Choroidal neovascularization

Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. This is a common symptom of the degenerative maculopathy wet AMD (age-related macular degeneration).

Causes
CNV can occur rapidly in individuals with defects in Bruch's membrane, the innermost layer of the choroid. It is also associated with excessive amounts of Vascular endothelial growth factor (VEGF). As well as in wet AMD, 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 metamorphopsia, and colour disturbances. Hemorrhaging of the new blood vessels can accelerate the onset of symptoms of CNV.

Signs
CNV can be detected by measuring the Preferential Hyperacuity Perimeter. On the basis of fluorescein angiography, CNV may be described as classic or occult.

Treatment

 * 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 injected into the eye, where it accumulates in the new blood vessels. It is then activated by a laser light. The drug destroys the new blood vessels, and prevents any new vessels forming by forming thrombi.


 * Anti-VEGF drugs, such as pegaptanib and ranibizumab, are also used to treat CNV. Anti-VEGFs bind to and inactivate Vascular endothelial growth factor.