Geographic Atrophy (GA) is a severe, advanced stage of dry Age-Related Macular Degeneration (AMD), a common condition affecting older adults. GA involves the irreversible loss of cells in the macula, the central part of the retina responsible for sharp, detailed vision. This destruction of light-sensing tissue causes a progressive and permanent loss of central vision. Because the macula is essential for tasks like reading and recognizing faces, its atrophy significantly impairs a person’s ability to perform daily activities. GA affects millions globally and is a leading cause of legal blindness.
Defining Geographic Atrophy and Its Causes
Geographic Atrophy is characterized by the death of three adjacent retinal layers: the photoreceptors, the Retinal Pigment Epithelium (RPE), and the underlying choriocapillaris. RPE cells support the photoreceptors by supplying nutrients and removing waste. When these support cells die, the overlying light-sensing photoreceptors also perish, leading to atrophy.
The disease process often begins with the accumulation of drusen, small yellow deposits of lipids and proteins beneath the retina. These deposits interfere with RPE function and lead to chronic inflammation. A biological driver of this inflammation is the overactivation of the complement system, a part of the body’s immune defense. Genetic variations in complement-related genes, such as Complement Factor H, are strongly linked to an increased risk of developing GA.
Aging is the most significant risk factor for GA, as the condition is almost exclusively seen in people over the age of 60. Beyond inherited genetic factors, modifiable lifestyle elements also contribute to the disease’s development. Smoking is a major environmental risk factor that exacerbates oxidative stress on RPE cells. A poor diet lacking in certain nutrients may also increase susceptibility to this form of advanced AMD.
Identifying Visual Symptoms and Disease Progression
The visual changes associated with GA develop slowly, often starting subtly and worsening over many years. Patients typically first notice difficulty seeing in dim or low-light conditions, which can precede significant vision loss. As the disease advances, the atrophy creates blind spots, known as scotomas, in the center of the visual field.
These scotomas make activities requiring central focus, such as reading or driving, increasingly challenging. Colors may also appear dull or washed out due to damage to the macula’s cone photoreceptors. Although GA causes severe central vision loss, peripheral vision usually remains unaffected, allowing patients to maintain mobility.
The progression of GA is slow but irreversible, with the areas of atrophy expanding outward like patches on a map. Atrophy often begins outside the fovea, the macula’s most sensitive point, but steadily progresses toward this center. Once the atrophic lesions invade the fovea, the most severe and permanent loss of central visual acuity occurs. The average growth rate of the atrophic area is approximately 2.5 millimeters squared per year.
Diagnostic Technologies Used to Identify GA
Ophthalmologists use a combination of technologies to confirm a GA diagnosis and track the expansion of atrophic lesions. Fundus Autofluorescence (FAF) imaging is the primary tool for diagnosis and monitoring. FAF detects the natural fluorescence of lipofuscin, a metabolic byproduct accumulating in RPE cells.
In areas of GA, the RPE cells are absent, resulting in a distinct, dark, or hypoautofluorescent area on the FAF image. This clearly outlines the boundaries of the atrophy, allowing clinicians to accurately measure the size and monitor the growth rate of the lesions.
Optical Coherence Tomography (OCT) is an essential non-invasive technology providing high-resolution, cross-sectional views of the retina’s layers. OCT confirms the loss of the RPE layer and overlying outer retinal tissue, visualizing the damage in depth. The characteristic finding on OCT is complete RPE and outer retinal atrophy (cRORA), which correlates directly with FAF findings.
Amsler Grid testing and standard Visual Acuity tests serve as initial screening tools. The Amsler Grid is a simple test where patients look at a grid to detect distortions or blank spots in their central vision. While helpful for detecting macular changes, the objective measurements provided by FAF and OCT are necessary for definitive diagnosis and clinical monitoring.
Current Treatment and Management Strategies
Until recently, there were no approved medical treatments to slow GA progression. However, new therapies targeting the overactive complement cascade, such as pegcetacoplan and avacincaptad pegol, have been approved. These medications are administered via injection directly into the eye to slow the rate at which atrophic lesions expand. While these treatments do not restore lost vision, their goal is to preserve remaining healthy retinal tissue.
Patients with intermediate dry AMD, the stage preceding GA, may be advised to take specific high-dose vitamin and mineral supplements. These supplements, based on the AREDS2 formulation, contain antioxidants like Vitamin C, Vitamin E, zinc, and copper. They have been shown to reduce the risk of progression to advanced AMD for certain patient groups. Adopting a healthy lifestyle, including a diet rich in leafy green vegetables and fish, is also recommended to reduce oxidative stress.
For patients experiencing vision loss, low vision rehabilitation is a fundamental part of management. Low vision specialists help patients maximize their remaining sight using adaptive devices. Tools such as powerful magnifiers, electronic readers, and contrast-enhancing devices can significantly improve quality of life. These strategies help patients maintain independence and continue performing essential daily activities.