symptoms which can occur include color disturbances, and

metamorphopsia Metamorphopsia (from , ) is a type of distorted vision in which a grid of straight lines appears wavy and parts of the grid may appear blank. People can first notice they suffer with the condition when looking at mini-blinds in their home. For examp ...

(distortions in which straight lines appear wavy). Hemorrhaging of the new blood vessels can accelerate the onset of symptoms of CNV. CNV may also include the feeling of pressure behind your eye. Using modern

optical coherence tomography Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media (e.g., biological tissue). It is used for medic ...

devices, it is possible to detect non-exudative neovascular membranes, that are typically asymptomatic.

Identification

CNV can be detected by using a type of

perimetry A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits. ...

called preferential hyperacuity perimetry. On the basis of fluorescein angiography, CNV may be described as classic or occult. Two other tests that help identify the condition include indocyanine green angiography and

Treatment

CNV is conventionally treated with intravitreal injections of angiogenesis inhibitors (also known as "anti-VEGF" drugs) to control neovascularization and reduce the area of fluid below the retinal pigment epithelium. Angiogenesis inhibitors include

pegaptanib Pegaptanib sodium injection (brand name Macugen) is an anti-angiogenic medicine for the treatment of neovascular (wet) age-related macular degeneration (AMD). It was discovered by NeXstar Pharmaceuticals (which merged with Gilead Sciences in 199 ...

, ranibizumab and

bevacizumab Bevacizumab, sold under the brand name Avastin among others, is a medication used to treat a number of types of cancers and a specific eye disease. For cancer, it is given by slow injection into a vein ( intravenous) and used for colon cancer, ...

(known by a variety of trade names, such as Macugen, Avastin or Lucentis). These inhibitors slow or stop the formation of new blood vessels ( angiogenesis), typically by binding to or deactivating the transmission of

('VEGF'), a signal protein produced by cells to stimulate formation of new blood vessels. The effectiveness of angiogenesis inhibitors has been shown to significantly improve visual prognosis with CNV, the recurrence rate for these neovascular areas remains high. CNV may also be treated with photodynamic therapy (PDT) coupled with a photosensitive drug such as

verteporfin Verteporfin (trade name Visudyne), a benzoporphyrin derivative, is a medication used as a photosensitizer for photodynamic therapy to eliminate the abnormal blood vessels in the eye associated with conditions such as the wet form of macular degen ...

(Visudyne). The drug is given

intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

. 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 Cochrane Review published in 2016 found that people with severe myopia (short-sightedness or near-sightedness) may benefit from being given anti-VEGF treatment.

References

{{Ocular vascular disorder agents Ophthalmology

Causes

Symptoms

Identification

Treatment

See also

References