The acronym “GA” in vision refers to Geographic Atrophy, a serious and progressive condition affecting the central part of the retina. This eye disease is an advanced form of dry Age-Related Macular Degeneration (AMD), which is a leading cause of vision loss in older adults. Geographic Atrophy results in irreversible damage to the light-sensing tissue, specifically impacting the ability to see fine details directly ahead.
Defining Geographic Atrophy
Geographic Atrophy represents the late stage of dry Age-Related Macular Degeneration, characterized by clearly defined areas of tissue death. This damage occurs in the macula, the small central area of the retina responsible for sharp, detailed central vision. The condition gets its name from the appearance of these damaged regions, which resemble distinct, map-like areas when viewed by an eye care specialist.
The physical loss of vision is caused by the irreversible breakdown of several layers of tissue in the outer retina. The initial damage involves the death of the Retinal Pigment Epithelium (RPE) cells, which are responsible for nourishing the light-sensitive photoreceptor cells. The loss of RPE cells leads to the subsequent death of the overlying photoreceptors and the underlying choriocapillaris, a layer of fine blood vessels. This cascade of cellular destruction creates patches of atrophy that expand over time.
Recognizing the Symptoms
The defining characteristic of Geographic Atrophy is a gradual, progressive loss of central vision, while the side, or peripheral, vision usually remains unaffected. This means that a person with GA may maintain their ability to navigate space but will struggle with tasks requiring high visual acuity. Symptoms may start subtly, such as needing significantly more light to read or colors appearing less vibrant and muted.
As the condition progresses, patients often experience scotomas, which are blind spots or dark patches that appear in the direct center of their field of view. These scotomas can severely hinder daily activities like reading, recognizing faces, or driving. Since the vision loss is centered, it affects the ability to focus on and resolve small details, making tasks like needlepoint or reading a clock increasingly challenging.
Risk Factors and Disease Progression
The most significant risk factor for developing Geographic Atrophy is advanced age, with the condition becoming more prevalent after the age of 60. Genetics also play a substantial part, as a family history of AMD or the presence of specific genetic variants, particularly in genes related to the body’s complement system (like C3), increases susceptibility.
Smoking is recognized as a modifiable factor that can significantly increase the risk of developing and accelerating the progression of GA. The disease is characterized by a slow but relentless expansion of the atrophic lesions, although the rate varies considerably between individuals. On average, the lesions tend to grow by about 0.28 to 0.29 millimeters per year. Lesions that are multifocal, meaning they appear in several distinct patches, often expand faster than single, unifocal lesions.
Current Status of Management
While there is no treatment that can restore the vision already lost to Geographic Atrophy, the current focus of management is on slowing the disease’s progression and maximizing remaining vision. Regular monitoring by an eye care specialist is important to track the rate of lesion expansion and to check for the possible conversion to wet AMD. Nutritional intervention involves the use of specific high-dose vitamin and mineral supplements, known as the AREDS or AREDS2 formulations, which are proven to help slow the overall progression of dry AMD.
For managing the functional impact of vision loss, low vision rehabilitation is a primary tool. This includes the use of specialized low vision aids such as high-powered magnifiers, telescopic glasses, and electronic reading devices. Two new targeted therapies, pegcetacoplan (Syfovre) and avacincaptad pegol (Izervay), have received approval for slowing the expansion of GA lesions. These treatments are administered via injection into the eye and work by targeting parts of the complement system, which is implicated in the disease process.