Geographic Atrophy (GA) is a progressive eye condition that affects the ability to see clearly. It involves the steady loss of central vision, which is necessary for tasks like reading and recognizing faces. This condition represents one of the advanced stages of vision loss related to aging. Understanding the underlying pathology is important for managing its impact on daily life.
Defining Geographic Atrophy
Geographic Atrophy is a specific, advanced form of dry Age-related Macular Degeneration (AMD). It is characterized by distinct, well-defined areas of tissue death in the retina. The term “geographic” refers to the map-like, sharply demarcated borders of these damaged regions observed during an examination.
The damage involves the irreversible breakdown of several layers of tissue in the central retina. Specifically, GA is marked by the loss of the Retinal Pigment Epithelium (RPE) cells, the overlying light-sensing photoreceptor cells, and the underlying choriocapillaris. The RPE cells are particularly important because they support the photoreceptors by supplying nutrients and removing waste.
This progressive cellular death occurs in the macula, the small central part of the retina responsible for high-resolution vision. The loss of RPE and photoreceptor cells creates a window-like defect, allowing the choroidal vessels beneath to be more visible. This tissue loss is a key pathological feature distinguishing GA from earlier stages of dry AMD. The underlying mechanism is thought to involve chronic inflammation and an overactivation of the complement system, which is a part of the body’s immune defense.
Recognizing Symptoms and Progression
The functional impact of Geographic Atrophy centers on the loss of sharp, detailed vision. Patients often first notice symptoms as difficulty with activities that require focus, such as reading small print or threading a needle. Colors may also begin to appear less vivid or washed out, and the ability to adapt to changes in light, particularly in dim environments, can be impaired.
The most characteristic symptom of advanced GA is the development of a central blind spot, known as a scotoma. This dark or blurry area corresponds directly to the regions of atrophy where the photoreceptor cells have died. While central vision is progressively lost, the peripheral or side vision usually remains unaffected, meaning the condition does not typically lead to complete blindness.
GA is generally a slow, progressive disease, but the rate of worsening can vary significantly between individuals. Areas of atrophy typically begin outside the very center of the macula, called the fovea, and slowly expand over time. When the atrophic lesions eventually grow to involve the fovea, it leads to a more severe and noticeable decline in central vision. This condition often affects both eyes, though the onset and rate of progression are frequently different for each eye.
Diagnosis and Management Options
The identification of Geographic Atrophy requires a thorough examination by an ophthalmologist, which includes a dilated eye exam to view the retina directly. However, the exact diagnosis and monitoring rely heavily on advanced imaging techniques. Optical Coherence Tomography (OCT) provides a cross-sectional view of the retina, clearly showing the loss of the RPE and photoreceptor layers.
Fundus Autofluorescence (FAF) imaging is particularly useful because it highlights the boundaries of the atrophic areas. FAF works by detecting autofluorescent molecules normally contained within healthy RPE cells, which are absent in areas of atrophy. The sharply demarcated dark areas on an FAF image allow specialists to accurately measure and track the progression of the disease.
For decades, management options were limited to low-vision aids and lifestyle adjustments, such as smoking cessation and nutritional changes. The Age-Related Eye Disease Study 2 (AREDS2) vitamins are often recommended for intermediate AMD to slow progression, but their direct effect on halting the growth of established GA lesions is less pronounced. Patients are frequently referred for vision rehabilitation to learn strategies for maximizing their remaining peripheral vision.
A recent breakthrough in treatment involves new medications that target the inflammatory complement system, which contributes to the disease process. Two FDA-approved treatments, pegcetacoplan and avacincaptad pegol, are administered as injections into the eye. Pegcetacoplan targets complement component C3, while avacincaptad pegol targets complement component C5, both aiming to modulate the overactive immune response.
These complement inhibitors do not restore vision that has already been lost, but clinical trials have demonstrated that they can slow the rate of growth of the GA lesions. Studies on these treatments showed a reduction in the mean rate of lesion growth compared to untreated eyes. This slowing of lesion expansion is intended to preserve functional vision for a longer period, offering the first pharmaceutical option to modify the course of Geographic Atrophy.