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  Retina > Age Related Macular Degeneration  
  What is the retina?  
     
 
The retina is the back surface inside the eyeball, opposite the lens. It contains millions of light sensitive photoreceptor cells, called rods and cones. An image projected by the lens onto the retina is sensed by the rods and cones as different intensities of light and different colors. When light hits rods or cones, a biochemical reaction occurs, which initiates the transmission of signals along nerve cells to the brain, with information about light, color and position in the retina. In the brain, the signals from throughout the retina are assembled into the experience of seeing what is before us.
  
     
  What is the macula?  
  The central portion of the retina directly opposite the lens, is called the macula. It is rich in cones, the cells which enable us to see fine detail and color. There are three classes of cones, each most sensitive to a different color: red, green or blue.  
  What is the fovea?  
  At the center of the macula is very small area called the fovea. Cones are most concentrated in the fovea. Despite its small size, relative to the rest of the retina, the fovea is very important for our ability to see fine detail and color.  
  What is Macular Degeneration?    
 
Macular Degeneration is a blinding disease which causes the death of cells in the light-sensitive portion of the eye called the retina. These cells, called photoreceptor cells, are most severely affected in a specialized region of the retina called the macula, thus the name Macular Degeneration. The macula is responsible for what is called "fine acuity vision"; this is the vision that you use when driving, reading, sewing, watching television or any activity that requires one to focus on very small objects. Loss of the light-sensitive cells in the macula has devastating effects on vision and can lead to total blindness.
 
  What is the difference between the "wet" and "dry" forms of ARMD?  
 
The "dry" form of ARMD refers to the atrophic form which is characterized, in its late stages, by the degeneration (i.e. atrophy) of the retina in a region that includes the macula. "Dry" ARMD develops and progresses slowly over a period of 5-10 years or longer. Approximately 85% of the total ARMD patient population has this atrophic form. The less prevalent, "wet" type of ARMD is also referred to as neovascular or exudative ARMD. It is characterized by the ingrowth of new blood vessels from the choroid. "Wet" ARMD progresses much more rapidly, over a period of weeks or months, and usually results in legal blindness in the central portion of the visual field.
  
     
  If I develop "wet" or "dry" ARMD in one eye, will it eventually affect the opposite eye?  
  Probably. The fellow eye is at high risk of following suit, but the timing can vary significantly from person to person.  
     
  What are the risk factors associated with ARMD?  
 

The strongest risk factors are:

 
     
 
  1. Age. The incidence of all forms of ARMD rises steeply with advancing age. In one large study, ARMD increased from approximately 4% of individuals at 43 to 54 years of age, to 23% in those 75 years or older.
  2. Drusen. The presence of numerous and/or large drusen, accompanied by specific pigmentary changes in the macula, is considered to be diagnostic of early atrophic ARMD.
  3. Smoking. The incidence of both "wet" and "dry" ARMD is strongly correlated a history of smoking, and the degree of risk is proportional to the amount of cigarette consumption.
  4. Genetic factors. Several studies have demonstrated a high rate of concordance in the development of ARMD among twins, particularly among identical twins. In family-based studies, the likelihood of developing ARMD is nearly 20 times higher if one or both parents have ARMD. It is highly likely that one or more gene alterations carried by the affected individual increase the susceptibility in his/her offspring.
 
  How does diet influence macular degeneration?  
     
  Several studies now indicate that diets rich in green leafy vegetables, such as spinach, chard and mustard greens, can reduce the risk of ARMD. These and other vegetables are rich in certain pigments known as carotenoids. Among these, lutein and zeaxanthin are two that are highly concentrated in the macula where they may have effects that protect RPE and/or retinal cells from injury caused by the formation of peroxides and other toxic byproducts of the visual cycle. Lutein and zeaxanthin are now widely available as dietary supplements; however, their efficacy when consumed in this form has not been well studied.  
  Have vitamins and other nutritional supplements been shown to be effective as treatments for ARMD?  
     
  There have been at least five published trials that have tried to determine whether dietary supplements, such as vitamins A, C, E or zinc can arrest or prevent the development of ARMD. Thus far, the results from these small scale studies have not been encouraging. However, new data from a much larger study called the Age-Related Eye Disease Study (AREDS) indicates that dietary supplementation with 500 mg of vitamin C, 400 IU of vitamin E, 15 milligrams of beta-carotene and 80 milligrams of zinc (as zinc oxide) can reduce the risk of developing advanced ARMD by approximately 25%.  
     
  What are the Symptoms of ARMD?  
  Macular degeneration develops differently in each person. Though it is more common to develop in people over 60, depending upon risk factors, it may develop much earlier. Because it will affect different regions of the macula from person to person, the symptoms tend to vary. In general, the following symptoms are indicative of macular degeneration:  
     
 
  • The loss of the ability to see objects clearly.
  • Vision that is noticeably distorted.
  • Straight lines appear wavy.
  • Objects may appear as the wrong shape or size.
  • The loss of clear, correct colors.
  • Blurry or a dark, empty area in the center of vision.
    If you experience any of these symptoms in either one or both eyes, schedule an
    appointment with your ophthalmologist for an examination immediately.
  
  What is an Amsler Grid?  
     
  Early detection of changes in the central sight area is vital to safeguarding vision from needless loss due to macular degeneration and diabetic retinopathy. If you are at risk for developing macular degeneration or have diabetes, it is wise to check the vision in each eye each day. Early detection of a problem with vision increases the chance of saving eyesight through timely laser treatment.  
   
 

Amsler Grid

Simulated "Blurred Waves" on Amsler Grid (note distortion and gray shaded area)

  
     
  A simple test of vision quality that detects even minor changes when they first occur is the use of the Amsler Grid. The Amsler Grid is a chart that can reveal signs of wet macular degeneration. You can get one from your ophthalmologist and test your vision at home. This easy test only takes a moment for each eye. The results can give you timely warning of changes in your retina that warrant immediate attention by an ophthalmologist.
  
     
  Instructions for using Amsler Grid at home:
  
     
 
  1. .Wear your reading glasses
  2. Hold the Amsler grid at a normal reading distance
  3. Cover one eye
  4. Look at the dot in the center of the grid
  5. Note how the lines and squares appear.
  6. Test the other eye in the same manner
  
  All of the lines should be straight and the squares of a uniform size. If you note any changes in the appearance of the grid, such as distortion, blurring, discoloration, dark or missing areas of the grid, or any other changes, call and see your eye doctor immediately. Do not wait to see if the changes will clear on their own. Timely treatment is vital to safeguarding your vision.
  
     
  If a diagnosis for wet macular degeneration is made by your ophthalmologist, you should
use the grid on a daily basis to check for changes in your vision.		  
     
  What are the Treatments for Macular Degeneration?  
     
  Aside from cessation of smoking and a healthy diet of dark green leafy vegetables and fruits supplemented by zinc and anti-oxidant vitamins (Vitamins E, C, and beta carotene), very little is available to help patients with atrophic or "dry" AMD to prevent progression to more serious stages of debilitating disease.  
     
  For wet ARMD, essentially, persons have, at present, three possible treatment options:  thermal (heat laser); Photodynamic Therapy; or anti-VEFG drugs.  
     
  1. Laser Photocoagulation  
     
  Laser photocoagulation is a surgical procedure involving the application of a hot laser to seal and halt or slow the progression of abnormal blood vessels. In the 1990’s laser treatment was the only therapy available for AMD.  
     
  Through the use of a high-energy light that turns to heat when it hits the parts of the retina to be treated, laser photocoagulation seals the choroidal neovascularization (CNV) and inhibits the leaky blood vessels growth, preventing further vision deterioration. A scar forms as a result of the treatment, and this scar creates a permanent blind spot in the field of vision. Vision does not usually improve after laser treatment and may even be somewhat worse. However, loss of vision following laser treatment, though immediate, is generally less severe than the eventual loss of vision that usually occurs if laser treatment is not done. In many cases, some visual distortion will disappear after laser treatment .  
     
  2. Photo Dynamic Therapy (PDT)  
     
  Photodynamic Therapy (PDT) (trade name Visudyne) uses a non-thermal (or cold) laser with an intravenous light-sensitive drug to seal and halt or slow the progression of abnormal retina blood vessels. This treatment does not produce a blind spot on the retina. The light is shone directly at the targeted tissue and the drug accumulates in these cells. It therefore reduces damage to normal surrounding tissue and allows the treatment to be given again as needed.   
     
  However, early diagnosis of AMD is key, because once vision is lost due to of the growth of abnormal blood vessels, it cannot be reclaimed by either treatment.  
     
  3. Anti-angiogenesis Therapies  
  As of February 2006, pegaptanib sodium (trade name Macugen) is approved for use in Canada, the United States and Europe.  Other investigations are also showing promise, including combination therapies, which combine traditional PDT therapy with new drugs like intravitreal steroids(triamcinolone acetonide), Avastin, etc to increase the effectiveness of PDT.  
     
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