Age-related macular degeneration (AMD) is a common eye condition that can cause blurred central vision. Neovascular AMD (wet AMD) is a severe form of age-related macular degeneration that can cause rapid and significant vision loss. It is a leading cause of vision loss for older adults worldwide.
Understanding Neovascular Macular Degeneration
Neovascular macular degeneration (nAMD), or wet AMD, involves abnormal growth of fragile blood vessels beneath the macula. The macula, a central part of the retina, is responsible for sharp central vision for tasks like reading. These vessels are weak and leak fluid or blood, damaging the macula.
This leakage causes swelling and scarring, leading to distorted or blurred central vision. Unlike dry AMD, which involves macula thinning, nAMD results in more sudden and severe vision loss from leaking vessels.
The formation of these abnormal blood vessels, a process called neovascularization, is often driven by an imbalance of certain proteins, including an increase in vascular endothelial growth factor (VEGF). VEGF is a protein that promotes the growth of new blood vessels, and its increased presence can lead to the development of the leaky vessels seen in nAMD. This uncontrolled growth and leakage differentiate wet AMD and contribute to its aggressive nature.
Recognizing the Signs and Risk Factors
Individuals with nAMD may experience several symptoms. Common signs include blurred central vision, distorted straight lines (metamorphopsia), difficulty recognizing faces, or a dark spot in central vision. Reduced vision in dim lighting can also be an early indicator.
These symptoms arise because the macula is directly affected by leaking blood vessels and fluid, preventing it from properly processing light. Several factors increase the likelihood of developing nAMD, which affects people over 50.
Age is the primary risk factor, with prevalence of nAMD increasing significantly in individuals over 75. Genetic predisposition and a family history of AMD also play a role. Lifestyle factors such as smoking are also strongly associated with nAMD; current smokers may experience onset approximately five years earlier than non-smokers. Other modifiable risk factors include high blood pressure, being overweight, and a diet high in saturated fats.
Diagnostic Procedures
Ophthalmologists use several tests to diagnose and monitor nAMD. The Amsler grid, a simple grid of straight lines, is a common home monitoring tool to detect central vision changes like wavy lines or blank spots. During an office visit, a dilated eye examination allows direct viewing of the retina and macula for abnormalities.
Optical Coherence Tomography (OCT) is a non-invasive imaging technique providing high-resolution views of the retina. This scan visualizes retinal layers and detects fluid or swelling within or beneath the retina, which are hallmarks of nAMD. OCT is valuable for diagnosis and monitoring treatment effectiveness.
Fluorescein Angiography (FA) involves injecting a fluorescent dye into an arm vein. As the dye circulates through the retinal blood vessels, photographs are taken, revealing leakage from abnormal vessels under the macula. This test precisely identifies the location and extent of choroidal neovascularization, which is crucial for guiding treatment. Indocyanine Green Angiography (ICG) uses a different dye for visualizing deeper choroidal blood vessels. This can be useful when fluorescein angiography results are unclear or for certain types of nAMD.
Treatment Approaches
Treatments for nAMD focus on inhibiting the growth and leakage of abnormal blood vessels. Anti-VEGF (vascular endothelial growth factor) injections are the first-line therapy, improving outcomes for many patients. These medications block VEGF, a protein that promotes the formation of new, leaky blood vessels.
By inhibiting VEGF, these injections reduce fluid leakage, decrease swelling, and prevent further growth of abnormal vessels. The goal of anti-VEGF therapy is to stabilize vision, prevent further loss, and sometimes improve visual acuity. Treatment involves a series of intravitreal injections, delivered directly into the eye’s vitreous gel. The frequency of injections varies, often starting monthly and adjusting based on patient response.
While anti-VEGF injections are the mainstay, other therapies exist but are used less often. Photodynamic therapy (PDT) involves injecting a light-sensitive drug activated by a cold laser aimed at abnormal blood vessels, which seals off or destroys them.
Laser photocoagulation uses a hot laser to burn and seal abnormal blood vessels, but its use is limited due to the risk of creating blind spots near the macula’s center. These older treatments are less common due to the superior efficacy and safety of anti-VEGF injections.