Age-related macular degeneration

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Age-related macular degeneration
Classification and external resources

Fundus photo and fluorescein angiogram of a classic choroidal neovascular membrane in exudative age-related macular degeneration.

ICD-10 H35.3
ICD-9 362.51

362.52

OMIM 603075
MedlinePlus 001000


Age-releated macular degeneration is an acquired degeneration of the retina that causes significant central visual impairment through a combination of nonneovascular (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.


For a brief, patient-friendly, summary of age-related macular degeneration check out geteyesmart.org

Contents

Disease Entity

International Classification of Diseases (ICD)

  • ICD-9-CM
  1. 362.51 Nonexudative age-related macular degeneration
  2. 362.52 Exudative age-related macular degeneration
  • ICD-10-CM
  1. H35.31 Nonexudative age-related macular degeneration
  2. H35.32 Exudative age-related macular degeneration


Disease

History

Drusen and disciform lesions have been observed in conjunction for well over 100 years.[1]  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.[2] 

Key Terms

  • Age-related Macular degeneration (ARMD)
  • Nonexudative, dry, or nonneovascular ARMD (synonyms)
  • Exudative, wet, or neovascular ARMD (synonyms)
  • Geographic atrophy
  • Choroidal neovascularization and choroidal neovascular membranes


Classification

  • Early ARMD: Defined by the presence of numerous small (<63 microns, “hard”) or intermediate (≥63 microns but <125 microns, “soft”) drusen. Note: Smal drusen are frequently seen in those 50 and older, and can represent an epiphenomenon of aging (therefore, intermediate drusen are more specific for ARMD).[3][4]
  • Intermediate ARMD: Macular disease characterized by either extensive drusen of small or intermediate size, or any drusen of large size (≥125 microns).[5]
  • 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).[6] 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 this 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. [7] 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.[8]  Measurement of these costs are more diffcult and less pervasive in the literature.  Indirect costs include lost productivity and workplace costs.[9] The annual loss of GDP due to neovascular ARMD in one study was calculated to be $5.396 billion, and $24.395 billion for nonneovascular ARMD.[10] 

Etiology

A combination of risk factors interplay to modify the Bruch 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[7]. 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).[7]

Prevalence

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.[11]  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%.[12] The prevalence of age-related macular degeneration sharply increases in those 75 years or older.[13]

Risk Factors

Age

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).[14][15] 

Cigarette Smoking

A ten pack-year tobacco smoking history is associated with increased development of exudative age-related macular degeneration.[16][17] 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.[18]  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.[19]

Genetic susceptibility

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.[20]Pharmacogenomic studies, such as these, may guide treatment regimens in the future, or may at least provide a more accurate prediction of treatment response.  

Other Risk factors

Cardiovascular disease, Hypertension, Female gender, Hypercholesterolemia, Obesity, Hyperopia[21], Family History, Light Irides

General Pathology

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.[22] 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.[23]  With age, within the outer retina, the photoreceptors become reduced in density. Within the RPE, melanin granules diminish, and lipofuscin granules form.[24][25] Sheet-like deposits called basal laminar deposits develop below the RPE but above Bruch’s membrane. Within the choriocapillaris, involutional changes are observed.  Decreased choroidal blood flow, lumen diameter and choriocapillaris number also occur with aging.[26] 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.[27][28][29]  Age-related drusen, however, are biochemically distinct from drusen associated with ARMD.[30]   Large, confluent, or soft drusen are more likely to be a marker of age-related macular degeneration than normal aging.[31]

Drusen

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. [32]

Serous detachments of the RPE

On histopathology, serous RPE detachments can be located within Bruch's membrane, and can be associated with thickening of the inner aspect of Bruch's membrane.[33]

RPE atrophy

Histopathologically, RPE atrophy may be associated with depigmentation, migration and proliferation of RPE cells into the photoreceptor layer.  With progressioin, RPE degeneration is seen, with loss of adjacent photoreceptors, and juxtaposition of Bruch's memrane to the inner nuclear layer.[34]  

Subretinal 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 effect serous or hemorrhagic detachments of the neurosensory retina.[35]

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.[36]  

Pathophysiology

Genetic and Biochemical Pathways in ARMD (see [37])

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 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.[38]  The following list represents the biochemical pathways implicated in ARMD pathogenesis and the corresponding genetic loci involved.



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.[64]  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-Bruchs membrane complex.[65]  Subsequently, complement attack (membrane attack comlex 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.[66][67][68][69]  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.[70]  

Primary prevention

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.[71]   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.[72] 

Diagnosis

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.   

History

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.

Physical examination

  • Periodic dilated fundus exams are warranted to identify patients who progress to neovascular ARMD without having symptoms.  
  • Amsler grid


Hypothetical neovascular ARMD change on an Amsler grid.

en.wikipedia.org/wiki/File:Amslergrid_patientAMD.gif


Signs

  • Drusen
  • Geographic atrophy
  • Subretinal fibrosis
  • RPE changes
  • Subretinal fluid or hemorrhage




Symptoms[74]

  • Decreased visual acuity, insidious or sudden-onset 
  • Blurred vision
  • Distorted near vision
  • Scotoma
  • Visual distortion, metamorphopsia, micropsia
  • Vague visual complaints


Clinical diagnosis

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.  


Diagnostic procedures

Fluorescein Angiography

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 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).[75] Choroidal neovascular membranes can present differently on angiography.  Two main designations are 'classic' vs. 'occult.'  Fluorescein angioraphic 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.[76]  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 concomittant 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 hyperfluorsescent pattern with or without leakage or pooling.[77]


Optical Coherence Tomography

Optical coherence tomography (OCT) offers a non-invasive, high-resolution, optical cross-sectional method that utilized low-coherence interferometry.[78]  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.  



Laboratory tests

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.

Differential diagnosis

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, pathlogic myopia, chroidal rupture, angioid streaks, or idiopathic causes.[7]  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.[7]  Polypoidal choroidal vasculopathy may produce hemorrhagic PEDs that can resemble those in ARMD, but the abscence of drusen, the often peripapillary location of such lesions, and the better visual acuity outcomes of polypoidal vasculopathy help distinguish it from ARMD.[79]  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.[80]

 

  • Nonexudative ARMD: The differential diagnosis of nonneovascular ARMD includes 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.   

Management

Observation with risk factor modification and nutritional supplementation is the mainstay of treatment for nonexudative ARMD.  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.[81]


Medical therapy

Nonneovascular 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[82][83]:

  • 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. Future studies aim to determine whether the benefit of the AREDS formula is jeopardized with lower doses of zinc (40mg), and perhaps if lower doses of zinc will obviate the need for copper supplementation.[84] 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. [85]


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[86][87].  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 effect an improvement in vision from baseline visual acuity.  In the era of anti-VEGF therapies, the indications for direct photocoagulation are diminishing.


Photodynamic therapy

Use of photosensitizers (e.g., verteporfin) that pool in neovascular membranes and subsequently amass reactive oxygen species upon infrared light activation was introduced in the late 1990's.  In the era of anti-VEGF therapies, the indications for photodynamic therapy are diminishing.    


Anti-VEGF treatments

Optical coherence tomography and anti-vascular endothelial growth factor (VEGF) therapy together have revolutionized the treatment of exudative ARMD. Ranabizumab (Lucentis, Genentech, San Francisco, CA), Bevacizumab (Avastin, Genentech, San Francisco, CA), and more recently, 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. 





Radiation therapy

Radiotherapy has been used in neovascular ARMD under the premise that radiation can inhibit the exhuberant cellular proliferation necessary to create the choroidal neovascular membrane.  However, studies on efficacy have not shown a clear benefit of this treatment modality.[88]


Emerging Treatments

Treatments targeting biochemical pathways implicated in the pathophysiology of ARMD are being tested actively in clinical trials.[89][90] Agents currently undergoing evaluation in geographic atrophy /advanced AMD are listed in the table below. Treatments include small inhibitory RNA molecules, monoclonal antibodies, inhibitors of G-protein coupled receptors, anti-inflammatory medications, antioxidants, and cell-based therapies.


Information for the following table was retrieved from http://clinicaltrials.gov on 05/2012.[91]  

Investigational agent Route of administration Mechanism of action Targeted Pathology Clinical Trial Identification Sponsoring company/institution Study status Phase of study
CNTO2476 Subretinal injection Human umbilical tissue derived cells Geographic atrophy NCT01226628 Centocor, Inc. Recruiting 1, 2a
MA09-hRPE Subretinal injection Cell-based therapy Advanced dry ARMD NCT001344993 Advanced Cell Technology Recruiting 1,2
Eculizumab Intravitreal MAb against complement factor C5 Geographic atrophy NCT00935883 Philip J. Rosenfeld, MD, PhD and Alexion Pharmaceuticals Completed 2
LFG316 Intravitreal Geographic atrophy NCT01527500 Novartis Recruiting 2
GSK933776 Intravenous infusion mAb against beta amyloid Geographic atrophy NCT01342926 Glaxosmith Kline Recruiting 2
OT-551 Topical drops Antioxidant Geographic atrophy NCT00306488 NEI, Othera Pharmaceuticals Completed 2
RN6G Intravenous  Systemic anti-amyloid drug Geographic atrophy NCT01577381 Pfizer Not yet open 2
Fluocinolone Acetonide Intravitreal Anti-inflammatory Geographic atrophy NCT00695318 Alimera Sciences Recruiting 2
Brimonidine tartrate implant Intravitreal implant Alpha-2-antagonist Geographic atrophy NCT00658619 Allergan Ongoing 2
FCFD45145 Intravitreal mFab anti Factor D Geographic atrophy NCT01229215 Genentech Ongoing 2
RNA-144101 Intravitreal Inhibitor of TLR3 Geographic atrophy NCT01093170 University of Kentucky Not yet open
E10030 Intravitreal Anti-PDGF Pegylated Aptamer Neovascular ARMD NCT01089517 Ophthotech Corporation Completed 2


Surgery

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. [92]  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. [93]

Complications

Subretinal hemorrhage  

Subretinal hemorrhage may be of varying severity.  Massive subretinal hemorrhages are typically thought to be associated with anticoagulation therapy, specifically, warfarin therapy.[94]  Surgical management options has been reviewed elsewhere (Management of Submacular Hemorrhage).

Vitreous 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.[7]

Diplopia

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).[95] 

Legal blindness

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[96] and a case-control study by Hyman et al.[97], the proportions of neovascular and nonneovascular ARMD in patients legally blind in an eye from advanced ARMD were compared.[7]  79% to 90% of legal blindness in advanced ARMD was associated with neovascular, and not nonneovascular disease.[98]

Additional Resources

American Academy of Ophthalmology http://www.aao.org

Clinicaltrial.gov-U.S. National Institutes of Health http://clinicaltrials.gov

Retinal information network https://sph.uth.tmc.edu/retnet/

Webvision http://webvision.med.utah.edu/book/part-xii-cell-biology-of-retinal-degenerations/age-related-macular-degeneration-amd/

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Original article contributed by: Yasser M. Elshatory, MD
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