Age-related macular degeneration (AMD) is an eye condition that usually affects those aged 45 and above. People with AMD experience blurred central vision and are unable to see clearly what is in front of them. This affects a person’s ability to read, write and differentiate colours, among other things.
The macula is the part of the retina that is responsible for our central and fine vision. We use this part for reading fine prints. The macula is supported by many active cells called photoreceptors that signal to the brain what we are seeing.
These cells produce waste materials which need to be transported out of the eye. With increasing age, these products may accumulate in the eye. In addition, some tissue layers may also thin down with age. These changes eventually manifest themselves as AMD.
In very broad terms, AMD can be divided into the ‘dry’ type and the ‘wet’ type. Dry AMD is much more common and often does not require treatment as it tends to progress slowly. Wet AMD, on the other hand, usually requires urgent treatment as it can cause irreversible damage to the central vision in weeks or months.
How common is AMD in Asians?
AMD is uncommon in people under 45, but becomes increasingly common in people over 70. With Singaporean and Asian populations enjoying a longer life expectancy, AMD is expected to increase significantly over the next few decades.
A recent study reported the prevalence of early and late AMD in Asian populations aged 40-79 years were 6.8% and 0.56% respectively. However currently there are no reliable estimates of AMD in Asian persons aged above 80 years.
AMD is also more common in females, in people with a family history of AMD and in people with cardiovascular diseases.
How can AMD be treated?
Retinal specialists often perform special investigations called retinal angiography to study the disease in detail before recommending treatment.
Wet AMD can be stabilised through treatments such as injecting medications (a class of medicine called anti-vascular endothelial growth factors) into the eye, thermal laser and photodynamic therapy (a drug-assisted laser treatment). Repeated treatments are often needed before the disease can be fully stabilised.
However, not everyone can recover one’s vision. Therefore it is important to see an eye doctor as soon as symptoms are noted so that diagnosis and treatment can be given in a timely manner.
There is currently no satisfactory treatment for dry AMD. However, many studies are looking into new drugs for dry AMD. Hopefully these will become available in a few years.
What are the symptoms of AMD?
Patients with early AMD may not notice any symptoms themselves, but the condition may be picked up during an eye examination. Dry AMD may be associated with mild blurring of central vision, which does not progress quickly.
However, development of wet AMD is usually associated with sudden and rapid loss of central vision and /or distortion. If untreated, the visual loss usually progresses quickly over weeks.
What causes AMD? Is there anything one can do/eat to prevent it?
Many factors are related to AMD. These include hereditary/genetic factors, dietary factors and cardiovascular diseases (such as hypertension, high cholesterol, diabetes). Smoking has also been shown to increase the risk of AMD.
The Age-Related Eye Disease study (AREDS) is the only large-scale randomised controlled clinical trial to show a 25% beneficial effect of nutritional supplement in reducing the risk progression to advanced Age-related macular degeneration (AMD) in patients who already have at least intermediate AMD. The AREDS formulation contains vitamins C, E, ?-carotene, and zinc with copper. However the benefit of such preparation for individuals with no AMD or only early AMD to start with, is still unclear.
Other supplements that have been associated with lower risk of AMD include macular xanthophylls (Lutein and zeaxanthin) and high dietary intake of omega-3 fatty acids (DHA/EPA). Fish is a good source of omega-3 fatty acids. Once study showed that a minimum bi-weekly fish intake was associated with reduced risk of AMD.
Will staring at a computer screen daily for work increase one's risk of developing AMD as one grows older, given that blue light is said to be a cause of AMD?
Unfortunately, computer work is becoming almost an indispensable part of modern life. The glare from the screen does cause irritation and eye strain. However there are no studies directly linking computer work and the development of AMD.
It is advisable though, to take regular breaks from the computer screen to allow the eyes to relax.
What is the prognosis for a person who is diagnosed with AMD?
With advances in treatment options, prognosis has improved dramatically over the past decade. As recently as 15 years ago, with no satisfactory treatment for wet AMD available, roughly half of patients with wet AMD will become blind after 2 years.
Currently stabilization is achievable in the majority once treatment starts, i.e. we can stop the condition from worsening, and at least maintain the level of vision at presentation. Hence, how soon a patient seeks treatment will have a direct impact on his prognosis. However, improvement of vision is only achievable in about 30 to 50 per cent of patients.
Prognosis of a person diagnosed with dry AMD is usually good. This is because dry AMD usually progress very slowly. However currently there is no satisfactory treatment to reverse dry AMD.
This article was contributed by Dr Gemmy Cheung, a consultant ophthalmologist in Vitreo-Retinal Service at Singapore National Eye Centre.