Choroidal neovascularization (CNV) refers to the growth of new blood vessels from the choroid, through breaks in Bruch’s membrane, either under the retinal pigment epithelium (RPE, type 1) or the sensory retina (type 2) or both. The condition has potentially devastating visual consequences. The etiology of CNV appears to be related to damage to the RPE and Bruch’s membrane, in the presence of retinal hypoxia. The RPE serves as a key part of the blood-retinal barrier, and a breach may allow angiogenic factors to act on the choroidal vasculature.
- Degenerative conditions – age-related macular degeneration, myopia, angioid streaks; among the more common conditions associated with CNV
- Inflammatory or infectious conditions – sarcoidosis, histoplasmosis, acute posterior multifocal placoid pigment epitheliopathy, birdshot chorioretinitis, serpiginous choroiditis, toxoplasmosis
- Tumors – choroidal nevi, melanoma, osteoma, combined hamartoma Trauma – choroidal rupture, laser photocoagulation
- hlereditary/congenital – Best’s vitelliform dystrophy, Coats disease (retinal telangiectasis), coloboma, pattern dystrophies, dominant drusen, optic nerve pit
Possible symptoms include distortion of straight lines or edges, sudden visual loss or the development of a noticeable blind spot in the visual field.
Choroidal neovascularization may be difficult to see ophthalmoscopically in the early stages of development. Typically it may be first seen as a grey-green subretinal lesion, and there may be associated hemorrhage, lipid exudation or fluid. Fluorescein angiography enables the CNV to be better characterized:
(a) Subfoval if the CNV extends under the centre of the fovea; (b) Juxtafoval if the CNV extends to within 1 to 199 microns from the centre of the fovea, and (c) Extrafoveal if the CNV is 200 microns or more from the foveal centre.
• Classic versus occult:
- – classic CNV shows a welldemarcated hyperfluorescence in the early phase of the angiogram
- – occult CNV has poorly defined boundaries with late progressive hyperfluorescence
- – combination.
A very common (greater than 1/10) to common (approximately 1/100) complication of many ocular diseases.
Sight threatening; requires prompt investigation and treatment.
See list of associated conditions above.
Currently available therapies for CNV aim to reduce the risk of progression and complications. For more detail, see Agerelated macular degeneration (AMD) – dry: management and AMD – exudative: management.
Choroidal neovascularization with associated hemorrhages. For further figures, see Agerelated macular degeneration – exudative and Macular edema.
Additional tests Fluorescein angiography is used to diagnose CNV and to direct treatment, as discussed above. Indocyanine green (ICG) angiography may further assist assessment.
Laser treatment Argon laser treatment is mainly used for extrafoveal CNV, to avoid affecting vision. Verteporfin photodynamic treatment (PDT) is most often used for subfoveal, predominantly classic CNV.
Injection CNV may be treated with repeated doses of anti-angiogenic drugs: Anecortave acetate is delivered by peri-ocular injection, and Pegaptanib sodium (Macugen, Eyetech) and ranibizumab (Lucentis, Genentech and Novartis) are anti- vascular endothelial growth factor (anti-VEGF) drugs delivered by an intravitreal injection
Oral medication and diet The risk of development of CNV in AMD is reduced with vitamin supplementation, daily fruit consumption and cessation of smoking. The patient’s general vascular status should be reviewed in relation to systemic conditions.
Review Patients at risk of CNV may be reviewed annually, but encouraged to attend immediately if signs of reduced vision or distortion are noted. They may be provided with an Amsler (grid) chart for home use to self-assess the vision in each eye for distortion.
Refractive correction or low vision aids If bilateral low vision results, then low vision aids may be required such as high reading addition power, telescopes, hand magnifiers and closed circuit TV magnification systems.