What is Macular Degeneration?
Age-related macular degeneration (AMD or ARM) is the most common cause of irreversible vision loss in people over the age of 50 years in Australia, affecting approximately 1 in 7. Age-related macular degeneration (AMD) is a degenerative disorder affecting the macula, a part of the retina responsible for detecting light.
On the inside of the eye, the Retina is a thin layer of cells capable of turning light into an electrical impulse, to be sent to the brain and processed into an image. The central portion of the retina is called the macula, and is responsible for detecting light and producing an image for the central portion of your vision. The macula zone of the retina works much harder than the rest of the retina, as your central vision has a much higher level of detail than your peripheral vision. Due to this, the macula tends to wear out much faster than the peripheral retina.
What causes Macular Degeneration?
The main cause of Macula Degeneration is age. Efficiency of important cells at the macula is significantly reduced with age and can affect retinal blood flow, nutrition and waste management. These functions become reduced, the macula starts to wear out and can become damaged.
A result of having a damaged macula will produce poorer quality vision, as light entering the eye is no longer being detected as effectively. Macula Degeneration continues to worsen as its cells age. Long term, cells at the macula become irreversibly damaged and die, resulting in large portions of central vision loss. This is due to light no longer being detected in certain areas of the retina. In a small proportion of patients, macula cells struggling under age-related stress will prompt the quick growth of new blood vessels in the retina. These blood vessels, however, are often leaky, and leak blood and fluid into the retina causing further permanent damage.
It is important to remember that humans are living much longer than we used to, so we are seeing much higher rates of age-associated health conditions, Macula Degeneration included.
Not all people show signs of Macula Degeneration, as every individual ages at a different rate. Similarly, as some people sprout grey hairs earlier than others, some maculas show signs of aging earlier than others. It would be fair to assume that if we all lived long enough, at some stage we would all develop Macula Degeneration.
What are the risk factors of AMD?
Macula Degeneration is ultimately caused by aging, as it is caused by the wearing out of an important part of the eye. There are, however, certain additional risk factors which make you more likely to develop Macula Degeneration.
These risk factors include:
- Older age: (>60 years) The strongest risk factor for AMD. The older the retinal tissue, the less functional it becomes.
- Family history: Family History of Macula Degeneration/genetics. Most people have a similar body structure to their family members. If your parents started getting grey hair at 50, it’s likely that you will likely show aging signs of grey hair around that age also. Similarly, if you have parents whose macula/retina showed aging signs at 80, it’s not unlikely that your retina will also start to show aging signs around the same time.
- Smoking: Smoking is the strongest risk factor associated with Macula Degeneration and is something that we we can change on our own. Studies have shown smoking at least doubles the risk of developing Macula Degeneration. There is a direct correlation between current smoking and the number of cigarettes a person has smoked during their life and their risk of late stage AMD. Smokers, on average, develop age-related macular degeneration 5 to 10 years earlier than non-smokers.
- High blood pressure (hypertension): several case control studies have identified a significant association between high blood pressure and developing severe Macula Degeneration
- Cardiovascular disease: Has also been proposed to approximately double the risk of severe Macula Degeneration.
- BMI of 30kg/m2 or higher: There has also been some link to suggest being overweight/obese increases the risk of severe Macula Degeneration.
Although the scientific evidence for these last three risk factors are not as extensive as those listed above, it seems to be that a healthy lifestyle with regular exercise and a balanced healthy diet helps to prevent macula aging.
Risk factors with less convincing scientific evidence:
- Diet : A diet low in omega 3 fatty acids, vitamins, carotenoid and minerals. There have been a number of studies showing interactions with diet and Macula Degeneration, particularly from the Age-Related Eye Disease Studies 1 and 2 (AREDS).
- A diet high in macular carotenoids (zeaxanthin and lutein) and omega-3 long-chain essential fatty acids may be protective against Macula Degeneration.
- Diets high in fat : (saturated fats, trans fats and omega-6 fatty acids) may contribute to Macula Degeneration developing. A diet high in fruits, vegetables, chicken, nuts and with less red meat, seems to be associated with a lower risk of severe Macula Degeneration.
- Lack of exercise : It has also been observed that more frequent vigorous exercise was possibly associated with lower risk of Macula Degeneration.
How is Macular Degeneration detected?
Early detection of Macula Degeneration is very important, as it is difficult to repair the macula once it has been damaged. Early stages of Macula Degeneration are often difficult for an individual to detect themselves, as it tends to have no symptoms. Usually, early Macula Degeneration does not affect your vision or retinal function at all. It is, however, detectable via retinal examination by an eyecare professional using Retinal Imaging/Fundoscopy, Ocular Coherence Tomography and Autofluorescence Imaging.
Retinal Imaging and Fundoscopy
As mentioned on Our Technology page, Retinal Imaging involves high definition viewing of the retina. With a high definition view of the macula, we can detect and compare degenerative change. Several signs of degeneration detected using Retinal Imaging include: drusen (waste buildup,) pigment changes, neovascularisation (growth of new blood vessels,) bleeding and atrophy (loss of retinal tissue.) “Fundoscopy” is where an eyecare professional views this same retinal image in real time, behind a microscope.
Fundus Autofluorescence (FAF)
Using specific wavelengths of light (blue or green light,) the presence of specific light absorbing molecules within the retina can be detected. High numbers of light absorbing molecules will create a brighter image, and lower numbers will produce a darker image. When retinal tissue is under stress or dying, different levels of these molecules are present, hence this imaging technology can determine how healthy the retinal tissue is. In Macula Degeneration, retinal tissue is under stress and not performing at full capacity, so Fundus Autofluorescence can help determine if the retinal condition is worsening.
Near Infra-Red Imaging (NIR)
Similar to the mechanism of Autofluorescence, Infrared light will be absorbed by specific molecules in the retina, highlighting areas where the retina is changing.
Ocular Coherence Tomography (OCT)
The retina has many important layers, all affected differently in different ocular conditions. As opposed to standard retinal imaging, which produces a two dimensional flat image of the retina, OCT scanning technology allows for observing the retina in three dimensions. By creating hundreds of cross sections, this technology shows all of the retinal layers, rather than a flat image. This technology has enabled huge recent advancements in the detection and treatment of Macula Degeneration.
What are the symptoms of Macular Degeneration?
Although early Macula Degeneration usually has no symptoms, there are several signs to look out for. Some patients with early Macula Degeneration have reduced contrast sensitivity and have difficulties with dark adaptation e.g. difficulties reading in dim light or adjusting from different lighting conditions (moving inside after being outdoors.)
Another symptom is that your glasses no longer improve your sight as much as they used to. A central spot or distortion in the centre of your visual field may be noticed. Words or objects may appear distorted (door frames not straight, items appearing smaller or larger than they should).
Some patients notice they have difficulty with normal everyday visual tasks/activities (watching television, going down stairs, reading or recognising people). Some people with severe Macula Degeneration develop visual hallucinations (Charles Bonnet syndrome).
Treatment for Macular Degeneration
As there are currently very few effective treatments for advanced Macula Degeneration, prevention is very important. Managing any modifiable risk factors is the best way to protect yourself from developing macula changes. Quit smoking, eat a balanced, healthy diet (rich in green leafy vegetables, fish and antioxidants,) look after your systemic health (blood pressure/cholesterol/weight,) and exercise regularly!
With the correct instructions from your Optometrist, it is possible to monitor and detect changes in your central vision at home using an Amsler Grid.
There are known supplements on the market, which have been shown to help slow the progression of Macula Degeneration. They do not, however, stop it from developing. They also do not assist in slowing advanced Macula Degeneration. Supplements with reasonable scientific evidence must include the AREDSII Formula. This includes 500mg of vitamin C, 400 international units of vitamin E, 80mg zinc as zinc oxide, 2mg copper as cupric oxide, 10mg lutein, 2mg zeaxanthin.
Intravitreal Injections (anti-VEGF therapy)
In cases where the macula has developed new blood vessels (neovascularisation), eye injections are required. These injections act to prevent the growth of these new vessels, allowing the leaks/bleeds within the retina to resolve. If leaky blood vessels within the eye are left unmanaged, they can cause a very rapid decline in vision, which is irreversible. Often, multiple injections are required over a long period of time, to ensure the blood vessels to not continue to leak fluid and damage the retina.
There are many future treatments on the horizon, as lots of research is going into finding more effective ways of preventing and treating Macula Degeneration. There are clinical trials currently underway, exploring the effect of several medicinal and laser treatments for the management of intermediate and advanced Macula degeneration. We are watching this space closely for when new options may become available.
Although late stage Macula Degeneration has no treatment, there are ways to adapt to living with low vision. Magnifiers and Low Vision aids are available to help get the most out of eyes with retinal damage. Good lighting is also important, as higher contrast will assist. Damaged retinas are often more glare sensitive, so sun protection/tinted glasses with an increased coverage can help block out glare.