Choroidal neovascularization (CNV) in the eye refers to the abnormal growth of new blood vessels from the choroid (the layer of blood vessels behind the retina) into the retina. This is a key feature of wet age-related macular degeneration (AMD) and other eye conditions.
Understanding CNV
- Choroid: The choroid is a layer of blood vessels that provides nourishment to the outer layers of the retina.
- Neovascularization: This term means the formation of new blood vessels. In the case of CNV, these new vessels are abnormal and fragile.
- Problem: These new vessels leak fluid and blood, which can damage the retina, leading to vision loss, distortion (metamorphopsia), and blind spots (scotomas).
CNV in the Context of AMD
CNV is most commonly associated with the "wet" or "exudative" form of age-related macular degeneration (AMD). AMD is a leading cause of vision loss in older adults.
- Dry AMD: In dry AMD, the macula (central part of the retina) thins and atrophies over time.
- Wet AMD: Wet AMD is characterized by CNV. It's less common than dry AMD, but it progresses more rapidly and causes more severe vision loss. CNV occurs when new blood vessels grow from the choroid, penetrating the Bruch's membrane and extending into the retina, leading to fluid and blood leakage.
Other Causes of CNV
Besides AMD, CNV can also be caused by:
- Myopic degeneration: High degrees of nearsightedness can stretch the retina and lead to CNV.
- Angioid streaks: Breaks in Bruch's membrane that allow CNV to develop.
- Trauma: Injury to the eye.
- Inflammatory conditions: Such as uveitis.
Diagnosis and Treatment
CNV is typically diagnosed through:
- Dilated eye exam: To visualize the retina and macula.
- Optical coherence tomography (OCT): Provides detailed images of the retina's layers.
- Fluorescein angiography (FA): A dye is injected into the bloodstream, and photographs are taken of the retina to visualize the blood vessels and any leakage.
Treatment options for CNV include:
- Anti-VEGF injections: These drugs (e.g., aflibercept, ranibizumab, bevacizumab) block vascular endothelial growth factor (VEGF), a protein that stimulates blood vessel growth. Anti-VEGF injections are the primary treatment for wet AMD and can often stabilize or improve vision.
- Photodynamic therapy (PDT): A light-sensitive drug is injected, and then a laser is used to activate the drug and damage the abnormal blood vessels.
- Laser photocoagulation: Uses a laser to directly destroy the abnormal blood vessels (less common now with the advent of anti-VEGF).
Summary
CNV is an abnormal growth of blood vessels in the eye, often associated with wet AMD, that can lead to vision loss. Early diagnosis and treatment are crucial to preserving sight.
