Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of vision loss in people over age 65. Although it rarely causes total blindness, it can cause permanent loss of your central vision making it difficult to see near and far. Before understanding how AMD affects your vision, it is first important to understand how an eye normally sees.

How we see?

Light passes through the pupil and the lens. The cornea and the lens focus the light onto the retina in the back of the eye. The retina takes the light rays and sends signals through the optic nerve to the brain, where they are recognized as images.

The retina is divided into two areas: the macula and the peripheral retina. Although the macula is the small area in the center of the retina, it is much more sensitive to detail than the peripheral retina. The macula is what allows you to focus on fine details clearly. The peripheral retina is what gives your side vision.

Macular degeneration is one cause for deterioration of the macula. When the macula doesn’t function correctly, central vision may be affected distorted, dim or blurred.

Facts about AMD

  • Most people with AMD are over the age of 50.
  • It is hereditary.
  • It is less common among African-Americans.
  • Smokers have a higher risk of developing AMD.
  • It is not fully known why AMD develops although it is likely due to cell damage in the natural aging process.
  • The progression of AMD may be slowed by using a specific formula of vitamins.
  • ‘Wet’ macular degeneration may be treated with injections or laser.

How does AMD Develop?

The retina is made of many layers sandwiched together into a smooth surface, which work together to allow you to see clearly. When the layer under the retina is disrupted by tiny deposits called drusen, or by other age-related changes, AMD could develop. Only a few people with drusen will develop severe AMD with vision loss.

Symptoms of AMD

While there are some symptoms of AMD, most people do not realize they have macular degeneration until vision problems are noticeable or it is detected during an eye exam. During its earliest stages, symptoms of AMD include:

  • Blurred distance vision
  • Blurred reading vision
  • Distorted vision
  • Dark or blank spots in the central vision
  • Colors do not look the same in both eyes

Types of AMD

There are two different types of AMD:  “Dry” AMD and “Wet” AMD. Dry AMD is the most common form of AMD, and is usually caused by the thinning of the macula tissues. Wet AMD occurs in about 10% of all AMD cases, but can cause more damage to the central vision than dry AMD. It is named for the abnormal blood vessels that develop underneath the retina, which can leak fluid or blood.  Vision loss may occur much faster and be more noticeable in “wet” AMD compared to “dry” AMD.  Both forms can exist simultaneously and it is possible for an eye to convert from “dry” to “wet”.  This conversion may present with a change in vision or new distortion best seen on an Amsler grid test card.

Illustration of "dry" AMD
Illustration of "wet" AMD

How is AMD diagnosed?

Some people don’t realize they have macular degeneration until vision problems are noticeable. Regular eye exams help detect problems before you may even be aware of them.  Trained retinal specialists can diagnose AMD by looking into the eye with a special microscope.

Depending on the type of AMD suspected, fluroescein angiography may be used to capture detailed photographs of the blood vessels in your eyes. A special non-iodine based dye is injected into a vein in your arm and a series of photographs are taken as the dye flows through the vessels in the eyes. Any abnormal vessels will be highlighted by the dye helping to guide the selection of treatment options.  Optical Coherence Tomography is another highly sensitive test that is routinely used to help diagnose AMD and guide treatment.  It is easily obtained in the office and generates a ‘cross-sectional’ scan of the macula.  It is very similar to a X-ray, except light is used to create the image instead of radiation.

How can I monitor AMD?

If you have been diagnosed with the dry form of AMD, you can use a chart called an Amsler grid to monitor your vision every day. This simple vision test will help you notice any changes in your vision that may be a sign that your AMD is progressing into the wet form. This is an easy test, where you will look at a chart resembling graph paper. Covering one eye at a time, you will look directly at the center of the grid and observe the pattern of the vertical and horizontal lines on the grid. This will help you look for any visual abnormalities, including distortion, blurriness and darkness.

Amsler grid
What treatments are available for AMD?

Unfortunately, as of today, there is no treatment available that has proven to be effective in treating the dry form of AMD; however, a specific formulation of antioxidant vitamins and zinc (known as AREDS vitamins
mg vitamin C, 400 IU vitamin E, 15mg beta-carotene) and 80 mg of zinc (2 mg of copper)) may help to reduce the impact of AMD by slowing the progression of the disease in some people.  The AREDS vitamins were shown to reduce the risk of progression to advanced AMD in a  major clinical trial known as the Age-Related Eye Disease Study.  AREDS vitamins can be obtained over the counter.  Smokers should use a formulation without beta carotene.  There has been recent suggestion that omega-3 long-chain polyunsaturated fatty acid may also decrease the risk of advanced AMD.  The effectivity of omega-3, lutein, and zeaxanthin is currently being evaluated in the AREDS II trial which began in the Summer of 2006. Patients already using dietary supplements are advised to seek assistance from their primary care physician before beginning new therapies. 

Thermal laser treatment, photodynamic therapy and/or anti-VEGF (vascular endothelial growth factor)  injections may be used to treat wet AMD. Although these treatments can reduce the risk of severe vision loss, they do not completely eliminate the risk. Your retina specialist will work with you individually to determine what treatment will work best for your individual case. 

What if my AMD cannot be treated?

Only about 10% of all AMD cases are the wet form for which laser or injections would be appropriate.  Most are treatable.  In some significant scarring from the abnormal vessels will limit visual potential.  People who have untreatable wet or dry AMD usually do not become completely blind because the peripheral vision is not typically affected.  Furthermore, with some rehabilitation and special devices, others can learn to use the vision they do have.

Low-vision aids are also available to assist people with untreatable AMD. These specially designed devices can include:

  • Magnifying spectacles
  • Telescopes
  • Hand magnifiers
  • Stand magnifiers
  • Video magnifiers

There are other low-vision techniques that can help people adjust and make everyday activities easier, including:

  • Large print books
  • Computer magnification technology
  • Sitting closer to the television
  • Using bold-tipped markers
  • Using bright lights while reading
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