Age-related macular degeneration (AMD) is a common eye condition and a leading cause of vision loss in adults over 50. It affects the macula, a small area within the retina responsible for sharp, detailed central vision needed for reading and recognizing faces. Damage to the macula can significantly impair a person’s ability to see objects directly in front of them, though peripheral vision typically remains unaffected.
Dry Age-Related Macular Degeneration
Dry age-related macular degeneration is the more common form of AMD, accounting for approximately 85% to 90% of all cases. This condition develops when parts of the macula thin with age, and tiny yellow deposits called drusen accumulate under the retina. Larger and more numerous drusen increase the risk of vision impairment. As drusen grow and the macula thins, the light-sensitive cells slowly break down, leading to a gradual loss of central vision. Individuals with dry AMD may experience symptoms such as blurred central vision, difficulty seeing in low light, or a need for brighter illumination when reading. In its advanced stage, known as geographic atrophy, large areas of retinal tissue can waste away, causing significant blind spots.
Wet Age-Related Macular Degeneration
Wet age-related macular degeneration is less common but more severe, responsible for about 90% of profound vision loss associated with AMD. This form occurs when abnormal, fragile blood vessels grow under the macula, a process known as choroidal neovascularization. These vessels are prone to leaking fluid or blood, which elevates the macula and causes rapid damage and scarring. This results in sudden and severe vision decline. Wet AMD often manifests with symptoms like distorted vision, where straight lines appear wavy or bent. Other common signs include dark spots, blind spots in the central visual field, or words disappearing while reading.
Key Distinctions
The fundamental difference between dry and wet AMD lies in their underlying pathological mechanisms. Dry AMD involves the slow deterioration and thinning of macular tissue, marked by the presence of drusen. In contrast, wet AMD is characterized by the abnormal growth of new, fragile blood vessels beneath the macula that leak fluid or blood, leading to significant disruption.
The rate of vision loss also distinguishes the two types. Vision loss in dry AMD is typically gradual and progresses slowly over several years. Conversely, wet AMD can cause a sudden and rapid decline in central vision due to acute leakage and bleeding. This rapid onset often necessitates urgent medical attention.
Regarding prevalence, dry AMD is far more common, affecting approximately 85% to 90% of individuals with AMD. Wet AMD is less prevalent, accounting for about 10% to 15% of cases, but it carries a higher risk of severe vision impairment. While dry AMD’s severity is generally less pronounced initially, wet AMD often results in more profound and immediate vision loss.
Symptoms also vary. Dry AMD often presents as mild blurriness, difficulty in low light, or a need for increased illumination for reading. Wet AMD, due to fluid accumulation, causes more distinct symptoms like distorted or wavy vision, blind spots, or the perception of objects changing size. These specific visual distortions are a notable indicator of wet AMD.
Diagnosis and Management
Diagnosing both types of AMD involves a comprehensive eye examination. Eye care professionals use tests such as the Amsler grid, which helps detect distorted or missing central vision. Dilated eye exams allow direct viewing of the retina and macula, identifying signs like drusen or abnormal blood vessels. Advanced imaging techniques, including Optical Coherence Tomography (OCT) and fluorescein angiography, provide detailed images and highlight leakage, particularly useful for wet AMD.
Management approaches differ by type. For dry AMD, there is currently no cure, but treatment focuses on slowing progression. This involves lifestyle adjustments, such as quitting smoking, and nutritional supplements like the AREDS (Age-Related Eye Disease Study) formula, which contains specific vitamins and minerals to reduce the risk of advanced AMD. Regular monitoring is important to detect any progression, including a potential conversion to wet AMD.
Wet AMD has more active treatment options aimed at preserving vision and preventing further damage. The most common treatment involves anti-VEGF (vascular endothelial growth factor) injections directly into the eye. These medications block a protein that stimulates the growth of new, leaky blood vessels, reducing fluid leakage and swelling. Less commonly, photodynamic therapy or laser photocoagulation may be used. Early detection and timely intervention are important for managing both forms of AMD and preserving vision.