Macular degeneration Classification and external resources
ICD-10	H35.3
ICD-9	362.50
MeSH	D008268

Macular degeneration is a medical condition predominantly found in elderly adults in which the center of the inner lining of the eye, known as the macula area of the retina, suffers thinning, atrophy, and in some cases, bleeding. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow" is an oval Yellow spot near the center The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Atrophy is the partial or complete Wasting away of a part of the Body. This can result in loss of central vision, which entails inability to see fine details, to read, or to recognize faces. According to the American Academy of Ophthalmology, it is the leading cause of central vision loss (blindness) in the United States today for those over the age of fifty years. The American Academy of Ophthalmology ( AAO) is a Medical association of ophthalmologists &ndash medical doctors (MDs specializing in eye Blindness is the condition of lacking Visual perception due to Physiological or Neurological factors The United States of America —commonly referred to as the ^[1] Although some macular dystrophies that affect younger individuals are sometimes referred to as macular degeneration, the term generally refers to age-related macular degeneration (AMD or ARMD).

Contents 1 Age-related macular degeneration 1.1 Risk factors 1.2 Signs 1.3 Symptoms 1.4 Diagnosis 1.5 Prevention 2 Juvenile macular degeneration 3 Impact 4 References 5 External links

Age-related macular degeneration

Age-related macular degeneration begins with characteristic yellow deposits in the macula (central area of the retina which provides detailed central vision, called fovea) called drusen between the retinal pigment epithelium and the underlying choroid. Drusen (singular "druse" are tiny yellow or white accumulations of extracellular material that build up in Bruch's membrane of the Eye. The retinal pigment epithelium ( RPE) is the Pigmented cell layer just outside the neurosensory Retina that nourishes retinal visual cells and is firmly The choroid, also known as the choroidea or choroid coat, is the vascular layer of the Eye lying between the Retina and the Sclera Most people with these early changes (referred to as age-related maculopathy) have good vision. People with drusen can go on to develop advanced AMD. The risk is considerably higher when the drusen are large and numerous and associated with disturbance in the pigmented cell layer under the macula. Recent research suggests that large and soft drusen are related to elevated cholesterol deposits and may respond to cholesterol lowering agents or the Rheo Procedure.

Advanced AMD, which is responsible for profound vision loss, has two forms: dry and wet. Central geographic atrophy, the dry form of advanced AMD, results from atrophy to the retinal pigment epithelial layer below the retina, which causes vision loss through loss of photoreceptors (rods and cones) in the central part of the eye. While no treatment is available for this condition, vitamin supplements with high doses of antioxidants, lutein and zeaxanthin, have been demonstrated by the National Eye Institute and others to slow the progression of dry macular degeneration and in some patients, improve visual acuity. As a pigment This Xanthophyll, like its sister compound Zeaxanthin, has primarily been used as a natural colorant due to its Orange-red Color Zeaxanthin is one of the two Carotenoids contained within the Retina of the Eye.

Neovascular or exudative AMD, the wet form of advanced AMD, causes vision loss due to abnormal blood vessel growth in the choriocapillaries, through Bruch's membrane, ultimately leading to blood and protein leakage below the macula. Neovascularization is the formation of functional microvascular networks with red blood cell perfusion An exudate is any Fluid that filters from the Circulatory system into Lesions or areas of Inflammation. Bruch's membrane is the innermost layer of the Choroid. It is also called the vitreous lamina, because of its glassy microscopic appearance Bleeding, leaking, and scarring from these blood vessels eventually cause irreversible damage to the photoreceptors and rapid vision loss if left untreated.

Until recently, no effective treatments were known for wet macular degeneration. However, new drugs, called anti-angiogenics or anti-VEGF (anti-Vascular Endothelial Growth Factor) agents, when injected directly into the vitreous humor of the eye using a small, painless needle, can cause regression of the abnormal blood vessels and improvement of vision. Anti-angiogenics is a class of Drug that prevents the formation of abnormal new Blood vessels in the Eye, and dries up vessels which have already begun Vascular endothelial growth factor ( VEGF) a sub-family of Growth factors, more specifically of Platelet-derived growth factor family of cystine-knot growth The injections frequently have to be repeated on a monthly or bi-monthly basis. Examples of these agents include Lucentis, Avastin and Macugen. Ranibizumab (trade name Lucentis) is a Monoclonal antibody fragment derived from the same parent murine antibody as Bevacizumab (Avastin Bevacizumab (Avastin Genentech/Roche is a Monoclonal antibody against Vascular endothelial growth factor (VEGF Pegaptanib sodium injection (brand name Macugen) is an anti-angiogenic medicine for the treatment of neovascular (wet Age-related macular degeneration Only Lucentis and Macugen are FDA approved as of April 2007. Macugen has been found to have only minimal benefits in neovascular AMD and is no longer used. Worldwide, Avastin has been used extensively despite its "off label" status. Off-label use is the practice of prescribing drugs for a purpose outside the scope of the drug's approved label most often concerning the drug's indication. The cost of Lucentis is approximately $2000 US per treatment while the cost of Avastin is approximately $150 per treatment. Lucentis is a close chemical relative of Avastin. Both drugs are made by Genentech.

Risk factors

• Aging: Approximately 10% of patients 66 to 74 years of age will have findings of macular degeneration. The prevalence increases to 30% in patients 75 to 85 years of age.
• Family history: The lifetime risk of developing late-stage macular degeneration is 50% for people who have a relative with macular degeneration vs. 12% for people who do not have relatives with macular degeneration, i. e. a fourfold higher risk.
• Macular degeneration gene: The genes for the complement system proteins factor H (CFH) and factor B (CFB) have been determined to be strongly associated with a person's risk for developing macular degeneration. The complement system is a Biochemical cascade that helps clear Pathogens from an organism Factor H is a member of the regulators of complement activation family and is a Complement control protein. CFH is involved in inhibiting the inflammatory response mediated via C3b (and the Alternative Pathway of complement) both by acting as a cofactor for cleavage of C3b to its inactive form, C3bi, and by weakening the active complex that forms between C3b and factor B. The alternative pathway of the Complement system is a humoral component of the Immune system 's natural defense against infections which can operate without antibody C-reactive protein and polyanionic surface markers such as glycosaminoglycans normally enhance the ability of factor H to inhibit complement . Glycosaminoglycans (GAGs or mucopolysaccharides are long unbranched Polysaccharides consisting of a repeating Disaccharide unit But the mutation in CFH(Tyr402His) reduces the affinity of CFH for CRP and probably also alters the ability of factor H to recognise specific glycosaminoglycans. This change results in reduced ability of CFH to regulate complement on critical surfaces such as the specialised membrane at the back of the eye and leads to increased inflammatory response within the macula. In two 2006 studies at Yale Department of Epidemiology and Public Health and the Department of Ophthalmology and Visual Sciences, Moran Eye Center at the University of Utah School of Medicine, another gene that has implications for the disease, called HTRA1 (encoding a secreted serine protease), was identified. ^[2][3]
• Arg80Gly variant of the complement protein C3 A genetic study published in the New England Journal of Medicine in 2007 showed that a certain, common mutation in the C3 gene which is a central protein of the complement system is strongly associated with the occurrence of Age-related Macular Degeneration. The complement system is a Biochemical cascade that helps clear Pathogens from an organism The complement system is a Biochemical cascade that helps clear Pathogens from an organism ^[4] The authors consider their study to underscore the influence of the complement pathway in the pathogenesis of this disease.
• Hypertension: Also known as high blood pressure. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated
• Cardiovascular status — high cholesterol, obesity. Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected
• High fat intake is associated with an increased risk of macular degeneration in both women and men. Fat provides about 42% of the food energy in the average American diet. Food energy is the amount of Energy in food that is available through Digestion. A diet that derives closer to 20-25% of total food energy from fat is probably healthier. Reducing fat intake to this level means cutting down greatly on consumption of red meats and high-fat dairy products such as whole milk, cheese, and butter. Eating more cold-water fish^[5] (at least twice weekly), rather than red meats, and eating any type of nuts may help macular degeneration patients. ^[6]
• Oxidative stress: It has been proposed that age related accumulation of low molecular weight, phototoxic, pro-oxidant melanin oligomers within lysosomes in the retinal pigment epithelium may be partly responsible for decreasing the digestive rate of photoreceptor outer rod segments (POS) by the RPE. Pro-oxidants are chemicals that induce Oxidative stress, either through creating Reactive oxygen species or inhibiting Antioxidant systems Melanin is a class of compounds found in the Plant, Animal and Protista kingdoms, where it serves predominantly as a Pigment. The retinal pigment epithelium ( RPE) is the Pigmented cell layer just outside the neurosensory Retina that nourishes retinal visual cells and is firmly A decrease in the digestive rate of POS has been shown to be associated with lipofuscin formation - a classic sign associated with macular degeneration. Lipofuscin is the name given to finely granular yellow brown Pigment granules composed of Lipid -containing residues of Lysosomal digestion ^[7][8]

• Fibulin-5 mutation Rare forms of the disease are caused by geneic defects in fibulin-5, in an autosomal dominant manner. In 2004 Stone et al performed a screen on 402 AMD patients and revealed a statistically significant correlation between mutations in Fibulin-5 and incidence of the disease. Furthermore the point mutants were found in the Calcium binding sites of the cbEGF domains of the protein. there is no structural basis for the effects of the mutations.

• Race Macular degeneration is more likely to be found in whites than in blacks. ^[9][10]
• Exposure to sunlight especially blue light. There is conflicting evidence as to whether exposure to sunlight contributes to the development of macular degeneration. A recent study in the British Journal of Ophthalmology on 446 subjects found that it does not. ^[11] High-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration. In Ophthalmology, high-energy visible light ( HEV light) is high-frequency light in the violet / Blue band from 380 to 530  nm in ^[12][13][14]

Signs

• Drusen
• Pigmentary alterations
• Exudative changes: hemorrhages in the eye, hard exudates, subretinal/sub-RPE/intraretinal fluid
• Atrophy: incipient and geographic
• Visual acuity drastically decreasing (two levels or more) ex: 20/20 to 20/80. Drusen (singular "druse" are tiny yellow or white accumulations of extracellular material that build up in Bruch's membrane of the Eye. Bleeding, technically known as hemorrhaging / haemorrhaging (see American and British spelling differences) is the loss of Blood from

Symptoms

• Blurred vision: Those with nonexudative macular degeneration may by asymptomatic or notice a gradual loss of central vision, whereas those with exudative macular degeneration often notice a rapid onset of vision loss.
• Central scotomas (shadows or missing areas of vision)
• Distorted vision (i. e. metamorphopsia) - A grid of straight lines appears wavy and parts of the grid may appear blank. Patients often first notice this when looking at mini-blinds in their home.
• Trouble discerning colors; specifically dark ones from dark ones and light ones from light ones.
• Slow recovery of visual function after exposure to bright light

The Amsler Grid Test is one of the simplest and most effective methods for patients to monitor the health of the macula. The Amsler Grid is essentially a pattern of intersecting lines (identical to graph paper) with a black dot in the middle. The Amsler grid, used since 1945, is a grid of horizontal and vertical lines used to monitor a person's central Visual field. The central black dot is used for fixation (a place for the eye to stare at). With normal vision, all lines surrounding the black dot will look straight and evenly spaced with no missing or odd looking areas when fixating on the grid's central black dot. When there is disease affecting the macula, as in macular degeneration, the lines can look bent, distorted and/or missing. See a VIDEO on HOW-TO-USE-AN-AMSLER-GRID Here: [1]

Macular degeneration by itself will not lead to total blindness. For that matter, only a very small number of people with visual impairment are totally blind. In almost all cases, some vision remains. Other complicating conditions may possibly lead to such an acute condition (severe stroke or trauma, untreated glaucoma, etc. ), but few macular degeneration patients experience total visual loss. ^[15] The area of the macula comprises about 5% of the retina and is responsible for about 35% of the visual field. The remaining 65% (the peripheral field) remains unaffected by the disease. ^[16]

The loss of central vision profoundly affects visual functioning. It is not possible, for example, to read without central vision. Pictures which attempt to depict the central visual loss of macular degeneration with a black spot do not really do justice to the devastating nature of the visual loss. This can be demonstrated by printing letters 6 inches high on a piece of paper and attempting to identify them while looking straight ahead and holding the paper slightly to the side. Most people find this surprisingly difficult to do.

Similar symptoms with a very different etiology and different treatment can be caused by Epiretinal membrane or macular puckeror leaking blood vessels in the eye. Epiretinal membrane is a disease of the eye in response to changes in the Vitreous humor or more rarely Diabetes. Epiretinal membrane is a disease of the eye in response to changes in the Vitreous humor or more rarely Diabetes. .

Diagnosis

Fluorescein angiography allows for the identification and localization of abnormal vascular processes. Fluorescein Angiography, or fluorescent angiography, is a technique for examining the circulation of the Retina using the Dye tracing Optical coherence tomography is now used by most ophthalmologists in the diagnosis and the followup evaluation of the response to treatment by using either Avastin or Lucentis which are injected into the vitreous of the eye at various intervals.

Prevention

The Age-Related Eye Disease Study showed that a combination of high-dose beta-carotene, vitamin C, vitamin E, and zinc can reduce the risk of developing advanced AMD by about 25 percent in those patients who have earlier but significant forms of the disease. The Age-Related Eye Disease Study was a Clinical trial sponsored by the National Eye Institute, one of the National Institutes of Health in the United Beta-carotene is an Organic compound - a Terpenoid, a red-orange pigment abundant in plants and fruits Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian See also Tocopherol, Tocotrienol Vitamin E is the collective name for a set of 8 related Tocopherols and Tocotrienols which are fat-soluble Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 This is the only proven intervention to decrease the risk of advanced AMD at this time. A follow up study, Age-Related Eye Disease Study 2 to study the potential benefits of lutein, zeaxanthine, and fish oil, is currently underway.

Anecortave acetate, (Retanne), is an anti-angiogenic drug that is given as an injection behind the eye (avoiding an injection directly into the eye) that is currently being studied as a potential way of reducing the risk of neovascular (or wet) AMD in high-risk patients.

Research started in 2005 has shown that intravitreal injection of Avastin (bevacizumab) can improve vision and slow down the macular degeneration. This therapy is currently being used in various centres around the world. Avastin is an immunoligic drug that prevents neovascularization. Hence it may also be effective in diabetic retinopathy. Avastin was initially used for the treatment of colorectal cancer.

A study by a neuroretinologist in the late 80's suggested that microcurrent stimulation of acupuncture points for the eye had positive effects in slowing and even stopping progression of the disease. This study was based on Ngok Cheng's research on the increased amounts of ATP levels in living tissue after being stimulated with microcurrent. ("The Effects of Electric Currents on ATP Generation, Protein Synthesis, and Membrane Transport in Rat Skin. ")^[17]

Recent studies suggest that statins, a family of drugs used for reducing cholesterol levels, may be effective in prevention of AMD, and in slowing its progression. The statins (or HMG-CoA reductase inhibitors) form a class of hypolipidemic drugs used to lower Cholesterol levels in people with or at risk of Cardiovascular Cholesterol is a Lipid found in the Cell membranes and transported in the Blood plasma of all Animals It is an essential component of mammalian ^[18]

Studies are underway at Harvard, with the goal of reducing lipofuscin accumulation. Lipofuscin is the name given to finely granular yellow brown Pigment granules composed of Lipid -containing residues of Lysosomal digestion ^[8]

On September 10, 2007, in a 6-year study, researchers, led by John Paul SanGiovanni of the National Eye Institute, Maryland found that Lutein and zeaxanthin (nutrients in eggs, spinach and other green vegetables) protect against blindness (macular degeneration), affecting 1. Research is defined as Human activity based on Intellectual application in the investigation of Matter. The National Eye Institute (NEI is one of the US National Institutes of Health that was established in 1968. As a pigment This Xanthophyll, like its sister compound Zeaxanthin, has primarily been used as a natural colorant due to its Orange-red Color Zeaxanthin is one of the two Carotenoids contained within the Retina of the Eye. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment Spinach ( Spinacia oleracea) is a Flowering plant in the family of Amaranthaceae. Green is a Color, the perception of which is evoked by light having a spectrum dominated by energy with a Wavelength of roughly 520–570- nm. The term " vegetable " generally means the edible parts of Plants The definition of the word is traditional rather than Scientific, however Blindness is the condition of lacking Visual perception due to Physiological or Neurological factors 2 million Americans, mostly after age 65. The United States of America —commonly referred to as the Lutein and zeaxanthin reduce the risk of AMD (journal Archives of Ophthalmology). A journal (through French from late Latin diurnalis, daily has several related meanings a daily record of events or business a private The Archives of Ophthalmology is a monthly professional Medical journal published by the American Medical Association. Foods considered good sources of the nutrients also include kale, turnip greens, collard greens, romaine lettuce, broccoli, zucchini, corn, garden peas and Brussels sprouts. Kale or Borecole is a form of Cabbage ( Brassica oleracea Acephala Group) green in color in which the central leaves do not For similar vegetables also called "turnip" see Turnip (disambiguation. Leaf vegetables, also called potherbs, greens, or leafy greens, are plant leaves eaten as a Vegetable, sometimes accompanied Collards, also called borekale (from the Dutch boerenkool (farmers' kale are various loose-leafed Cultivars of Brassica oleracea ( Acephala Romaine or cos lettuce ( Lactuca sativa L var longifolia) is a variety of Lettuce which grows in a long head of sturdy leaves with a firm rib Broccoli is a plant of the Cabbage family Brassicaceae (formerly Cruciferae Zucchini ( in North American and Australian English) or courgette (/kʊǝrˈʒɛt/ or in New Zealand and British English Maize (ˈmeɪz ( Zea mays L. ssp mays) known as corn in some countries is a cereal grain domesticated in Mesoamerica A garden is a planned space usually outdoors set aside for the display cultivation and enjoyment of Plants and other forms of Nature. A pea (inaccurately called a '''sweet pea''' by food distubutors is most commonly the small spherical Seed or the seed-pod of the Legume Pisum This article is about the plant For the pencil game see Sprouts (game. ^[19]

Juvenile macular degeneration

Juvenile macular degeneration is not a term in standard usage at this time. The preferred term for conditions that affect the macula in younger individuals related to genetics is macular dystrophy. Examples of these include:

• Best's disease
• Doyne's honeycomb retinal dystrophy
• Sorsby's disease
• Stargardt's disease

The first genetic link to juvenile macular degeneration was discovered at the Cleveland Clinic. Vitelliform macular dystrophy or vitelliform dystrophy is a genetic Eye disorder that can cause progressive Vision loss. The Cleveland Clinic (formally known as the Cleveland Clinic Foundation) is a multispecialty academic medical center located in Cleveland, Ohio,

Impact

Macular degeneration, in its advanced forms, can result in legal blindness, resulting in a loss of driving privileges and an inability to read all but very large type. Blindness is the condition of lacking Visual perception due to Physiological or Neurological factors Perhaps the most grievous loss is the inability to see faces clearly or at all.

Some of these losses can be offset by the use of adaptive devices. A closed-circuit television reader can make reading possible, and specialized screen-reading computer software, e. g. , JAWS for Windows, can give the blind person access to word processing, spreadsheet, financial, and e-mail programs. JAWS (an acronym for Job Access With Speech) is a Screen reader, a software program for visually impaired users produced by the Blind and Low Vision Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft.

References

External links

• Macular degeneration at the Open Directory Project
• 'Robo' Gene Fights Macular Degeneration

The Open Directory Project ( ODP) also known as dmoz (from directory

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