Age-Related Macular Degeneration
Age-related macular degeneration (ARMD) is an acquired degeneration of the retina that causes significant central visual impairment through a combination of non-neovascular (drusen and retinal pigment epithelium abnormalities), and neovascular derangement (choroidal neovascular membrane formation). Advanced disease may involve focal areas of retinal pigment epithelium (RPE) loss, subretinal or sub-RPE hemorrhage or serous fluid, as well as subretinal fibrosis. A genetic underpinning is inferred from its predilection to those of European ancestry, although environmental, nutritional, and developmental (ie., aging) processes interact to affect the degeneration observed in the macula. Newly implicated biochemical pathways combined with a paucity of treatment options for the majority of ARMD (i.e.,dry ARMD) has created fertile ground for novel therapeutics.
International Classification of Diseases (ICD)
- 362.51 Nonexudative age-related macular degeneration
- 362.52 Exudative age-related macular degeneration
- H35.31 Nonexudative age-related macular degeneration
- H35.32 Exudative age-related macular degeneration
Drusen and disciform lesions have been observed in conjunction for well over 100 years. The hallmark of age-related macular degeneration is the presence of drusen within the macula. The word druse (singular) is derived from the German word for potato stone or geode.
- Age-related Macular degeneration (ARMD)
- Nonexudative, dry, or non-neovascular ARMD (synonyms)
- Exudative, wet, or neovascular ARMD (synonyms)
- Geographic atrophy
- Choroidal neovascularization and choroidal neovascular membranes
- Early ARMD: Defined by the presence of numerous small (<63 microns, “hard”) or intermediate (≥63 microns but <125 microns, “soft”) drusen. Note: Small drusen are frequently seen in those 50 and older, and can represent an epiphenomenon of aging (therefore, intermediate drusen are more specific for ARMD).
- Intermediate ARMD: Macular disease characterized by either extensive drusen of small or intermediate size, or any drusen of large size (≥125 microns).
124 micron is the average diameter of retinal vein at the optic disc margin.
- Advanced ARMD: Defined by the presence of either geographic atrophy or choroidal neovascular membrane (along with its sequelae, such as subretinal or sub-RPE hemorrhage or serous fluid, and subretinal fibrosis). The figure below demonstrates progressive geographic atrophy over a 29-month period. There is also an area of choroidal neovascularization along the inferior aspect of the scar with subretinal fibrosis that progresses over these 29 months.
Macroeconomic disease burden
The costs of ARMD to society and the patient have been divided into direct costs (direct ophthalmologic cost and direct non-ophthalmogic cost) and indirect costs.  Direct ophthalmologic costs include the cost of treatments (AREDS, intravitreal injections, laser treatment, diagnostic imaging, etc.). Direct non-ophthalmologic costs include special services and equipment such as rehabilitation services, low vision aids and transportation services. Measurement of these costs are more difficult and less pervasive in the literature. Indirect costs include lost productivity and workplace costs. The annual loss of GDP due to neovascular ARMD in one study was calculated to be $5.396 billion, and $24.395 billion for non-neovascular ARMD.
A combination of risk factors interplay to modify the Bruch's membrane/choroid complex, the retinal pigment epithelium and photoreceptor cells. The initiating events affect one, both, or all of these tissue components. A change in one of these tissue components is thought to impart an influence on the others in such a way that an 'intermediate disease mechanism” arises. The degenerating retina succumbs to the final end point of geographic atrophy, choroidal neovascularization and pigment epithelial detachment. Treatments targeting intermediate disease mechanisms or initiating disease factors are in the minority, but may offer a more successful approach to vision preservation than those targeting relatively later steps in ARMD pathophysiology (i.e., choroidal neovascularization).
The prevalence of advanced ARMD in the Beaver Dam Eye Study was 1.6%, with the exudative form being present in one eye 1.2% of the time, and geographic atrophy in one eye 0.6% of the time. This population represented 4,926 people between the ages of 43 to 86 years of age. Similar prevalence data was noted in the Framingham Eye Study, which reported a prevalence of exudative ARMD in those older than 52 years of age of 1.5%. The prevalence of age-related macular degeneration sharply increases in those 75 years or older.
ARMD risk increases with age. The risk increases more than three-fold in patients older than 75 years of age compared to the group of patients between 65-74 years of age (Beaver Dam Eye Study; Framingham Eye Study).
A ten pack-year tobacco smoking history is associated with increased development of exudative age-related macular degeneration. After controlling for confounding factors such as socioeconomic status, alcohol consumption and cardiovascular disease, the rates of visually significant ARMD in smokers and non-smokers over the age of 75 were calculated in an United Kingdom population-based cross sectional study. Current smokers were twice as likely to have ARMD-related vision loss when compared to non-smokers, ex-smokers had a slightly increased risk (odds ratio of 1.13), and those who had stopped smoking over 20 years earlier were not at increased risk for developing vision loss from ARMD.
In addition to increasing one's risk of developing ARMD, certain genetic loci have been associated with variable effects on treatment response, such as intravitreal anti-VEGF agents.
Complement factor H (CFH) is an important gene in the pathogenesis of ARMD.
Pharmacogenomic studies, such as these, may guide treatment regimens in the future, or may at least provide a more accurate prediction of treatment response. Recently, microRNA dysregulation has been linked with the development of ARMD, modulation of which could provide potential treatments for the disease.
Other Risk factors
Cardiovascular disease, Hypertension, Female gender, White race, Hypercholesterolemia, Obesity, Hyperopia, Family History, Light Irides
Pathology Vs. Normal Aging
Normal aging changes can be observed in the outer retina, RPE, Bruch’s membrane, and choriocapillaris, and many of these changes are difficult to separate from those seen in ARMD. In many instances, the designation of normal and abnormal has simply not been established to date. Furthermore, since aging is perhaps one of the most important risk factors for age-related macular degeneration, the physiological changes in aging may mirror the pathophysiological changes in age-related macular degeneration. Cumulative oxidative injury likely underlies changes seen in both aging and ARMD, for example. With age, within the outer retina, the photoreceptors become reduced in density. Within the RPE, melanin granules diminish, and lipofuscin granules form. Sheet-like deposits called basal laminar deposits develop below the RPE but above Bruch’s membrane (basal lamina of the RPE). Within the choriocapillaris, involutional changes are observed. Decreased choroidal blood flow, lumen diameter and choriocapillaris number also occur with aging. Scant, small, hard drusen alone cannot be pathognomonic for age-related macular degeneration, as focal deposition of acellular debris between the RPE and Bruch's membrane is found frequently in aged individuals, and is a normal finding in aging. Age-related drusen, however, are biochemically distinct from drusen associated with ARMD. Large, confluent, or soft drusen are more likely to be a marker of age-related macular degeneration than normal aging.
- Basal laminar deposits- Between RPE and the basement membrane of the RPE. Consists of 'granular lipid-rich material and Widely spaced collagen fibers'
- Basal linear deposits- Within the inner aspect of Bruch's membrane. Consists of 'phospholipid vesicles and electron-dense granules'
Drusen are a hallmark of ARMD. On histopathology, nodular drusen appear as eosinophilic dome-shaped structures situated between Bruch's membrane and the displaced, attenuated RPE overlying the drusen. Drusen display dense PAS-positivity. They may become more basophilic with accumulation of calcium. Von Kossa staining may reveal calcific granules or calcific stippling within such calcified drusen. Soft or large drusen may occur with the development of localized detachments of basal laminar or basal linear deposits, which represent granular material accumulating between either the RPE and its basement membrane or external to the RPE's basement membrane, respectively.  The size and density of drusen are determinant factors in the progression of the disease.
Serous detachments of the RPE
On histopathology, serous RPE detachments can be associated with thickening of the inner aspect of Bruch's membrane.
Histopathologically, RPE atrophy may be associated with depigmentation, migration and proliferation of RPE cells into the photoreceptor layer. With progression, RPE degeneration is seen, with loss of adjacent photoreceptors, and juxtaposition of Bruch's membrane to the inner nuclear layer.
Subretinal or sub-RPE neovascularization
Sub-RPE neovascularization is located within Bruch's membrane, typically between the thickened inner aspect of Bruch's membrane and the rest of Bruch's membrane. A sub-RPE neovascular membrane can extend subretinally in areas where Bruch's membrane is not intact. With discontinuities in Bruch's membrane, capillary-like choroidal vessels can form a subretinal RPE vascular web that can affect serous or hemorrhagic detachments of the neurosensory retina.
Disciform scars or lesions
Fibrous disciform scars are usually results of sub-RPE neovascularization. Fibrous tissue develops within Bruch's membrane or between the RPE and retina. Hemosiderin is typically present, suggesting a hemorrhagic antecedent event. RPE hyperplasia may be a prominent feature of disciform scarring, and lymphocytic infiltrate in the adjacent choroid is occasionally appreciated. Overlying retina undergoes cystic degeneration with photoreceptor loss.
Genetic and Biochemical Pathways in ARMD (see )
Biochemical pathways and genetic association studies have shed light on the possible biochemical pathways that go awry in ARMD. Two polymorphisms, Tyr402His at 10q26 (Complement factor H locus), and Ala69Ser (LOC387715) may be responsible for up to 50-75% of the genetic risk of ARMD. One caveat of these risk alleles is that they have not been validated in racial groups other than Caucasians. Aside from explaining some of the genetic predisposition in ARMD, these loci have uncovered new biochemical pathways hitherto unlinked to ARMD pathogenesis, providing novel therapeutic targets. Pathway-based treatment modalities targeting oxidative damage, lipofuscin accumulation, inflammation, and derangements in complement activation are rapidly proliferating. The following list represents the biochemical pathways implicated in ARMD pathogenesis and the corresponding genetic loci involved.
- Complement pathway (complement factor 2, complement factor 3, complement factor B, complement factor H, complement factor I)
- Extracellular matrix function, cellular anchoring (Fibulin 5 and 6)
- Innate immunity (Toll-like receptor 3 and 4)
- Proteolysis/Drusen metabolism (HTRA1, serine protease)
- DNA repair (ERCC6)
- DNA transcription (RAX2)
- Lipid signaling/metabolism (transporter protein, ABCA4)
- Other (LOC387715, hypothetical gene)
The Complement System
The complement system is a three-pronged pathway involved in natural and acquired immunity. It represents a highly regulated conglomeration of approximately 30 proteins, some of which are cell surface receptors, while others possess catalytic activity. The three prongs of the pathway include the classical, the alternative, and the lectin pathways. The classical pathway depends on activation by antigen-antibody complexes, the lectin pathway, on carbohydrate residues, and the alternative pathway depends on spontaneous activation. Complement activity may increase in response to surface features on microorganisms. Components in cigarette smoke may also trigger this activity. Activation of the complement system results in cellular damage that is central in the pathogenesis of dry and wet forms of ARMD, and this is supported by the presence of many complement system proteins within drusen in patients with ARMD. The alternative pathway becomes activated through a process known as "tickover.” Under normal circumstances, proteins expressed on host cells inhibit this tickover process, and in so doing prevent injury to the host. Instances where this inhibition is jeopardized is when factors favoring activation increase locally (or systemically), inhibitors decrease (or their function decreases), or when there is an increased local concentration of alternative pathway components. Therefore, there needs to be active, continuous control over the alternative pathway to avoid autologous tissue destruction. In ARMD, it is believed that an early "seeding event," such as an area of retinal pigment epithelium atrophy with cellular debris, induces innate immune system activation at the RPE-choroid-Bruch's membrane complex. Subsequently, complement attack (membrane attack complex activation) leads to collateral damage of retinal tissue. This damage predisposes to geographic atrophy and choroidal neovascular membrane formation. In 2005, four groups independently reported that a polymorphism at amino acid position 402 of factor H is associated with ARMD. Factor H is the main soluble inhibitor of the alternative complement pathway. Mutation in factor H in the same region where the polymorphism is encountered has been associated with type II membranoproliferative glomerulonephritis, a condition wherein drusen also develop.
Smoking cessation, reduction in body mass index, and treatment of hypertension are modifiable risk factors that should be addressed in patients at risk for, or who have various stages of ARMD. Based on population based cross sectional studies, the prevalence of ARMD in ex-smokers is less than in smokers, arguing for a possible benefit of smoking cessation on societal ARMD disease burden. Studies on the beneficial effect of dietary antioxidants and omega 3 fatty acids on prevention of AMD have yielded insufficient results.
The diagnosis of early ARMD is typically made after considering a patient's age, physical exam findings, and family history, as many patients in early stages of the disease possess no symptoms.
Decreased central visual acuity may not be present in ARMD, especially in early stages, and is not a reliable indicator of disease severity. In fact, advanced ARMD may be associated with relatively preserved visual acuity (see time lapse fundus photograph above, where a patient had 20/40 vision despite advanced ARMD). Exudative ARMD changes may be associated with acute to subacute drops in vision, or perception of visual distortion such as metamorphopsia.
- Periodic dilated fundus exams are warranted to identify patients who progress to neovascular ARMD without having symptoms.
- Amsler grid
- The Preferential Hyperacuity Perimeter (PreView PHP, Carl Zeiss Meditec, Dublin, CA/ ForeseeHome) is useful, when available, to identify new-onset neovascular ARMD changes.
- Geographic atrophy
- Subretinal fibrosis
- RPE changes
- Subretinal fluid or hemorrhage/hard exudate
- Decreased visual acuity, insidious or sudden-onset
- Dry ARMD constitutes 85-90% cases of ARMD, and usually does not cause severe vision loss.
- Wet AMD constiutes 10-15% of ARMD cases and is the major cause of severe vision loss.
- Blurred vision
- Distorted near vision
- Visual distortion, metamorphopsia, micropsia
- Vague visual complaints
The hallmark findings in nonexudative ARMD are drusen, RPE changes, and geographic atrophy. In advanced ARMD, drusen may fade or become resorbed in areas of geographic atrophy. Large areas of geographic atrophy may show prominent deep choroidal vessels with atrophy of the choriocapillaris.
Fundus Fluorescein Angiography/FFA
Fluorescein angiography and optical coherence tomography are useful in evaluating for the presence of exudative ARMD. Fluorescein angiography is performed when there is suspicion for choroidal neovascular membrane (CNVM) formation. ARMD pathology on fluorescein angiography can be organized into hyperfluorescent changes and hypofluorescent changes. Changes in ARMD that cause hypofluorescent changes are few, and include hemorrhage, lipid exudation, and pigment hyperplasia. Causes of hyperfluorescent lesions are more numerous, and include drusen, RPE atrophy (transmission defects), choroidal neovascular membranes, serous pigment epithelial detachments, and subretinal fibrosis or scars (staining defects). Choroidal neovascular membranes can present differently on angiography. Two main designations are 'classic' vs. 'occult.' Fluorescein angiographic features help distinguish classic choroidal neovascularization and occult choroidal neovascularization. Differences in angiographic patterns are thought to arise from 'classic' lesions penetrating the retinal pigment epithelium, and thus being located in front of the RPE, and 'occult' lesions being sub-RPE. Classic membranes are associated with an early hyperfluorescent area that is well-demarcated, which increases in intensity and extent beyond the early phase boundary by mid- to late-frames. Pooling of fluorescein associated with a concomitant subsensory retinal detachment may also be appreciated.
Occult membranes are presumed when late choroidal leakage is noted without a discernible classic membrane pattern. Occult membranes are also presumed when a fibrovascular pigment epithelial detachment (FVPED) is suspected. FVPEDs are associated with irregular RPE elevation, and a stippled hyperfluorescent pattern with or without leakage or pooling. 
Types of CNVM on FFA
- Classic CNVM- an area of discrete well-defined bright, fairly uniform lacy hyperfluorescence in the early phase (usually near the subretinal bleed) that progressively increases in intensity and size with blurring of the margin of hyperfluorescence (leak)
- Occult CNVM
- a.- Fibrovascular pigment epithelial detachment- Better appreciated with stereoscopic views. At 1-2 minutes, there is an irregular elevation of the RPE with stippled or granular hyperfluorescence . As time passes, the boundary may or may not show leakage. The margin of FVPED may be apparent in around 1-2 minutes of the FFA or the margin may be difficult to ascertain in some cases.
- Late leakage of an undetermined source- In early or mid phase, there is no well-defined area of hyperfluorescence like what is seen with classic CNVM or FVPED. The leakage is usually deep/choroidal or at the RPE and late associated with speckled appearance and pooling of dye in the subretinal space overlying the speckles.
Optical Coherence Tomography/OCT
Optical coherence tomography (OCT) offers a non-invasive, high-resolution, optical cross-sectional method that utilized low-coherence interferometry. OCT has become indispensable in the evaluation of patients with ARMD. Imaging helps evaluate for tomographic sequelae of neovascular membranes, as well as monitor for treatment responses.
Type 1 CNVM= sub-RPE CNVM, usually related to occult CNVM on FFA
Type 2 CNVM= subretinal CNVM (superficial to the RPE), usually corresponds to classic membranes on FFA
Type 3 CNVM= retinal angiomatous proliferation (RAP)
No routine blood tests are available to diagnose ARMD, and although elevated inflammatory markers (e.g., CRP) and certain genetic polymorphisms have been associated with increased risk of developing advanced ARMD, these tests are not routinely employed.
The differential diagnosis of age-related macular degeneration varies greatly depending on whether choroidal neovascularization is present or not, so it is useful to organize the differential into "nonexudative" vs. "exudative" ARMD.
- Exudative ARMD: The differential diagnosis of neovascular ARMD includes choroidal neovascularization caused by conditions other than ARMD, such as ocular histoplasmosis syndrome, pathologic myopia, chroidal rupture, angioid streaks, or idiopathic causes. In addition, foveal detachments or vitelliform detachments may complicate other conditions, such as cuticular drusen, or pattern dystrophies. The latter would not be associated with leakage on fluorescein angiography, but rather progressive staining of vitelliform material. Polypoidal choroidal vasculopathy may produce hemorrhagic PEDs that can resemble those in ARMD, but the absence of drusen, the often peripapillary location of such lesions, and the better visual acuity outcomes of polypoidal vasculopathy help distinguish it from ARMD. Choroidal tumors obscured by subretinal hemorrhage or RPE changes may also masquerade for exudative ARMD, but unilaterality and ultrasonography should help distinguish a tumor from ARMD. Central serous retinopathy is an important differential especially of occult CNVM.
- Nonexudative ARMD: The differential diagnosis of non-neovascular ARMD includes retinal pigment epithelial changes secondary to central serous chorioretinopathy (CSC), pattern dystrophy, cuticular drusen, and drug toxicity (e.g., chloroquine toxicity). These conditions overlap with the various pathological changes observed in dry ARMD, but either occur in a younger patient population, or are missing key ARMD features, such as drusen. For example, CSC may present with multiple serous PEDs and RPE changes, but not drusen. Pattern dystrophy usually affects patients younger in age than ARMD, and has a fluorescein angiography pattern that is distinct, with early blocked fluorescence with surrounding hyperfluorescence, and late staining of the vitelliform material.
Observation with risk factor modification and nutritional supplementation is the mainstay of treatment for nonexudative ARMD. However, current studies are underway to evaluate complement pathway inhibition for the treatment of geographic atrophy in patients with nonexudative ARMD though no treatment modality is currently approved by the FDA for the treatment of geographic atrophy. Exudative ARMD is managed with more closely spaced examinations and intravitreal injections of anti-VEGF agents or laser treatments. Patients with advanced disease in both eyes should undergo evaluation and rehabilitation with low-vision services.
Non-neovascular ARMD Treatments
Antioxidant and mineral supplementation
Antioxidant and mineral supplementation has been shown to reduce the risk of progression in ARMD. The daily amounts of antioxidants and zinc in the AREDS formulation is :
- 500 milligrams of vitamin C
- 400 International Units of vitamin E
- 15 milligrams of beta-carotene (equivalent of 25,000 International Units of vitamin A)
- 80 milligrams of zinc as zinc oxide
- 2 milligrams of copper as cupric oxide
Since, high dose zinc supplementation can lead to a copper-deficiency anemia by inhibiting copper absorption at the level of the enterocyte, copper supplementation was added to the AREDS formula. Cigarette smokers should be warned about the small, but real potential risk of lung cancer with high dose beta-carotene supplementation in the AREDS formula. Non-beta-carotene-containing supplements are more appropriate for this subgroup of patients. 
Based on data suggesting that increasing intake of lutein + zeaxanthin, and omega-3 long-chain polyunsaturated fatty acids (docosahexaenoic acid [DHA] + eicosapentaenoic acid [EPA]) might reduce the risk of developing advanced AMD, AREDS2, a randomized, double-masked control trial was started. AREDS2 was designed to test whether adding lutein + zeaxanthin, DHA + EPA, or lutein + zeaxanthin + DHA + EPA to the AREDS formulation further reduces the risk of progression to advanced AMD. Another goal of AREDS was to test the effects of eliminating beta carotene and reducing the zinc dose from the AREDS formulation. The following are the modifications of AREDS2:
- 10 mg lutein and 2 mg zeaxanthin
- 350 mg DHA and 650 mg EPA
- No beta-carotene
- 25 mg zinc
In AREDS2, lutein/zeaxanthin or DHA/EPA had no additional effect on the risk of advanced AMD. Study participants who took AREDS containing lutein/zeaxanthin and no beta-carotene had a slight reduction in the risk of advanced AMD, compared to those who took AREDS with beta-carotene and no lutein/zeaxanthin. Importantly, former smokers who took AREDS with beta-carotene had a higher incidence of lung cancer. Lower zinc oxide doses (25mg) did not significantly increase the risk of advanced AMD, although a trend to more protection from advanced AMD was noted with higher zinc oxide doses (80mg). Newer formulations replace beta-carotene with lutein/zeaxanthin, but keep the zinc oxide dose the same.
- 500 milligrams of vitamin C
- 400 International Units of vitamin E
- 80 milligrams of zinc as zinc oxide
- 2 milligrams of copper as cupric oxide
- 10 mg lutein and 2 mg zeaxanthin
- No beta-carotene
Complement Factor Inhibitors
The complement factor 3 inhibitor pegcetacoplan has been assessed for the treatment of the geographic atrophy in the phase 3 DERBY and OAKS trials. In the DERBY trial, monthly dosing of pegcetacolplan led to a 36% decrease in lesion growth, while every other month dosing of pegcetacolplan led to a 29% decrease in lesion growth at 24 months. The OAKS trial showed a 24% decrease in GA growth with every month dosing, and a 25% decrease in lesion growth with every other month dosing. No clinically meaningful differences were noted on functional outcomes. The data also revealed an increased risk of development of neovascular ARMD.
Neovascular ARMD Treatments
Macular Photocoagulation Studies
Studies performed in the 1980's assessed the efficacy of laser photocoagulation in limiting damage caused by choroidal neovacular lesions. These studies evaluated laser treatment of extrafoveal, juxtafoveal, and subfoveal neovascular membranes. Patients with direct laser photocoagulation to extrafoveal or juxtafoveal sites fared better than those receiving direct laser to subfoveal membranes. While severe vision loss was averted, laser photocoagulation currently has limited utility because of its high recurrence rates, risk of inducing vision loss (especially with subfoveal membranes), and failure to affect an improvement in vision from baseline visual acuity. In the era of anti-VEGF therapies, the indications for direct photocoagulation are diminishing.
However, it may be considered in extrafoveal small CNVM.
verteporfin Photodynamic therapy/vPDT
Use of photosensitizers (e.g., verteporfin) that pool in neovascular membranes and subsequently produce reactive oxygen species upon activation with light of a specific wavelength was introduced in the late 1990's. In the era of anti-VEGF therapies, the indications for photodynamic therapy are diminishing.
However, PDT has a definite role in the management of polypoidal choroidal vasculopathy and central serous chorioretinopathy. EVEREST trial showed that 'after 12 months, combination therapy of ranibizumab plus vPDT was not only noninferior but also superior to ranibizumab monotherapy in best-corrected visual acuity and superior in complete polyp regression while requiring fewer injections'
Optical coherence tomography and anti-vascular endothelial growth factor (VEGF) therapy together have revolutionized the treatment of exudative ARMD. Ranibizumab (Lucentis, Genentech, San Francisco, CA), bevacizumab (Avastin, Genentech, San Francisco, CA), and aflibercept (Eylea, Regeneron Pharmaceuticals Inc., Tarrytown, NY), are frequently used in the treatment of exudative ARMD. Pegaptanib (Macugen, Pfizer) was the first anti-VEGF therapy to recieive FDA approval for the treatment of ARMD in 2004. It is biochemically distinct from subsequent anti-VEGF agents, in that it represents an aptamer as opposed to a monoclonal antibody (bevacizumab), monoclonal antibody fragment (ranabizumab), or a receptor-antibody fusion protein (aflibercept, see diagram below). Pegaptanib is a small oligonucleic acid molecule that binds specifically to the VEGF-165 isoform. The most recent anti-VEGF agent that was recently approved was brolucizumab (Beovu, Novartis, Cambridge, MA), which is a single chain antibody fragment against VEGF, which was found to be non-inferior to aflibercept, and more than half of patients were able to extend to 3 months dosing with brolucizumab within the first year as demonstrated in the HAWK and HARRIER trials.
In an effort to extend dosing, a new port delivery system was developed by Genentech to deliver continuous levels of ranibizumab. The ranibizumab port delivery system (Susvimo, Genentech, San Francisco, CA) is a unique surgical implant that is placed within the vitreous and provides continuous delivery of ranibizumab. This implant was approved by the FDA in October 2021, and this delivery system can be refilled every 6 months. The Archway study showed non-inferiority of the port delivery system compared to monthly ranibizumab injections. 98% of patients were able to go 6 months before their first refill.
Radiotherapy has been used in neovascular ARMD under the premise that radiation can inhibit the exuberant cellular proliferation necessary to create the choroidal neovascular membrane. However, studies on efficacy have not shown a clear benefit of this treatment modality.
Anti-VEGF and Anti-Ang2 treatment
The first bi-specific antibody therapy for the treatment of neovascular ARMD was recently approved by the FDA on January 31, 2022. Faricimab (Vabysmo, Genentech, San Francisco, CA) is a bi-specific antibody directed against both VEGF and angiopoietin-2. This dual targeted treatment was dosed up to 4 month intervals and was found to be non-inferior to aflibercept given every 2 months in the first year. In the TENAYA and LUCERNE trials, a large majority of patients could be dosed at 3 months intervals or more, showing improved efficacy and durability of the treatment compared to the anti-VEGF inhibition alone.
Treatments targeting biochemical pathways implicated in the pathophysiology of ARMD are being tested actively in clinical trials. Agents currently undergoing evaluation in geographic atrophy /advanced AMD are listed in the table below. Treatments include small inhibitory RNA molecules, monoclonal antibodies, gene therapy, anti-inflammatory medications, antioxidants, and cell-based therapies.
Information for the following table was retrieved from http://clinicaltrials.gov on 8/2019.
|Investigational agent||Route of administration||Mechanism of action||Targeted Pathology||Clinical Trial Identification||Sponsoring company/institution||Study status||Phase of study|
|Minocycline||Oral||Inhibition of microglia||Geographic atrophy||NCT02564978||NEI||Recruiting||2|
|RC28-E||Intravitreal||Anti-VEGF and Anti-FGF2||Neovascular ARMD||NCT03777254||Remegen||Recruiting||1|
|OpRegen||Subretinal||hESC derived RPE||Geographic atrophy||NCT02286089||Biotime Inc, CellCure Neurosciences||Recruiting||1, 2a|
|AAVCAGsCD59||Intravitreal||Gene therapy based expression of sCD59||Neovascular ARMD||NCT03585556||Hemera Biosciences||Recruiting||1|
|ADVM-022||Intravitreal||Gene therapy based expression of anti-VEGF agent aflibercept||Neovascular ARMD||NCT03748784||Adverum Biotechnologies, Inc.||Recruiting||1|
|Elamipretide||Subcutaneous||Mitochondrially targeted anti-oxidant||Geographic atrophy||NCT03891875||Stealth BioTherapeutics Inc.||Recruiting||2|
|RGX-314||Intravitreal||Gene therapy based expression of anti-VEGF||Neovascular ARMD||NCT03066258||Regenxbio Inc.||Recruiting||1,2a|
|DE-122||Intravitreal||Antibody to endoglin||Neovascular ARMD||NCT03211234||Santen Inc.||Recruiting||2|
|KSI-301||Intravitreal||Polymer conjugate anti-VEGF antibody||Neovascular ARMD||NCT03790852||Kodiak Sciences Inc.||Recruiting||1b|
|APL-2||Intravitreal||Inhibitor of Complement C3||Geographic Atrophy||NCT03525613||Apellis Pharmaceuticals, Inc.||Recruiting||3|
|ALK-001||Oral||Modified Vitamin A||Geographic Atrophy||NCT03845582||Alkeus Pharmaceuticals, Inc.||Recruiting||3|
Submacular surgery in ARMD has included approaches to translocate the macula, either by vitrectomy and retinotomy or by vitrectomy and sclerochroidal foreshortening (achieved externally), yet these procedures have not gained widespread use.  In instances where a large submacular hemorrhage occurs, pneumatic displacement with face-down posititioning and intraocular gas injection can be performed. Some have used vitrectomy, retinotomy, and subretinal injection of tissue plasminogen activator (tPA) in instances of large submacular hemorrhage. The NEI-funded Submacular Surgery Trials (SST) evaluated the visual acuity outcome and complications of excising choroidal neovascular membranes. In patients with large central macular, subretinal hemorrhage due to choroidal neovascularization (new or recurring after laser photocoagulation; Group B protocol), there were no significant difference in BCVA between the surgery and observation arms of the study. The surgical intervention can vary from patient to patient, but had the goal of removing the entire neovascular membrane, any blood, and any scar tissue present. 
Subretinal hemorrhage can cause photoreceptor damage as the blood is in contact with the photoreceptors and early treatment is needed. Subretinal hemorrhage may be of varying severity. Massive subretinal hemorrhages are typically thought to be associated with anticoagulation therapy, specifically, warfarin therapy. Surgical management options has been reviewed elsewhere (Management of Submacular Hemorrhage).
Break-through vitreous hemorrhage secondary to neovascular ARMD is a rare complication. Sudden peripheral visual field and central vision loss is noted in these instances, to be distinguished from the central field complaints typically noted with ARMD. Other etiologies, such as retinal tears from hemorrhagic posterior vitreous detachments, retinal vascular diseases such as diabetic retinopathy or vein occlusions should be considered as well.
Diplopia can occur as a result of the choroidal neovascular membrane "dragging" the fovea. Such patients present with central binocular diplopia in the presence of peripheral fusion. This syndrome is referred to as dragged-fovea diplopia syndrome, and is usually addressed with some form of partial monocular occlusion (Scotch Satin tape).
Severe central vision loss leading to legal blindness (Visual acuity less than 20/200) is an endpoint more frequently seen in neovascular ARMD compared to nonneovascular ARMD. Based on data from the Framingham Eye Study and a case-control study by Hyman et al., the proportions of neovascular and nonneovascular ARMD in patients legally blind in an eye from advanced ARMD were compared. 79% to 90% of legal blindness in advanced ARMD was associated with neovascular, and not nonneovascular disease.
- Boyd K, Gregori NZ, Turbert D. Age-Related Macular Degeneration. American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/diseases/age-related-macular-degeneration-list. Accessed November 17, 2022.
- Porter D, Vemulakonda GA. Drusen. American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/diseases/drusen-list. Accessed November 17, 2022.
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