Age-related Macular Degeneration (AMD) is a progressive eye condition targeting the macula, the central part of the retina responsible for sharp, straight-ahead vision. AMD is the leading cause of irreversible vision impairment in older adults. While most cases begin as the less aggressive “dry” form, about one in ten people progress to the more severe neovascular, or “wet,” AMD. Neovascular AMD is characterized by Choroidal Neovascularization (CNV), where abnormal blood vessels grow and cause damage. The stage known as “active CNV” is rapidly progressive and demands immediate attention, though modern therapies can stabilize or improve vision.
Understanding Neovascular AMD and CNV
Neovascular AMD is characterized by Choroidal Neovascularization (CNV), the abnormal proliferation of new, fragile blood vessels. These vessels originate from the choroid, the layer beneath the retina, and grow into the retinal tissue. This growth is driven by an overproduction of Vascular Endothelial Growth Factor (VEGF), a protein that signals the body to create new blood vessels.
Unlike healthy vessels, CNV structures are weak and leaky, allowing fluid and blood to escape beneath and within the retina. This leakage distorts vision by elevating the retinal surface. Over time, this accumulation damages photoreceptors and can lead to permanent scar tissue, resulting in irreversible central vision loss. Active CNV, marked by leakage and fluid buildup, requires timely intervention to stop this destructive process.
Recognizing the Signs and Symptoms
The onset of active CNV often presents as a sudden change in central vision, requiring urgent medical consultation. The most common symptom is metamorphopsia, where straight lines appear wavy, bent, or distorted. This warping occurs because leaking fluid physically distorts the macula’s surface.
Patients may also notice a scotoma, an area of missing or blank vision appearing as a dark or gray spot in the center of their sight. This central blind spot makes tasks like reading or recognizing faces difficult. Other changes include rapid blurring or dimming of central vision and sometimes an alteration in color perception.
Diagnostic Procedures
Ophthalmologists use advanced imaging technologies to confirm CNV presence and activity. Optical Coherence Tomography (OCT) is the primary diagnostic tool, non-invasively visualizing retinal layers. The OCT scan creates cross-sectional images that reveal the presence and location of fluid, such as subretinal fluid (SRF) and intraretinal fluid (IRF), which indicate active disease.
Fluorescein Angiography (FA) is a standard test involving the injection of a fluorescent dye into the arm vein. As the dye circulates, a rapid sequence of photographs maps the circulation. FA highlights the CNV complex by showing where the dye leaks from abnormal vessels, providing direct evidence of active leakage. Indocyanine Green Angiography (ICG) uses a different dye, helpful for visualizing the choroidal circulation and CNV that lies deeper beneath the retina.
Primary Treatment Strategies
The most effective approach for treating active CNV is Anti-Vascular Endothelial Growth Factor (Anti-VEGF) therapy. This treatment targets the underlying mechanism by blocking the VEGF protein. Neutralizing VEGF inhibits new blood vessel formation and reduces leakage and fluid accumulation from existing CNV.
Anti-VEGF medications (e.g., ranibizumab, aflibercept, and bevacizumab) are administered directly into the eye via a sterile intravitreal injection. The procedure is fast and uses anesthetic to minimize discomfort. The goal is to resolve the fluid and prevent further macular damage.
Treatment begins with a “loading phase,” typically monthly injections for the first three months, to achieve rapid disease control. Afterward, the physician determines a long-term dosing regimen to maintain visual gains and prevent recurrence. Two common maintenance strategies are the “Treat and Extend” (T&E) and “Pro Re Nata” (PRN) regimens.
Maintenance Regimens
The T&E protocol involves gradually increasing the interval between injections as long as the CNV remains inactive, maximizing time between treatments without losing efficacy. The PRN, or “as needed,” approach requires frequent monitoring visits, and treatment is only given if signs of CNV activity, such as new fluid on OCT, reappear. The T&E approach is often favored because it results in better long-term visual outcomes by ensuring continuous disease suppression. Older treatments, such as Photodynamic Therapy (PDT) or thermal laser, are typically reserved for specific situations or cases that do not respond well to Anti-VEGF medications.
Long-Term Monitoring and Lifestyle Adjustments
Neovascular AMD is a chronic condition, and recurrence of CNV activity is common even after successful treatment. Continuous monitoring is necessary to catch any returning signs of fluid or leakage early. Patients are instructed to use an Amsler grid at home for daily self-monitoring.
The Amsler grid is a square chart with a central dot and straight lines. By checking each eye separately, patients can detect new symptoms like wavy lines or the sudden appearance of blurry or dark spots. Any change on the grid should prompt an immediate call to the ophthalmologist, as early detection allows for prompt re-initiation of treatment.
Lifestyle choices also support eye health and manage AMD progression, particularly in the unaffected eye. This includes a diet rich in antioxidants, lutein, and zeaxanthin, found in leafy green vegetables. Smoking cessation is strongly recommended, as smoking is a significant risk factor for AMD development and progression. Specific nutritional supplements, often referred to as AREDS formulations, may also be recommended to slow disease progression.