Human eye cross-sectional view. Courtesy NIH National Eye InstituteNormal vision. Courtesy NIH National Eye InstituteThe same view with age-related macular deneneration.
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Macular degeneration

Macular degeneration is a medical condition where the light sensing cells in the macula malfunction and over time cease to work. 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. There are two basic types of the disease: Standard Macular Degeneration (MD) and Age Related Macular Degeneration (ARMD), with ARMD being the most common form of the condition. Macular degeneration that is not age related is most commonly caused by an inherited condition. These forms are sometimes called Juvenile macular degeneration (JMD). more...

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In macular degeneration the final form results in missing or blurred vision in the central, reading part of vision. The outer, peripheral part of the vision remains intact.

Age related macular degeneration

ARMD is further divided into a "dry," or nonexudative, form and a "wet," or exudative, form. Eighty five to ninety percent of cases are categorized as "dry" macular degeneration where fatty tissue, known as drusen, will slowly build up behind the retina. Ten to fifteen percent of cases involve the growth of abnormal blood vessels under the retina. These cases are called "wet" macular degeneration due to the leakage of blood and other fluid from behind the retina into the eye. Wet macular degeneration usually begins as the dry form. If allowed to continue without treatment it will completely destroy the macula. Medical, photodynamic, laser photocoagulation and laser treatment of wet macular degeneration are available.

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.
  • Smoking: The only environmental exposure clearly associated with macular degeneration is tobacco smoking .
  • 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 four fold higher risk.
  • Macular Degeneration Gene: Complement factor H (CFH) gene has been determined to be strongly associated with a person's risk for developing macular degeneration.
  • Exposure to sunlight especially blue light.
  • Hypertension.
  • Cardiovascular Risk Factors - high cholesterol, obesity.
  • High fat intake is associated with an increased risk of macular degeneration in both women and men. Fat provides about 42 % of the calories in the average American diet. A diet that derives closer to 20-25 % of total calories from fat is probably healthier. Reducing fat intake to this level means cutting down greatly on consumption of red meats and dairy products such as milk, cheese, and butter. Eating more cold-water fish (at least twice weekly), rather than red meats and eating any type of nuts may help macular degeneration patients.(Reference: Macular degeneration Types and Risk Factors.
  • 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 (RPE) may be partly responsible for decreasing the digestive rate of photoreceptor outer rod segments (POS) by the RPE. A decrease in the digestive rate of POS has been shown to be associated with lipofuscin formation - a classic symptom of macular degeneration. (Reference: Ophthalmic Research, 2005; volume 37: pages 136-141. "Melanin aggregation and polymerization: possible implications in age related macular degeneration")
  • Race Macular degeneration is more likely to be found in whites than in blacks.

Read more at Wikipedia.org


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New drug treats age-related macular degeneration
From FDA Consumer, 3/1/05

A new therapy to slow vision loss in people with wet age-related macular degeneration (AMD), an eye disease that destroys central vision, has been approved by the FDA.

Macugen (pegaptanib sodium injection) is the first in a new class of ophthalmic drugs to specifically target vascular endothelial growth factor (VEGF), a protein that acts as a signal in triggering the abnormal blood vessel growth and leakage that is the hallmark of wet AMD.

AMD is the leading cause of irreversible blindness in patients older than 50 in developed countries. According to a study in the April 2004 issue of Archives of Ophthalmology, AMD is the leading cause of blindness for white Americans, with 1.8 million cases reported in 2002.

The disease occurs in two forms: wet and dry. Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula--located in the center of the retina. These new blood vessels tend to be fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye, causing rapid damage to occur. An early symptom of wet AMD is straight lines that appear wavy.

Dry AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. The most common symptom of this type is slightly blurred vision. Wet AMD, which makes up about 10 percent of AMD cases, is considered to be more severe than the dry form.

Approved for marketing in December 2004, Macugen is a single strand of nucleic acid that specifically binds to a particular protein that plays a critical role in the formation of new blood vessels and increased leakage from blood vessels--two of the primary pathological processes responsible for the vision loss associated with wet AMD.

Macugen therapy was co-developed by Eyetech Pharmaceuticals Inc. and Pfizer Inc., both of New York City.

COPYRIGHT 2005 U.S. Government Printing Office
COPYRIGHT 2005 Gale Group

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