Active choroidal neovascularization is a serious eye condition that can significantly impair vision. It involves the growth of new, abnormal blood vessels within a specific part of the eye. This article provides a clear overview of this condition.
Understanding Active Choroidal Neovascularization
Choroidal neovascularization (CNV) refers to the development of new blood vessels originating from the choroid, the vascular layer beneath the retina. These abnormal vessels can extend into the retina, the light-sensitive tissue at the back of the eye. The term “active” signifies that these vessels are currently leaking fluid, bleeding, or causing an accumulation of fluid or blood beneath or within the retina. This ongoing activity leads to vision loss.
The macula, a small area in the center of the retina, is particularly susceptible to damage from active CNV. The macula is responsible for sharp, detailed central vision, necessary for tasks like reading, recognizing faces, and driving. When abnormal vessels leak into or beneath the macula, it directly interferes with this vision, often causing significant and rapid deterioration.
Causes and Risk Factors
Age-related macular degeneration (AMD) is the most common underlying cause of choroidal neovascularization, specifically the “wet” form of AMD. In wet AMD, the aging process can lead to changes in the eye that stimulate the growth of these unwanted vessels. These vessels are fragile and prone to leakage, causing vision problems.
Other less common causes of active choroidal neovascularization include high myopia. Certain inflammatory conditions like ocular histoplasmosis syndrome, chorioretinitis, or posterior uveitis can also lead to CNV. Additionally, angioid streaks, pseudoxanthoma elasticum, optic disc drusen, and trauma to the eye can contribute to its development. General risk factors for AMD, such as increasing age, a family history of the condition, smoking, and certain dietary patterns, may also indirectly increase the likelihood of developing CNV.
Recognizing the Symptoms
Individuals experiencing active choroidal neovascularization often notice specific changes in their vision. Blurred vision is a common early symptom, which can progress to a more pronounced haziness. Distorted vision is another strong indicator, where straight lines may appear wavy, bent, or otherwise irregular. This distortion happens because fluid or blood from the leaking vessels lifts or shifts the retinal tissue.
A central blind spot can develop, appearing as a dark or empty area directly in the center of the visual field. Objects might also appear larger or smaller than their actual size. It is important to note that active choroidal neovascularization is usually painless. Prompt medical attention is advised if any of these visual disturbances arise, as early detection can influence management outcomes. A grid pattern called the Amsler grid can be used for self-monitoring, as it helps detect subtle distortions or missing areas in central vision.
Diagnosis and Treatment Options
Diagnosing active choroidal neovascularization begins with a comprehensive eye examination by an ophthalmologist. This examination allows the doctor to assess the eye’s overall health and look for visible signs of abnormal vessel growth or fluid accumulation. Specialized imaging techniques are often necessary to confirm the diagnosis and determine the condition’s extent.
Optical Coherence Tomography (OCT) is a non-invasive imaging scan that provides high-resolution cross-sectional images of the retina. OCT can detect fluid under the retina or retinal pigment epithelium, as well as changes in retinal thickness, which are indicators of active CNV. Fluorescein Angiography (FFA) involves injecting a dye into a vein, which then travels to the eye’s blood vessels; a series of photographs are taken as the dye illuminates any leaking vessels. Indocyanine Green Angiography (ICGA) uses a different dye to visualize deeper choroidal circulation, useful in identifying CNV that might be less apparent on FFA.
The primary treatment for active choroidal neovascularization is anti-VEGF (anti-vascular endothelial growth factor) injections. VEGF is a protein that stimulates the growth of new blood vessels and increases their permeability, leading to leakage. Anti-VEGF medications, such as ranibizumab, bevacizumab, and aflibercept, work by binding to and blocking VEGF, thereby inhibiting the growth of abnormal vessels and reducing leakage. These medications are administered directly into the vitreous gel of the eye on a regular schedule determined by the ophthalmologist.
While anti-VEGF injections are the mainstay of treatment, other therapies exist but are used less frequently. Laser photocoagulation involves using a hot laser to destroy the abnormal blood vessels, but it can also damage overlying healthy retinal tissue, leading to blind spots. Photodynamic therapy (PDT) uses a light-sensitive drug activated by a cold laser to close off leaking vessels, often with less damage to surrounding tissue than traditional laser, but its effectiveness is surpassed by anti-VEGF agents. Adherence to the prescribed treatment regimen and ongoing monitoring are important for managing active CNV and preserving vision.