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Age-related macular degeneration AMD

Age-related macular degeneration (AMD) is a disease that blurs the sharp, central vision
you need for "straight-ahead" activities such as reading, sewing, and driving. AMD affects
the macula, the part of the eye that allows you to see fine detail.  AMD causes no pain.

In some cases, AMD advances so slowly that people notice little change in their vision.
In others, the disease progresses faster and may lead to a loss of vision in both eyes.

Where is the macula?

The macula is located in the centre of the retina , the light-sensitive tissue at the back
of the eye. The retina instantly converts light, or an image, into electrical impulses. The
retina then sends these impulses, or nerve signals, to the brain.

Are there different forms of AMD?

AMD occurs in two forms: wet and dry.

Wet AMD

Wet AMD occurs when abnormal blood vessels behind the retina start to grow under
the macula. These new blood vessels tend to be very fragile and often leak blood and
fluid. The blood and fluid raise the macula from its normal place at the back of the eye.
Damage to the macula occurs rapidly.

With wet AMD , loss of central vision can occur quickly. Wet AMD is considered to be
advanced AMD and is more severe than the dry form.

An early symptom of wet AMD is that straight lines appear wavy. If you notice this
condition or other changes to your vision, contact your eye care professional at once.
You need a comprehensive dilated eye exam.

Dry AMD

Dry AMD occurs when the light-sensitive cells in the macula slowly break down,
gradually blurring central vision in the affected eye. As dry AMD gets worse, you
may see a blurred spot in the centre of your vision. Over time, as less of the
macula functions, central vision in the affected eye can be lost gradually.

The most common symptom of dry AMD is slightly blurred vision. You may have
difficulty recognizing faces. You may need more light for reading and other tasks.
Dry AMD generally affects both eyes, but vision can be lost in one eye while the
other eye seems unaffected.

One of the most common early signs of dry AMD is drusen. Drusen are yellow
deposits under the retina. They often are found in people over age 60. Your eye
care professional can detect drusen during a comprehensive dilated eye exam.

Dry AMD has three stages, all of which may occur in one or both eyes:

1. Early AMD . People with early AMD have either several small drusen or
   a few medium-sized drusen. At this stage, there are no symptoms and no
   vision loss.
    
2. Intermediate AMD . People with intermediate AMD have either many
   medium-sized drusen or one or more large drusen. Some people see
   a blurred spot in the centre of their vision. More light may be needed
   for reading and other tasks.
    
3. Advanced Dry AMD. In addition to drusen, people with advanced dry AMD
   have a breakdown of light-sensitive cells and supporting tissue in the central
   retinal area. This breakdown can cause a blurred spot in the centre of your
   vision. Over time, the blurred spot may get bigger and darker, taking more
   of your central vision. You may have difficulty reading or recognizing faces
   until they are very close to you.

If you have vision loss from dry AMD in one eye only, you may not notice any
changes in your overall vision. With the other eye seeing clearly, you still can
drive, read, and see fine details. You may notice changes in your vision only if
AMD affects both eyes. If blurriness occurs in your vision, see an eye care
professional for a comprehensive dilated eye exam.

The dry form is much more common. More than 85 percent of all people with intermediate
and advanced AMD combined have the dry form.

However, if only advanced AMD is considered, about two-thirds of patients have the wet form.
Because almost all vision loss comes from advanced AMD , the wet form leads to significantly
more vision loss than the dry form .

All people who have the wet form had the dry form first.

The dry form can advance and cause vision loss without turning into the wet form . The dry
form also can suddenly turn into the wet form , even during early stage AMD . There is no
way to tell if or when the dry form will turn into the wet form .

Risk factors for AMD

AMD can occur during middle age. The risk increases with aging. Other risk factors include:

• Smoking.
• Obesity. Research studies suggest a link between obesity and the progression of early
  and intermediate stage AMD to advanced AMD.
• Race. Whites are much more likely to lose vision from AMD than African Americans.
• Family history. People with a family history of AMD are at higher risk of getting the
  disease.
• Gender. Women appear to be at greater risk than men.

Diagnosis of AMD

AMD is detected during a comprehensive eye exam that includes:

• Visual acuity test. This eye chart test measures how well you see at various distances.
• Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your
  eye care professional uses a special magnifying lens to examine your retina and optic
  nerve for signs of AMD and other eye problems. After the exam, your close-up vision
  may remain blurred for several hours.
• Tonometry. An instrument measures the pressure inside the eye. Numbing drops may
  be applied to your eye for this test.

Your eye care professional also may do other tests to learn more about the structure and
health of your eye.

If your eye care professional believes you need treatment for wet AMD , he or she may
suggest a fluorescein angiogram. In this test, a special dye is injected into your arm. Pictures
are taken as the dye passes through the blood vessels in your retina. The test allows your
eye care professional to identify any leaking blood vessels and recommend treatment.

Treatment of AMD

Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss.
However, treatment can delay and possibly prevent intermediate AMD from progressing to
the advanced stage, in which vision loss occurs.

Wet AMD treatment

There are two treatments for wet AMD: laser surgery and photodynamic therapy. Neither
treatment is a cure for wet AMD. Each treatment may slow the rate of vision decline or stop
further vision loss. The disease and loss of vision may progress despite treatment.

• Laser surgery. This procedure uses a laser to destroy the fragile, leaky blood vessels.
  A high energy beam of light is aimed directly onto the new blood vessels and destroys
  them, preventing further loss of vision. However, laser treatment also may destroy
  some surrounding healthy tissue and some vision. Only a small percentage of people
  with wet AMD can be treated with laser surgery. Laser surgery is more effective if the
  leaky blood vessels have developed away from the fovea , the central part of the
  macula. Laser surgery is performed in a doctor's office or eye clinic.

  The risk of new blood vessels developing after laser treatment is high. Repeated
  treatments may be necessary. In some cases, vision loss may progress despite
  repeated treatments.

• Photodynamic therapy. A drug is injected into your arm. It travels throughout the
  body, including the new blood vessels in your eye. The drug tends to "stick" to the
  surface of new blood vessels. Next, a light is shined into your eye for about 90 seconds.
  The light activates the drug. The activated drug destroys the new blood vessels and
  leads to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy
  surrounding healthy tissue. Because the drug is activated by light, you must avoid
  exposing your skin or eyes to direct sunlight or bright indoor light for five days after
  treatment. Photodynamic therapy is relatively painless. It takes about 20 minutes
  and can be performed in a doctor's office.

  Photodynamic therapy slows the rate of vision loss. It does not stop vision loss or
  restore vision in eyes already damaged by advanced AMD . Treatment results often
  are temporary. You may need to be treated again.

What can I do to protect my vision?

• Dry AMD . If you have dry AMD , you should have a comprehensive dilated eye exam
  at least once a year. Your eye care professional can monitor your condition and check
  for other eye diseases. Also, if you have intermediate AMD in one or both eyes, or
  advanced AMD in one eye only, your doctor may suggest that you take the AREDS
  formulation containing the high levels of antioxidants and zinc.

  Because dry AMD can turn into wet AMD at any time, you should get an Amsler grid
  from your eye care professional. Use the grid every day to evaluate your vision for
  signs of wet AMD . This quick test works best for people who still have good central
  vision. Check each eye separately. Cover one eye and look at the grid. Then cover
  your other eye and look at the grid. If you detect any changes in the appearance of
  this grid or in your everyday vision while reading the newspaper or watching television,
  get a comprehensive dilated eye exam.

• Wet AMD . If you have wet AMD and your doctor advises treatment, do not wait. After
  laser surgery or photodynamic therapy, you will need frequent eye exams to detect
  any recurrence of leaking blood vessels. Studies show that people who smoke have
  a greater risk of recurrence than those who don't. In addition, check your vision at
  home with the Amsler grid.

If you detect any changes, schedule an eye exam immediately.

Below is an example of Amsler Grid test on a patient with Age-related Macular
Degeneration.

Click here to find out more about Amsler grid test.