Age-related Macular Degeneration (AMD)
What is the macula?
The macula is the central area of the retina (i.e. the light-sensitive layer at the back of the eye) and is responsible for enabling our central detailed vision as well as our colour vision. Whenever we look at something, we are using the macula in order to see the detail of what we are looking at and so it is where our best vision is derived from. For obvious reasons, it is a very active and integral part of the eye.
What is Age-related Macular Degeneration (AMD)?
The retina, like any tissue in the body, loses its metabolism over time and so as we age it does not function in the same way that it will have done when we were younger. It struggles to remove its metabolic waste products and when this happens we begin to observe changes in the colour of the retina and also the appearance of yellow spots referred to as drusen. These progressive changes can occur anywhere within the retina but it is when they occur at the macula that it becomes more serious as this can then begin to impact our central detailed vision and, more to the point, the best vision we are capable of achieving. This signals what is commonly referred to as Age-related Macular Degeneration (AMD).
AMD is the most common cause of vision loss in people over the age of 55 years and it is a condition where both the prevalence and severity increase with age. By the age of 75 years, almost 15% of people will have this condition to some extent.
In what way does AMD affect vision?
AMD only affects the macula and so does not affect any area of the retina beyond the macula. This means that it alone will only ever affect our central detailed vision and not our peripheral vision. However, because our central detailed vision is essentially our best vision it can have quite a debilitating effect and people with the condition have to learn how to adapt to this vision loss, sometimes using a peripheral point of the retina to fixate with instead. Generally, the result of the condition is that it can cause increasing difficulty with reading, especially small print and in poor lighting conditions, and also with seeing and recognising faces.
The key point though is that AMD will never solely cause blindness or a complete loss of vision in the eye it is affecting.
What are the risk factors for AMD?
There are several risk factors associated with the development and/or progression of AMD and the following three risk factors are all supported by conclusive evidence. These are:
Typically the condition tends to affect people from the age of 55 years onwards, with its prevalence and severity increasing from this point.
If you have a positive family history of AMD then you are approximately 4 – 6 times more likely to develop AMD yourself than a person who does not have a positive family history of AMD.
It has been discovered that smoking increases the risk of AMD developing and/or progressing by approximately 2 – 3 times. However, cessation of smoking does reduce this risk.
Other risk factors where the supporting evidence is less conclusive include:
Caucasians have been considered to be at greater risk.
Females have been considered to be at greater risk (although this may be due to the fact that females are considered to live longer).
- Cardiovascular disease (CVD)
It has been suggested that this can increase the risk of AMD developing and/or progressing.
- Previous cataract surgery
The release of certain proteins during the operation has been associated with an increased risk of AMD developing and/or progressing.
- Ultraviolet (UV) exposure
Regardless of the weight of this risk factor, it is always important to protect your eyes from the effects of the Sun. This is best achieved by wearing sunglasses that will provide 100% UV protection (especially with respect to harmful UVA and UVB radiation).
It has been suggested that keeping a healthy balanced diet of coloured fruit and vegetables, particularly dark leafy green vegetables (e.g. spinach, kale, broccoli, cabbage, salad leaves etc.), can help to maintain macular pigment, which in turn is considered to help protect the macula. This also applies to egg yolks and oily fish such as mackerel and/or sardines. There are also a wide range of commercially available nutritional supplements that have been specifically formulated to have the same effect. However, the benefits of taking these are still very debatable.
Are there different types of AMD?
There are two types of AMD. These are:
- Dry AMD
This is the most common but least aggressive of the two types and is associated with a gradual loss of central detailed vision. Dry AMD is characterised by the presence of drusen (see above) and pigment changes at the macula. These changes progress slowly over months and years, causing a gradual degeneration or atrophy of the macular tissue. There is also the possibility that dry AMD may progress to become wet AMD.
- Wet AMD
This is the least common but most aggressive of the two types and is associated with a rapid loss of central detailed vision. Wet AMD is characterised by the growth of abnormal blood vessels at the macula. These abnormal blood vessels then leak, causing fluid and blood constituents to accumulate within the layers of the macular tissue. This causes a sudden and rapid loss (and/or distortion) of our central detailed vision and if left untreated could result in a scar that makes this permanent.
Is there any treatment for AMD?
As it stands, there is currently no treatment available for dry AMD although there is much going on in the way of research and clinical trials in an attempt to change this. Any treatment of dry AMD is generally with a view to advising about the risk factors (as it is possible for dry AMD to progress into wet AMD) and managing the symptoms associated with it. This could involve the use of low vision aids, both optical (e.g. magnifiers, telescopes etc.) and non-optical (e.g. additional lighting, large print etc.). There are also a number of local and national organisations available to provide information, advice and support to those who may be suffering from the condition (regardless of the type), examples including the Royal National Institute of Blind People (RNIB) and the Macular Disease Society.
Although there is no treatment available for dry AMD, it is possible to treat wet AMD provided that it is caught early. This is generally achieved by means of anti-VEGF (Vascular Endothelial Growth Factor) injections into the affected eye. VEGF itself is a protein that contributes to the growth of the abnormal blood vessels associated with wet AMD. Therefore, when an anti-VEGF agent is injected into the affected eye it binds with the VEGF and prevents this from happening. This in turn stops the accumulation of fluid and blood constituents within the layers of the macular tissue, preventing further loss of vision.
The anti-VEGF agents currently approved by NICE (the National Institute for Health and Clinical Excellence) are Lucentis and Eylea, the latter now generally being favoured over the former. Both require a minimum of 3x monthly loading doses and then regular follow-ups generally every 4 – 8 weeks with further injections being done when needed. However, there may come a point where treatment in this way may be ceased if it is no longer causing any improvement in the condition or the patient’s vision.
If you have any queries or concerns regarding anything pertaining to AMD then please do not hesitate to contact us.Back Next