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Age-related Macular Degeneration

Don’t lose sight of this stealthy vision stealer

iStock_000005542177_LargeAge-related macular degeneration (AMD) accounts for 8.7% of all blindness worldwide, and is the most common cause of blindness in developed countries. The condition will become more prevalent worldwide as a consequence of the increase in ageing populations. It is projected that this disease will affect around 196 million by 2020, and about 288 million by 2040.

Two Types of AMD

AMD is a disease that gradually and stealthily destroys central vision. It affects the central area of the retina – the light-sensitive layer of the eye (the macula) – which allows us to see fine details. AMD does not hurt, but it causes cells in the macula to die.

There are two types of AMD: wet and dry.

Wet AMD

Wet AMD happens when abnormal blood vessels grow under the macula. These new blood vessels often leak blood and fluid. Wet AMD damages the macula quickly. Seeing straight lines as crooked or blurred, especially in the central part of vision, is a common early symptom.

Dry AMD

Dry AMD happens when the light-sensitive cells in the macula slowly break down. One of the most common early signs of dry AMD is drusen. Drusen are yellow deposits under the retina. They are often found in people over the age of 60. As the disease progresses, there is associated death of retinal cells near the drusen, which leads to slow and progressive central vision loss.

Figure 1. Normal retina and macula

Figure 1. Normal retina and macula

Figure 2. Dry AMD with drusen in macula

Figure 2. Dry AMD with drusen in macula

Figure 3. Wet AMD with bleeding under the retina

Figure 3. Wet AMD with bleeding under the retina

 

 

 

 

 

 

 

The dry form is much more common than the wet form. More than 85% of all people with AMD have the dry form. However, if only advanced AMD is considered, about two-thirds of patients have the wet form. As almost all vision loss comes from advanced AMD, the wet form leads to significantly more vision loss than the dry form. The dry form can also suddenly turn into the wet form, even during early stage AMD. Unfortunately, there is no way to tell if or when the dry form will turn into the wet form.

Risk Factors

As the name suggests, the greatest risk factor in a person developing AMD is age. Although AMD may occur during middle age, studies show that people over the age of 60 are clearly at greater risk than other age groups. For instance, a large study found that people in middle age have about a 2% risk of getting AMD, but this risk increases to nearly 30% in those over the age of 75. Other risk factors include smoking, obesity, and a family history of having the condition. Many studies have reported that smoking may increase the risk of AMD, and that the speed of disease progression is comparatively slower in ex-smokers than active smokers.

Treating AMD

In general, all treatments for AMD are essentially to slow or halt the progression of the disease and to reduce or eliminate the exudative features. Whether this translates into visual stabilisation or improvement will depend on the pre-treatment vision and size of the lesion. Therefore, earlier diagnosis and timely treatment are the keys to stabilising or improving vision.

There is currently no treatment for advanced dry AMD. For individuals who are at high risk of advanced dry AMD, they may be recommended to take the AREDS (Age Related Eye Diseases Study) formulation that can reduce the risk of developing advanced AMD by about 25%.

Wet AMD can be treated either by injecting medication into the eye or by laser. Thermal laser therapy (based on the Macular Photocoagulation Study) was the first approved treatment for wet AMD. This advocated application of laser to destroy leaky abnormal blood vessels, but in the process, the laser also destroyed normal retinal cells, leaving the patient with a stable central visual defect.

Photodynamic therapy (PDT) with a dye called verteporfin (Visudyne) can also be used to treat wet AMD. It involves injecting a drug into an arm vein. The drug is absorbed by the abnormal blood vessels in the eye that cause wet AMD. Next, a cold laser is shone into the eye, activating the drug, and destroying the blood vessels. This procedure gained popularity as it destroys the abnormal vessels and does not damage normal retinal tissue.

Recently, drugs known as anti-vascular endothelial growth factors (anti-VGEF) were introduced in the treatment of wet AMD. Not only was the disease stabilised, but patients also saw a substantial improvement in vision. Anti-VEGFs (bevacizumab or Avastin, ranibimizumab or Lucentis, aflibercept or Eylea) are drugs that are injected into the affected eye. Patients may need multiple monthly injections to stabilise the disease. Sometimes, the treatment options are combined in certain individuals, especially if the disease activity is very severe.

Lady having eye test examinationA LOOK AT THE NUMBERS

AMD at a Glance

  • 8.7% of all blindness worldwide is caused by AMD
  • It could affect 196 000 000 by 2020, and 288 000 000 by 2040
  • The middle-aged have a 2% risk of getting AMD
  • Risk increases to 30% in those > 75 years

AMD Awareness

Many of our elderly delay early diagnosis due to lack of awareness of this condition. A survey published by the department of Ophthalmology and Visual Sciences, Khoo Teck Puat Hospital (KTPH) in 2009, reported that only 7.3% of Singapore residents interviewed were aware of
AMD in 2006. The need for more awareness was addressed by a nation-wide AMD awareness initiative which conducted educational talks Falling vegetables for salad isolated on whiteand eye screenings for people above 55 years of age. A subsequent follow up study in 2011 by the team to look at the effects of the AMD awareness campaign organised by KTPH showed that the awareness levels for AMD in Singapore have increased by about four-fold over five years to 28%. This year, the AMD awareness week is organised between 11 and 19 October 2014. cigarette


How can I prevent AMD?

  1. Stop smoking
  2. Eat green leafy vegetables
  3. Adopt a healthy lifestyle with good diet and regular exercise
  4. Go for regular eye checks after the age of 55

 

For more information about AMD Awareness Week 2014, visit www.ktph.com.sg.

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Dr Bakthavatsalu Maheshwar is a Senior Staff Physician, Department of Ophthalmology and Visual Sciences, at Khoo Teck Puat Hospital, Singapore.
Posted by ezyhealth on Oct 13 2014. Filed under Eye Health. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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