Geographic Atrophy (GA) is a severe, progressive eye condition resulting in the irreversible loss of central vision. It affects the macula, the highly sensitive area at the center of the retina responsible for detailed, straight-ahead sight. This disorder impacts a person’s ability to perform daily activities requiring sharp focus, such as reading, driving, and recognizing faces. The condition is characterized by the gradual degeneration of retinal tissue, which leads to a permanent blind spot in the center of the visual field.
Defining Geographic Atrophy
Geographic Atrophy (GA) is the advanced, late-stage form of dry Age-Related Macular Degeneration (AMD). This progression is marked by the death of two cell layers in the macula: the retinal pigment epithelium (RPE) and the overlying photoreceptors. The RPE layer supplies nutrients to and removes waste from the light-sensing photoreceptor cells. When RPE cells die, the photoreceptors they support also perish, leading to patches of non-functional tissue.
The term “geographic” is used because these areas of dead cells appear as distinct, map-like regions of atrophy when examined by an ophthalmologist. This cellular loss is irreversible and progressive, meaning the patches of damage slowly expand over time. This breakdown is linked to an overactive inflammatory response in the eye, primarily involving the complement cascade of the immune system. This inflammatory process accelerates the degradation of the RPE and photoreceptors.
Prevalence and Classification
Geographic Atrophy is not considered a rare disease; it is a common cause of irreversible vision loss in developed nations. The legal definition of a rare disease in the United States is a condition affecting fewer than 200,000 people, established under the Orphan Drug Act. The European Union defines a rare disease as one affecting less than five out of every 10,000 people. GA far exceeds these official thresholds.
Globally, GA affects more than 5 million people, including approximately 1 million people in the United States alone. The condition affects about 20% of all individuals who have Age-Related Macular Degeneration. The number of people affected is expected to rise significantly as the global population ages. This high prevalence confirms GA is a major public health concern.
Visual Impact and Progression
The most common symptom is a gradual loss of sharp, central vision, often manifesting initially as difficulty reading fine print or seeing in dim light. As the disease advances, cell death creates scotomas, which are fixed blind spots appearing in or near the center of the visual field. These blind spots make activities like recognizing faces or following a line of text challenging.
The progression of GA is typically slow but relentless, with the patches of atrophy expanding over time. The atrophic lesions often begin surrounding the fovea, the very center of the macula responsible for the sharpest vision. As the lesions expand and coalesce, they eventually damage the fovea. This damage leads to a rapid and severe decline in central visual acuity, and the rate of vision loss correlates directly with the lesion size and foveal involvement.
Current Management Strategies
Monitoring and Supplements
For many years, GA management was limited to monitoring and lifestyle adjustments. These adjustments included recommending specific high-dose antioxidant and mineral supplements, such as the Age-Related Eye Disease Study (AREDS) formula. AREDS can slow the progression of earlier-stage dry AMD. Regular monitoring by an ophthalmologist using advanced imaging, such as optical coherence tomography and fundus autofluorescence, remains a component of care.
Complement Inhibitor Therapies
The landscape of GA treatment shifted with the recent approval of the first pharmaceutical therapies designed to slow the disease’s progression. These new treatments are complement inhibitors, such as pegcetacoplan (Syfovre) and avacincaptad pegol (Izervay), administered via intravitreal injection. These drugs target and inhibit specific proteins in the complement cascade, a part of the immune system contributing to inflammation and cell death in the macula.
Pegcetacoplan targets the C3 protein, while avacincaptad pegol inhibits the C5 protein, both acting to reduce the overactive immune response. Clinical trials demonstrated that these therapies can slow the annual growth rate of the atrophic lesions. These treatments are designed to preserve vision by slowing progression, but they cannot restore vision already lost due to existing atrophy.