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AGE-RELATED MACULAR DEGENERATION (AMD)

AGE-RELATED MACULAR DEGENERATION (AMD)

 

About AMD

  • AMD is a leading cause of vision loss in older adults (>50) around the world. It may advance slowly or progress rapidly.
  • AMD gradually affects the macula, the central part of the retina that provides sharp, central vision needed for seeing objects clearly and to see colour.
  • The vision loss makes it difficult to recognize faces, drive a car, read, or do close work, such as sewing or fixing things around the house.
  • AMD does not cause complete blindness. Patients will still be able to see using their side (peripheral) vision.

Figure 1: Structure of eye

Types of AMD

  • Early AMD is often called ‘dry’ AMD, while late or more severe disease progression is often referred to as ‘wet’ AMD. Either form can advance & cause vision loss.
  • Dry AMD:
    • More common (80% of all cases), and (typically) milder form of AMD.
    • It is important for individuals with dry AMD to have their eyes examined regularly because it may eventually develop into the more severe wet form.

Figure 2: Drusen accumulate in the tissue beneath the macula

 

  • Wet AMD:
    • Late, or wet, AMD is characterized by rapid loss of central vision caused by bleeding under the macula by abnormal new blood vessels.
    • Although the wet form of AMD accounts for only 20% of all AMD, the risk of severe sight loss is much greater, being responsible for 90% of severe vision loss caused by AMD.

 

Prevalence

  • In Asian populations, the prevalence of early AMD is 6.8% & late AMD is 0.56%.

 

Causes

  • Age                            Ÿ Smoking
  • Poor nutrition               Ÿ Hypertension
  • Obesity and inactivity    Ÿ     Sun exposure

 

Symptoms

  • In its early stages, AMD may not have symptoms.
  • Straight lines start to appear distorted (usually the first sign)
  • Dark, blurry areas or white out appears in the centre of vision.
  • Scotoma (a dark spot in the centre of a visual field surrounded by a distorted image).

 

Figure 3: Normal vision and the same scene as viewed by a person with AMD

 

Diagnosis

  • Annual eye checks for AMD for those over 60 so early symptoms can be recognised.
  • Eye exams include the following tests:
    • Visual Acuity Test
    • Dilated ophthalmoscopy
    • Amsler Grid
    • Angiography
    • Optical coherence tomography (OCT)

Figure 4: Amsler Grid and what it might look like to someone with AMD

Treatment

  • The goal of treatment is to stop further vision loss. Unfortunately, in most cases, damage that has already occurred cannot be reversed, making early detection important for vision preservation.
  • While there is currently no cure for dry AMD, taking a specific formulation of antioxidants and zinc may slow the progression of the disease.
  • For wet AMD, medical treatments are available that can stop deterioration or even restore some lost vision.
    • Anti-VEGF Treatments
      • The drugs are injected into the eye every month and inhibit the growth of new blood vessels.
    • Photodynamic Therapy with laser
    • Submacular haemorrhage Displacement Surgery

 

Prevention

  • The following suggestions will help protect vision, improve overall health, and potentially lower the risk of developing AMD:
    • Eating a varied and nutritious diet that includes leafy green vegetables, fruit, fish, and food containing vitamin D, E, and C, beta carotene, lutein, and omega-3 fatty acids.
    • Getting regular exercise.
    • Maintaining a healthy weight.
    • Keeping blood pressure at a normal level and controlling other medical conditions.
    • Not smoking.
    • Preventing overexposure to sunlight (wide brimmed hats & sunglasses)
    • Regularly visiting an eye care professional for comprehensive eye exams.
    • Performing an Amsler Grid test at home.