When reading, recognizing faces become difficult

Watch out for Age-related Macular Degeneration (AMD)

By Dr D. H. H. Wariyapola

Age-related macular degeneration (AMD) is a disease that affects an individual's central vision. AMD is the most common cause of severe vision loss among people over 60. Because only the centre of vision is affected, people rarely go blind from this disease. However, AMD can make it difficult to read, drive, or perform other daily activities that require fine, central vision.

AMD occurs when the macula, which is located in the centre of the retina and provides us with sight in the centre of our field of vision, begins to degenerate. With less of the macula working, central vision - which is necessary for driving, reading, recognizing faces, and performing close-up work - begins to deteriorate.

What are the different types of AMD?

There are two primary types of AMD:

• Dry AMD
  This type of AMD is the most common. While its cause is unknown, it occurs as the light sensitive cells in the macula slowly deteriorate, generally occurring in one eye at a time.
• Wet AMD
  This type of AMD is less common, but accounts for almost all severe vision loss caused by either type of AMD. Wet AMD occurs when new blood vessels behind the retina start to grow beneath the retina where they leak fluid and blood and can create a large blind spot in the centre of the visual field. If this happens, there is a marked disturbance of vision in a short period of time.
  What are the symptoms of AMD?
  The following are the most common symptoms of AMD. However, each individual may experience symptoms differently. Symptoms may include:
• blurry or fuzzy vision
• difficulty recognizing familiar faces
• straight lines, such as sentences on a page, telephone poles, and the sides of buildings, appear wavy
• a dark or empty area (blind spot) appears in the centre of vision
• rapid loss of central vision - vision necessary for driving, reading, recognizing faces, and performing close-up work.
  The presence of drusen, tiny yellow deposits in the retina, is one of the most common early signs of AMD. These will be visible to your physician during an eye examination. While the presence of drusen alone does not indicate the disease, it may mean the eye is at risk for developing more severe AMD.

The symptoms of AMD may resemble other eye conditions. Consult your ophthalmologist for diagnosis.

How is AMD diagnosed?

In addition to a complete medical history and eye examination, your eye care professional may perform the following tests to diagnose AMD:

• visual acuity test - the common eye chart test which measures vision ability at various distances.
• pupil dilation - the pupil is widened with eye drops to allow a close-up examination of the eye's retina.
• Amsler grid - used to detect wet AMD, this diagnostic test uses a checkerboard-like grid (reduced size shown here; normal vision on the left and vision with AMD on the right) to determine if the straight lines in the pattern appear wavy or missing to the patient - both indications may signal the possibility of AMD.
• Fluorescein angiography - used to detect wet AMD, this diagnostic test involves a special dye injected into a vein in the arm. Pictures are then taken as the dye passes through the blood vessels in the retina, helping the physician evaluate if the blood vessels are leaking and whether or not the leaking can be treated.

What is a risk factor?

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.

Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors.

But, knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviours and being clinically monitored for the disease.

What are the risk factors for AMD?

• Gender
  According to some studies, women are at greater risk than men.
• Age
  Although AMD can occur during middle age, the risk for developing the disease increases as a person ages. Studies have shown that while persons in their 50s have only a two percent risk of developing AMD, that rises to nearly 30 percent in persons over 75.
• Smoking
  Recent studies have shown that smoking is a major risk factor for age-related macular degeneration.
• Family history
  Persons with a family history of AMD may have a higher risk of developing AMD.
• Hypertension and cardiovascular disease
• Obesity
  Studies have indicated that obesity may be linked to the progression of AMD.
• High blood cholesterol levels
  Persons with elevated blood cholesterol levels may be at higher risk for wet AMD.

Treatment for AMD:

Two approved treatments are available to slow the rate of vision decline or to stop further vision loss due to wet age-related macular degeneration (AMD).

Laser Photocoagulation

Until recently, the only available treatment for wet age-related macular degeneration was laser photocoagulation, which is appropriate for the 10%-20% of patients whose lesions are small, well-defined, and located ideally outside the macula. However, because this treatment also destroys part of the overlying retina and its light-sensitive cells, it can cause some immediate and permanent vision loss. In addition, 50% of patients treated in this way suffer from recurrences that require re-treatment.

Photo Dynamic Therapy

Photo Dynamic therapy is the first and only drug therapy approved by the US Food and Drug Administration for the treatment of age-related macular degeneration. PDT can slow or even halt vision loss related to classic wet age-related macular degeneration. (Your doctor may call this type of degeneration predominantly classic subfoveal choroidal neovascularization.)

The most common side effects were injection site reactions (extravasation [some of the drug may leak from the vein] and rashes), blurred vision, decreased visual acuity, and visual field defects.

Infusion induces temporary photosensitivity. Thus exposure of skin and eyes to direct sunlight or bright indoor light should be avoided for 2 days.

LUCENTIS™ (ranibizumab injection)

LUCENTIS™ (ranibizumab injection) is a prescription medicine for the treatment of patients with wet age-related macular degeneration .

LUCENTIS™ is a breakthrough treatment for wet AMD that can do more than just help you maintain your vision. With LUCENTIS™, people with wet AMD may see their vision improve or keep the vision they have.

Currently, there is no treatment for dry AMD. This does not, however, indicate that sight will automatically be lost, particularly if the AMD affects only one eye. Central vision may eventually be lost or diminished, but generally the rate of loss is slow.

The writer is Consultant Eye Surgeon , Sri Jayewardenepura General Hospital