Dr Jacob Cheng
Specialty: Ophthalmology
Clinic: Eagle Eye Centre Pte Ltd (EEC)
Address: 820 Thomson Road, Mount Alvernia Hospital, Medical Centre Block B, #02-11/17, Singapore 574623
Tel: +65 6456 1000 / +65 6324 5393
Website: www.eagleeyecentre.com.sg

Age-related macular degeneration (AMD)

1) What is macula?

The retina is the light-sensitive tissue at the back of the eye, similar to that of a film in a camera. The retina is made up of many cells, called photoreceptors. Images are captured by these photoreceptors on this retina or ‘film’. They are converted to nerve signals and sent to the brain to be viewed as pictures. The centre of this retina is called the macula. It enables us to see fine details and differentiate colour. It also enables us in our daily detailed activities like reading, writing and driving.

2) What are the types of AMD?

There are two forms of age-related macular degeneration: dry and wet. 

Dry or non-exudative AMD is the more common form, affecting majority of patients with AMD. As a person gets older, these photoreceptors slowly fail to function properly. This results in abnormal deposits or debris, called drusen, to accumulate under the retina. Fortunately, these deposits rarely cause visual loss or blindness. However, in some patients, the photoreceptors slowly degenerate with time, resulting in an advanced form of dry AMD called geographical atrophy. In a small group of patients, patients with drusen can progress to develop wet AMD. Both advanced form of dry AMD and wet AMD can cause visual loss. 

Wet or exudative AMD accounts for 10% to 15% of cases, but is responsible for the majority of vision loss. This is due to growth of abnormal blood vessels under the retina called Choroidal Neovascularization (CNV). These new blood vessels are very fragile and may leak fluid or blood. This results in scarring that causes rapid and severe visual loss. Another variant that is commonly seen in this part of the world is called Polypoidal Choroidal Vasculopathy (PCV). This condition frequently results in large amount of bleeding and leakage under the retina. 

3) What are the risk factors?

a) Non-Modifiable Risk Factors:
Age
Genetics or family history 

b) Modifiable Risk Factors:
High fat diet
High blood pressure
High levels of cholesterol in the blood or hyperlipidaemia
Obesity
Smoking
Ultraviolet or sunlight exposure 

4) What are the symptoms?
·         Blur vision
·         Central loss of vision (scotoma) or areas of black patches/ shadows
·         Distortion of vision or metamorphopsia, where a straight line appears wavy

5) How do I monitor symptoms?

The Amsler Grid Test is used to monitor the macula. This consists of a large square with multiple small, regular squares. The centre of the large square is a black dot for the patient to focus on. A patient with normal vision focusing on the centre black dot should notice that the surrounding lines and squares are regularly spaced. If there are abnormalities, for example, missing black dot or squares, or waxy lines, a consultation with an ophthalmologist is necessary.

 

6) What can I do to reduce my risk of developing AMD?

Target the modifiable risk factors by changing our lifestyle:
·         Have a healthy diet of fish, green, leafy vegetables and reduced fats.
·         Take medications to control high blood pressure and elevated cholesterol.
·         Stop smoking.
·         Exercise to reduce weight.
·         Wear sunglasses to decrease sunlight exposure.

 

7) How to diagnose AMD?

Fluorescein angiography (FFA) is a procedure that involves injection of a dye and taking multiple photos of the retina as the dye passes through the vessels. This allows for the differentiation between normal and abnormal vessels, thus enabling localization and treatment to the abnormal vascular structures. 

Indocyanine green angiography (ICG) is another procedure that also involves injection of a dye and taking multiple photos. However, this requires a different dye as compared to FFA and allows deeper structures to be imaged, e.g. in the diagnosis of PCV. 

Optical coherence tomography (OCT) is a diagnostic tool that allows a quantitative measurement of a cross-section image of the retina. This is useful for monitoring purposes as well as diagnosis for more complex cases.

 

8) What are the available treatments?

How can I treat dry AMD?
There is currently no proven effective treatment for dry AMD.  

How can I treat wet AMD?
As for wet AMD, there are a few options but none of these is a cure.

Laser
This involves applying a focused beam of high-energy laser to the leaky blood vessels.  However, this will also destroy surrounding health tissues and cannot be used for blood vessels directly under the centre of the macula. 

Photodynamic Therapy (PDT)
This is a two-step procedure. The first involves injection of a drug called verteporfin (Visudyne) into the blood stream. The drug is pooled in the abnormal leaky blood vessels but not on normal vessels. The second step involves applying a ‘cold’ laser to activate the drug on these abnormal blood vessels. This way, the abnormal vessels will be closed and the normal tissue will not be affected, as they do not collect the drug. 

Anti-VEGFs
This is a recently discovered new group of drugs, called anti-VEGF (anti-Vascular Endothelial Growth Factor). By injecting the drug directly into the eye using a small, fine needle, it has been shown to be effective in a condition called Age-related Macular Degeneration by causing regression of the abnormal blood vessels. This has been also been used in patients with diabetic retinopathy. It can control retina swelling and prevent further bleeding in the eye. This is promising treatment that may result in improvement of vision, but results vary in individuals. However, injections may have to be repeated on a monthly basis for optimal results. An example of this agent is Lucentis (ranibizumab) (www.lucentis.com). Due to the high cost of Lucentis, a close chemical alternative of Lucentis, Avastin (bevacizumab), can be used. 

Avastin is a drug used for patients with colorectal cancer. It is used ‘off-label’ for patients who cannot afford Lucentis.  

Both of these drugs are injected directly into the eye known as an intravitreal injection.

 

9) Are there nutrients I can take?

Studies have proven that vitamin supplementation with high doses of antioxidants and other minerals slow the progression of advanced macular degeneration. In some studies, lutein, zeaxanthin, and fish oil have also been associated with macular protection. A more conclusive study is currently underway to show the benefits of these supplements.
 

10) What be done when I already have poor vision from advanced AMD?

Fortunately, macular degeneration does not lead to total blindness. Usually, only the central vision is damaged. Even in advanced cases, the peripheral vision is still very well preserved, allowing for ‘navigational’ vision. 

There are many low-vision aids that can help. These consist mainly of magnifiers, both for near and far distances. They range from simple desktop glass magnifiers or telescopes, to more sophisticated ones like computer screen readers.

 

11) What can Eagle Eye Centre offer?

At Eagle Eye Centre, we perform a complete ocular examination, including visual acuity, slit lamp, intraocular eye pressure checks and dilated fundal examination. We offer a proper diagnosis and personalized treatment for your condition after your assessment.  

With the latest imaging techniques, including FFA, we offer an accurate diagnosis of stages of the diabetic retinopathy. In addition, we have a state-of-the-art spectral domain OCT, Zeiss Cirrus (www.meditec.zeiss.com/cirrus) which can deliver exquisite high-definition images of structures inside the eye.
 

We can perform laser from the latest PASCAL laser (www.optimedica.com). This is the latest and most advanced machine for precise, safe and efficient delivery of laser into the eye with less pain and side effects.

We have various intravitreal injection options between Avastin and Lucentis. We also offer counseling with regards to diet and lifestyle modifications. We also have a wide range of low-vision aids to help overcome various visual inconveniences.

Disclaimer: The information in this website is for general health education only. Please consult a doctor if you have symptoms or questions on medical conditions or illnesses.

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