Age Related Macular Degeneration

 

Age Related Macular Degeneration

 

As diabetes is a systemic disease, optimal control of blood sugar as well as blood pressure and cholesterol levels are still very important in the treatment of diabetic retinopathy. However, progression of retinopathy may occur despite all medical efforts. If diabetic retinopathy is detected early, treatment with laser photocoagulation may stop continued damage. Even in the advanced stages of the disease, laser treatment can reduce the chance that a patient will have severe visual loss.

Laser treatment is used to seal or obliterate the abnormal leaking blood vessels. This procedure focuses a powerful beam of laser light onto the damaged retina. Small bursts of the laser energy seal leaking vessels and form tiny scars inside the eye (Figure 6). The scars reduce new vessel growth and cause existing ones to shrink and close. Laser treatments are usually carried out in an outpatient setting.

Figure 1: Normal vision (left) and vision with AMD (right)

 

Dry AMD

 

As diabetes is a systemic disease, optimal control of blood sugar as well as blood pressure and cholesterol levels are still very important in the treatment of diabetic retinopathy. However, progression of retinopathy may occur despite all medical efforts. If diabetic retinopathy is detected early, treatment with laser photocoagulation may stop continued damage. Even in the advanced stages of the disease, laser treatment can reduce the chance that a patient will have severe visual loss.

Laser treatment is used to seal or obliterate the abnormal leaking blood vessels. This procedure focuses a powerful beam of laser light onto the damaged retina. Small bursts of the laser energy seal leaking vessels and form tiny scars inside the eye (Figure 6). The scars reduce new vessel growth and cause existing ones to shrink and close. Laser treatments are usually carried out in an outpatient setting.

Figure 2: Dry AMD

 

Wet AMD

 

The wet form of AMD affects only 10% of individuals with AMD but is responsible for the majority of visual loss in this disease. There is a growth of a network of abnormal blood vessels under the retina (Figure 3) and when these bleed, there is a sudden loss of central vision. The blood does eventually get reabsorbed but leaving behind permanent scarring and irreversible central vision loss. A subset of wet AMD known as Polypoidal Choroidal Vasculopathy(PCV) seems to be more common in our Asian population. There is also bleeding from abnormal vessels under the retina but in this case, the vessels can be found in clusters or ‘polyps’.

Both these types of AMD often co-exist. Patients who have wet AMD will invariably have signs of dry AMD as well. However, patients with dry AMD do not always progress to develop the wet form of the disease and there is no way of telling which patients will progress and which would not.

Figure 3: Sub-retinal bleeding in wet AMD

 

Risk Factors

 
  1. Age – AMD tends to affect individuals above the age of 55 years old and the risk of developing this disease increases with increasing age.
  2. Smoking – There is evidence from large clinical studies which suggests a strong link between smoking and the development of AMD
  3. Family history – There is also strong evidence from studies suggesting a genetic component in this disease. Several genes have been found to be strongly associated with the development of AMD.

How to detect AMD?

 

AMD only affects the central vision, hence, symptoms of disease can range from mild central blurring todistortion of images or a complete ‘blind spot’ in the centre of vision.An effective way of detecting AMD is through regular eye checkups with your ophthalmologist particularly if there are associated risk factors. There are also sophisticated investigations which can be carried out to evaluate the extent of disease involvement and these tests include Fundus Fluorescein or Indocyanine green (Figure 4) angiography where a dye is injected into a vein in the arm, and photographs of the retina are taken as the dye is carried in the blood stream to the eye. Another very detailed scan of the eye called Optical Coherence Tomography (Figure 4) can be done as well.

Figure 4: Colour photo of macula (top left),
FFA image (top right) and OCT (bottom)

 

Treatment of AMD

 

Dry AMD – In advanced dry AMD, there is currently no form of treatment which can prevent visual loss. However, in the earlier forms of dry AMD, there is strong evidence that taking a oral formulation of anti-oxidants and zinc can reduce the risk of progression to advanced AMD. This evidence came from a large clinical trial called the Age Related Eye Diseases Study (AREDS) and the supplements found to be beneficial are called the AREDS formulation and consist of Vitamin C, Vitamin E, beta-carotene, zinc and copper. Bear in mind that this benefit was only found in individuals with high risk of developing advanced AMD and was shown to reduce the risk by only 25%. The AREDS 2 study is now ongoing to evaluate the benefits of omega 3 fatty acids, lutein and zeaxanthin (macular xanthophylls) for AMD and results should be expected in the next couple of years.


Wet AMD – In the past, treatments available could only slow down the process of visual loss in this disease. These treatments included laser surgery and photodynamic therapy. More recently, there have been a development of a new group of drugs for injection into the eye (Figure 5). These group of drugs are known as anti-VEGF agents (Vascular Endothelial Growth Factor). From large clinical trials, it has been shown that this growth factor is in abundance in wet AMD, and regular injections of anti-VEGF agents can prevent significant visual loss in the majority of patients and even improve vision in up to a third of them.

Figure 5: Commonly used anti-VEGF drugs

 

What exactly is an intravitreal injection?

Gruesome as it may sound, this does involve "sticking a needle” into the eye and releasing specific drugs into the vitreous cavity. However, it does not hurt as much as most people think and it literally takes seconds to perform. It is used for the treatment of a variety of eye diseases but in recent years, it has revolutionized the management of AMD and has a significant impact not just on affected patients but also on retinal surgeons’ lives!!

The "Revolution"

The rise of intravitreal injections started in 2004 when intravitreal Macugen was first used in the management of AMD. This drug was developed to inhibit vascular endothelial growth factor (VEGF) which is a growth factor involved in the development of blood vessels. This had modest effect on the disease but the following year when Avastin (another inhibitor of VEGF) was first used to treat AMD, the revolution truly took off!

This was the first time there was any treatment that could actually improve vision in people with wet AMD. From Avastin, another drug came into the market in 2006 – Lucentis. This was a designer drug specifically manufactured to treat VEGF driven eye diseases as compared to Avastin (which was a cancer drug for metastatic bowel cancer).

The impact of this ‘revolution’ extended beyond its positive effects on patients but also the increased workload for retinal surgeons as these injections had to be given every month in order to maintain its efficacy. There were also far reaching consequences for healthcare services in some countries as reimbursement for this very expensive drug burned very large holes in the healthcare budget!

Since 2012, another anti-VEGF has been introduced called Eylea. This drug is supposedly longer lasting and therefore, patients may not need injections so often.


Prevention better than cure

It is always better to catch the disease in its early stages and ideally, if it could be prevented, all the better!

  1. If you have AMD, you should have a complete eye examination at least once a year by your eye specialist.
  2. If you have a family history of AMD, regular eye checkups also plays an important role
  3. Your lifestyle can impact on your risk of developing AMD:-
    • Don’t smoke
    • Have a healthy diet – green leafy vegetables and fish
    • Watch your weight
    • Exercise regularly