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Age Related Macular Degeneration

Age Related Macular Degeneration
 

Macular Pigment Research Group (MPRG) publication

 
   
Macular

What is the macula?
The macula is located at the centre of the back of the eye. It is a small and highly sensitive part of the eye responsible for colour vision and detailed central vision. The macula allows us to appreciate detail and perform tasks that require good central vision such as reading, watching television, and recognising faces.

What is AMD?
Age-related macular degeneration (AMD), as its name suggests, occurs with increasing age and results in degeneration of the macula. AMD is the leading cause of irreversible blindness in people over 50 years of age, affecting an estimated 13 million sufferers across Europe. AMD is particularly frustrating because it results in a loss of central vision. In other words, someone with AMD cannot see what they are looking directly at, and are therefore unable to read, watch TV, recognise familiar faces, or drive. The number of people affected by AMD is increasing, largely because we are all living longer.

AMD occurs in two forms, the early form and the late form.

With early ADM, the degeneration of the retina is associated with the formation of small yellow deposits (called drusen) and pigmentary changes at the macula. Central vision is typically unaffected in this early stage.

With advanced AMD, loss of central vision occurs. Advanced AMD can be wet (i.e. neovascular) or dry (i.e. atrophic). Loss of central vision is more rapid with the wet form of advanced AMD than with the atrophic form. In the wet form, abnormal blood vessels grow at the back of the eye. These blood vessels bleed and leak fluid, thus distorting or destroying central vision, and ultimately causing scar formation at the macula.

Normal Vision and Age-related macular degeneration
                           Normal Vision                                        Age-related macular degeneration

What causes AMD?
Although the exact cause of AMD is unknown, it is believed that damage by free radicals within the eye is important. Free radicals are unstable substances that are produced in response to the use of oxygen, and in response to blue light entering the eye. Because we use oxygen to live, and because we are constantly exposed to blue light, damage caused by free radicals is simply unavoidable.

What are the symptoms of AMD?
The main symptom of AMD is dim or fuzzy central vision, which can affect a person’s ability to perform fine-detail visual tasks, such as reading. Objects may appear distorted or smaller than they really are. Faces will become more difficult to recognise. As the disease progresses, blind spots may develop, reducing central vision further. However, good peripheral (side) vision for orientation is unaffected.

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 at various distances.
  • Pupil dilation and fundus examination: The pupil is widened with eye drops to allow a close-up examination of the retina at the back of the eye.
  • 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 through the blood vessels in the retina, helping the physician evaluate if the vessels are leaking and whether or not the leaking can be treated.
  • Amsler grid: Used to detect wet AMD, this diagnostic test uses a grid pattern to determine if the straight lines in the pattern appear wavy or missing to the patient, either of which may signal the development of the wet AMD.
How to use the Amsler grid:
Amsler Grid

1. Hold the grid:

  • In the well-lit room
  • About 30-40cm away from your face
  • Wearing your reading glasses if you require them

2. Cover one eye and focus on the central dot

3. Check for any irregularities within the grid, e.g. distortion, wavy lines, different sized or missing squares

4. Test each eye separately


 

If you notice any irregularities, make an appointment to see your eyecare professional immediately

 

Is there any treatment for AMD?
Early AMD: There is no cure or treatment for early AMD at present. However, studies have shown that for some people who already have moderate to severe early AMD, taking certain vitamins and minerals may reduce the chance of getting the advanced form of AMD. If you have early AMD, you should carefully monitor your vision for any changes, and see your doctor for frequent check-ups. The MPRG suggests that having your macular pigment measured may also be useful, as it may identify the need to take appropriate supplements which may, in turn, prevent disease progression to the advanced form of AMD.

Advanced AMD: Wet AMD can often be treated with laser surgery, photodynamic therapy (PDT), or injections into the eye. Treatment will generally not restore central vision, but it may slow down, or prevent further visual loss. Unfortunately, there is no known treatment for the dry form of advanced AMD.

 

What are lutein, zeaxanthin, and meso-zeaxanthin?
Lutein and zeaxanthin are dietary carotenoids. Carotenoids are coloured pigments which are predominantly found is fruits and vegetables such as grapes, spinach, sweetcorn and most leafy greens. Egg yolks are also very good source of lutein and zeaxanthin. Meso-zeaxanthin is the third component of the macular pigment, and is only found at the centre of the macula, where vision is sharpest. Meso-zeaxanthin is formed by the conversion of lutein to meso-zeaxanthin at the macula.

Why is macular pigment important?
Macular pigment is yellow in colour, and therefore absorbs damaging blue light. Also, macular pigment is a powerful neutraliser of the radicals. The MPRG believe that macular pigment protects the macula from the aging process i.e. AMD. The MPRG has shown that people who are at a high risk of developing AMD have a lack of this pigment in their eye.