Geographic atrophy (GA), also known as atrophic age-related macular degeneration (AMD) or advanced dry AMD, is an advanced form of age-related macular degeneration that can result in the progressive and irreversible loss of retinal tissue (photoreceptors, retinal pigment epithelium, choriocapillaris) which can lead to a loss of central vision over time. [1] [2] [3] [4] It is estimated that GA affects over 5 million people worldwide and approximately 1 million patients in the US, [5] [6] which is similar to the prevalence of neovascular (wet) AMD, the other advanced form of the disease.
The incidence of advanced AMD, both geographic atrophy and neovascular AMD, increases exponentially with age. The aim of most current clinical trials is to reduce the progression of GA lesion enlargement. [7]
Geographic atrophy is a chronic disease, which leads to visual function loss. This often results in difficulties performing daily tasks such as reading, recognizing faces, and driving, and ultimately has severe consequences on independence. [8] [9] [10]
Initially, patients often have good visual acuity if the GA lesions are not involved in the central macular, or fovea, region of the retina. [7] [11] As such, a standard vision test may underrepresent the visual deficit experienced by patients who report challenges reading, driving or seeing in low light conditions. [12] Reading speed is often initially unaffected due to foveal sparing, but worsens progressively as the area of atrophy enlarges. [13] [14] [15] As the disease progresses, vision-related quality-of-life declines markedly. [16]
While fluorescein angiography and optical coherence tomography are today well established for diagnosing and tracking progression in geographic atrophy more complex diagnostic assessments may be required in the context of clinical trials. [17] In February 2023, the FDA approved Pegcetacoplan for the treatment of people with geographic atrophy secondary to age-related macular degeneration. [18]
The pathogenesis of GA is not fully understood yet. It is likely multifactorial and triggered by intrinsic and extrinsic stressors of the poorly regenerative retinal pigment epithelium (RPE), particularly oxidative stress caused by the high metabolic demand of photoreceptors, photo-oxidation, and environmental stressors such as cigarette smoke. Variations in several genes, particularly in the complement system, increase the risk of developing GA. This is an active area of research but the current hypothesis is that with aging, damage caused by these stressors accumulates, which coupled with a genetic predisposition, results in the appearance of drusen and lipofuscin deposits (early and intermediate AMD). These and other products of oxidative stress can trigger inflammation via multiple pathways, particularly the complement cascade, ultimately leading to loss of photoreceptors, RPE, and choriocapillaris, culminating in atrophic lesions that grow over time. [19] [20]
Age-related macular degeneration (AMD) is characterized by retinal iron accumulation and lipid peroxidation. Ferroptosis is initiated by lipid peroxidation and is characterized by iron-dependent accumulation. Studies on iron accumulation and elevated lipid peroxidation in the aging retina, and their intimate role in ferroptosis, have implicated ferroptosis in AMD pathogenesis. [21]
A plethora of in vivo risk factors for GA progression have been published and validated. [22]
Recent studies indicate that geographic atrophy may be due to deficiencies in blood flow within the choriocapillaris. [23] [24] [25] These studies used swept-source optical coherence tomography angiography to examine the choriocapillaris. Using imaging algorithms, they then determined which regions of the choriocapillaris had deficient blood flow, thus creating a heat map of the blood supply to the retinal pigment epithelium. They went on to use fundus autofluorescence to image the retinal pigment epithelium over the course of a year, this allowed them to map out the direction and magnitude with the geographic atrophy spread. They then found that regions of the choriocapillaris which had less blood flow were more likely to degenerate and become geographic atrophy. Since the choriocapillaris is the main blood supply of the retinal pigment epithelium in the macula, which has no retinal blood supply, it is leading some to believe that geographic atrophy is primarily an ischemic disease (disease due to decreased blood flow).
It was also shown that non-exudative neovascular membranes, which can recapitulate the choriocapillaris, are associated with a markedly slower GA progression. [26] This further supports the vascular insufficiency hypothesis.
Diagnosis of geographic atrophy is made by an ophthalmologist in the clinic. Fundus autofluorescence and optical coherence tomography angiography are imaging modalities that can be used in the diagnosis. While fundus autofluorescence is the standard modality for viewing geographic atrophy, optical coherence tomography can offer unique benefits. Optical coherence tomography angiography can help the physician see if there is any subretinal fluid in the eye. [27] This is useful because it could indicate that the patient may be developing wet AMD. Since patients with geographic atrophy are at higher risk for developing advanced wet AMD (neovascular AMD), this could be especially useful in the monitoring of patients with geography atrophy. If signs of neovascular AMD found, the physician can initiate treatment of wet age-related macular degeneration. [28]
Traditionally, GA progression is quantified in terms of the area of retinal pigment epithelium atrophy. [29] Multiple imaging methods can be applied to quantify this area of retinal pigment epithelium atrophy including short-wavelength (blue) fundus autofluorescence imaging, [30] green fundus autofluorescence imaging, [31] and en face optical coherence tomography imaging. [32]
However, more recent data suggest that photoreceptor degeneration is not limited to the area of retinal pigment epithelium atrophy, but extends beyond this area. These more subtle changes can be quantified by volumetric analyses of optical coherence tomography data. [33] [34]
In February 2023, Apellis Pharmaceuticals received the first FDA approval of pegcetacoplan for the treatment of this condition. [35]
Avacincaptad pegol (Izervay) was approved in the United States in August 2023 for the treatment of geographic atrophy secondary to age-related macular degeneration. [36] [37]
It was recently discovered that the aging pigment lipofuscin can be broken down with the help of melanin and drugs through a newly discovered mechanism (chemical excitation). [38] The pigment lipofuscin plays a central role in the development of dry AMD and geographic atrophy. This breakdown can be supported by medication. This discovery can be translated into the development of a therapy to treat dry AMD.
Macular degeneration, also known as age-related macular degeneration, is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, some people experience a gradual worsening of vision that may affect one or both eyes. While it does not result in complete blindness, loss of central vision can make it hard to recognize faces, drive, read, or perform other activities of daily life. Visual hallucinations may also occur.
Bruch's membrane or lamina vitrea is the innermost layer of the choroid of the eye. It is also called the vitreous lamina or Membrane vitriae, because of its glassy microscopic appearance. It is 2–4 μm thick.
A cone dystrophy is an inherited ocular disorder characterized by the loss of cone cells, the photoreceptors responsible for both central and color vision.
A retinal implant is a visual prosthesis for restoration of sight to patients blinded by retinal degeneration. The system is meant to partially restore useful vision to those who have lost their photoreceptors due to retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Retinal implants are being developed by a number of private companies and research institutions, and three types are in clinical trials: epiretinal, subretinal, and suprachoroidal. The implants introduce visual information into the retina by electrically stimulating the surviving retinal neurons. So far, elicited percepts had rather low resolution, and may be suitable for light perception and recognition of simple objects.
Drusen, from the German word for node or geode, are tiny yellow or white accumulations of extracellular material that build up between Bruch's membrane and the retinal pigment epithelium of the eye. The presence of a few small ("hard") drusen is normal with advancing age, and most people over 40 have some hard drusen. However, the presence of larger and more numerous drusen in the macula is a common early sign of age-related macular degeneration (AMD).
Stargardt disease is the most common inherited single-gene retinal disease. In terms of the first description of the disease, it follows an autosomal recessive inheritance pattern, which has been later linked to bi-allelic ABCA4 gene variants (STGD1). However, there are Stargardt-like diseases with mimicking phenotypes that are referred to as STGD3 and STGD4, and have a autosomal dominant inheritance due to defects with ELOVL4 or PROM1 genes, respectively. It is characterized by macular degeneration that begins in childhood, adolescence or adulthood, resulting in progressive loss of vision.
Sattler's layer, named after Hubert Sattler, an Austrian ophthalmologist, is one of five layers of medium-diameter blood vessels of the choroid, and a layer of the eye. It is situated between the Bruch's membrane, choriocapillaris below, and the Haller's layer and suprachoroidea above, respectively. The origin seems to be related to a continuous differentiation throughout the growth of the tissue and even further differentiation during adulthood.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is an acquired inflammatory uveitis that belongs to the heterogenous group of white dot syndromes in which light-coloured (yellowish-white) lesions begin to form in the macular area of the retina. Early in the course of the disease, the lesions cause acute and marked vision loss that ranges from mild to severe but is usually transient in nature. APMPPE is classified as an inflammatory disorder that is usually bilateral and acute in onset but self-limiting. The lesions leave behind some pigmentation, but visual acuity eventually improves even without any treatment.
Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy commonly exacerbated by extreme myopia, malignant myopic degeneration, or age-related developments.
A maculopathy is any pathological condition of the macula, an area at the centre of the retina that is associated with highly sensitive, accurate vision.
Intraocular hemorrhage is bleeding inside the eye. Bleeding can occur from any structure of the eye where there is vasculature or blood flow, including the anterior chamber, vitreous cavity, retina, choroid, suprachoroidal space, or optic disc.
Macular telangiectasia is a condition of the retina, the light-sensing tissue at the back of the eye that causes gradual deterioration of central vision, interfering with tasks such as reading and driving.
Ron P. Gallemore is a registered ophthalmologist with the American Academy of Ophthalmology involved in research and treatment of diseases of the macula and retina.
Lampalizumab (INN) is an antigen-binding fragment of a humanized monoclonal antibody that binds to complement factor D; it was developed as a potential treatment of geographic atrophy secondary to age-related macular degeneration.
Microperimetry, sometimes called fundus-controlled perimetry, is a type of visual field test which uses one of several technologies to create a "retinal sensitivity map" of the quantity of light perceived in specific parts of the retina in people who have lost the ability to fixate on an object or light source. The main difference with traditional perimetry instruments is that, microperimetry includes a system to image the retina and an eye tracker to compensate eye movements during visual field testing.
Indocyanine green angiography (ICGA) is a diagnostic procedure used to examine choroidal blood flow and associated pathology. Indocyanine green (ICG) is a water soluble cyanine dye which shows fluorescence in near-infrared (790–805 nm) range, with peak spectral absorption of 800-810 nm in blood. The near infrared light used in ICGA penetrates ocular pigments such as melanin and xanthophyll, as well as exudates and thin layers of sub-retinal vessels. Age-related macular degeneration is the third main cause of blindness worldwide, and it is the leading cause of blindness in industrialized countries. Indocyanine green angiography is widely used to study choroidal neovascularization in patients with exudative age-related macular degeneration. In nonexudative AMD, ICGA is used in classification of drusen and associated subretinal deposits.
Conbercept, sold under the commercial name Lumitin, is a novel vascular endothelial growth factor (VEGF) inhibitor used to treat neovascular age-related macular degeneration (AMD) and diabetic macular edema (DME). The anti-VEGF was approved for the treatment of neovascular AMD by the China State FDA (CFDA) in December 2013. As of December 2020, conbercept is undergoing phase III clinical trials through the U.S. Food and Drug Administration’s PANDA-1 and PANDA-2 development programs.
Stem cell therapy for macular degeneration is an emerging treatment approach aimed at restoring vision in individuals suffering from various forms of macular degeneration, particularly age-related macular degeneration (AMD). This therapy involves the transplantation of stem cells into the retina to replace damaged or lost retinal pigment epithelium (RPE) and photoreceptor cells, which are critical for central vision. Clinical trials have shown promise in stabilizing or improving visual function, but are nevertheless inefficient.
Richard Frederick Spaide is an American ophthalmologist and retinal specialist known for his work in retinal diseases and advancements in ocular imaging techniques.
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