Age-related Macular Degeneration (AMD)
Macular Degeneration, often referred to as Age-related Macular Degeneration (AMD or ARMD) as it typically affects the over 50s, is a condition that results in the gradual loss in a persons’ central field of vision. This is initially characterised by distorted or blurry vision in the centre of your line of sight. Eventually, if the condition remains untreated, it can result in an entirely blank area in your eyesight.
AMD is a disorder which affects the macula region of the eye’s retina. The macula is the small, but highly sensitive, part of the eye responsible for detailed central vision. It allows us to appreciate fine detail, helping us to perform tasks such as reading and driving.
Age-related Macular Degeneration occurs when the macula becomes damaged and stops functioning as normal. There are two forms of the condition, “Wet AMD” and “Dry AMD” and they differ in the way that this damage occurs. Wet AMD is the more severe of the two but conversely, if diagnosed promptly, is more treatable. However, before we look at the two forms of the condition in detail we should examine the symptoms that may suggest the presence of AMD.
How does AMD effect your vision
Symptoms & diagnosis of AMD
You should visit your optometrist if you begin to notice any of the following symptoms:
- Difficulty reading small print, even with you glasses on
- Hazy or distorted vision
- Seeing straight lines as wavy
- Sensitivity to bright lights
The optometrist can do some simple tests, if the results indicate the presence of AMD you will be referred to an ophthalmologist. Once such test is the Amsler Grid test; this comprises of an area of crossing vertical and horizontal lines, similar to graph paper, with a black dot in the centre. Patients sit 14 inches away from the grid and cover one eye. With the other eye they are told to focus on the black dot. If the grid lines appear wavy or distorted in some way it may indicate the presence of AMD. The Amsler Grid test can be done at home by anyone. A number of organisations have grid tests on their websites which are available to download.
If AMD is thought to be present the ophthalmologist will apply drops to dilute your pupils allowing them to clearly see the inside of your eye. Using a device known as a Slit-Lamp they will ask you to look in various directions whilst shining a bright light into your eye. This enables them to see any changes and/or damages to your retina. In some cases this is the only examination needed to determine whether or not you have AMD. In some cases a further test, called a fluorescein angiogram, may be needed to establish whether you have the wet or dry form of the condition.
A fluorescein angiogram is a method of taking pictures of the tiny blood vessels in the eye. A harmless yellow dye is injected into your arm which makes its way through the body to the eye, making the blood vessels visible. A series of pictures will then be taken of the back of your eye. The resulting images will allow your ophthalmologist to determine the severity of the condition and therefore which treatment path to take.
Wet and dry AMD
Wet and dry AMD do share a few common characteristics:
- They usually affect both eyes
- They do not affect peripheral vision and therefore neither will ever result in complete blindness
- Neither condition is painful
Dry age-related macular degeneration
Dry AMD, the more common of the two, is characterised by the slow accumulation of yellow deposits (drusen) in the macula. In small numbers these are not necessarily problematic but as they grow in size and number they lead to a distortion in your eyesight. When dry AMD becomes advanced, the light-sensitive cells in the macula thin and eventually atrophy, whereupon you may lose central vision.
Treatment of dry AMD
Unfortunately there are no treatments currently available for dry AMD. There is some evidence to suggest that high doses of various minerals (zinc & copper) and vitamin (A, C & E) supplements can slow the progression of the condition but they are not thought to be able to prevent its onset.
There have also been a number of recent studies looking at whether a low-intensity laser treatment could halt the degeneration of eyesight or prevent the onset of more serious forms of the disease. However the conclusion of the study by the National Eye Institute found that the treatment did not demonstrate any clinically significant benefits.
There are a few things that can help you to make the most of your remaining peripheral eyesight:
- Talk to you optometrist about getting a magnifier
- Find out whether you may be eligible to register as sight-impaired, as you may be entitled to some additional benefits
- The Macular Society offer training in alternative techniques of reading with you peripheral vision
Wet age-related macular degeneration
Wet AMD occurs when abnormal blood vessels grow and leak blood and fluid into the retina. The outcome of this is distorted vision, making straight lines look wavy, and blind spots. Unlike dry AMD, wet AMD can develop very quickly leading to rapid loss of central vision. Eventually the blood vessels scar, resulting in the permanent loss of central vision. Once the condition has reached this stage it is no longer treatable making it imperative that you seek advice as soon as you notice any of the symptoms.
Treatment of wet AMD
There are two main treatment options for wet AMD that are able to halt or slow the progression of the condition; anti-VEGF medicine and a laser surgery known as photodynamic therapy (PDT).
Vascular Endothelial Growth Factor (VEGF) is one of the naturally occurring chemicals responsible for the growth of new blood vessels in the eye that cause wet AMD. The anti-VEGF medicines work by blocking the chemical thus preventing the progression of the condition. In some cases the treatment has also been found to shrink the existing blood vessels, leading to an actual improvement in eyesight. Despite these advances, however, it is unlikely that your eyesight will be restored entirely. The medication needs to be injected directly into the eye, a procedure that is done under local anaesthetic.
There are two varieties of anti-VEGF medication available on the NHS, ranibizumab and aflibercept. There are also alternative drugs that are only available privately. Pegaptanib, one such option, typically costs around £9000 for a two year course of treatment.
- Ranibizumab (known under the brand name Lucentis) is administered as an injection once a month for three consecutive months. You will be monitored regularly and if, following this initial phase of treatment, there has been no improvement you might be given a further doses at regulated intervals. In patients where the deterioration fails to cease or slow the treatment will be stopped.
Potential side effects of Ranibizumab include discomfort and/or minor bleeding; inflammation of the eye; increased pressure in your eye and the sensation that there is something in your eye.
- Aflibercept (known under the brand name Eylea) is the more recently approved of the two medicines. As with ranibizumab, you will receive an injection once a month for three months. Thereafter the treatments are slowed to one every two months. After a year, your progress will be monitored and the intervals between injections increased. Generally speaking, aflibercept requires fewer injections in order to see progress than ranibizumab.
Side effects of anti-VEGF medicine
The potential side effects of both drug are similar and are usually easily managed. The most common are:
- Irritation and inflammation of the eye
- Slight bleeding at the injection site
- Mild pain
- Increased pressure in the eye
- The sensation of feeling like there is something in your eye
Are you eligible for anti-VEGF treatment?
The drugs are only prescribed to patients if there is clear evidence that they will improve or, at least, maintain their current level of eyesight. In order to be eligible patients need to meet the following criteria:
- A person should have at least 6/96 vision. This means they should be able to see something at six metres that normal eyesight could see at 96 metres. Worse than that and the treatment is unlikely to be effective.
- There should be no damage to the part of the eye responsible for seeing things in sharp detail (the fovea).
- The evidence suggest the condition is worsening (in some patients, wet AMD does not continually deteriorate).
- The affected area of the eye should not be too large
Photodynamic therapy (PDT)
Photodynamic therapy (PDT) involves the injection of a light sensitive drug, verteporfin which accumulates in the abnormal blood vessels in the eye. A laser is then shone onto the area activating the drug, causing clots that seal off the blood vessels. This process can slow down the damage to the macula and reduce, or even halt, further vision loss. The procedure is down on an outpatiuent basis and takes less than half an hour.
Side effects of photodynamic therapy
There are a few possible side effects following PDT:
- Because the drug used increases light sensitivity, there is the potential for sun burn in the days following the procedure. Patients should keep themselves covered up and wear sunglasses when outside.
- Inflammation or infection at the injection site
- Blurred or reduced vision
Are you eligible for photodynamic therapy?
The National Institute for Heath and Care Excellence (NICE) recommend that PDT be offered only in cases where there is a good chance of successful outcomes. As such, patients must match the following eligibility criteria:
- Candidates should have at least 6/60 vision, meaning they can see and object at six metres that normal eyesight can see at 60 metres.
- Candidates should be on the more severe spectrum of wet AMD