Macular Degeneration
Macular degeneration (MD) is the name given to a group of chronic degenerative retinal diseases that can cause progressive loss of central vision. It affects the ability to read, drive, recognise faces and perform any activity that requires detailed vision. MD is more common in older persons, and is commonly known as age-related macular degeneration (AMD).
MD is the leading cause of visual impairment in Australia, responsible for half of all cases of blindness. Approximately 1 in 7 Australians have signs of MD, and 17% of these will experience vision impairment ranging from mild to severe. Although macular degeneration is usually related to ageing and most frequently affects people over the age of 50, it is not a normal or inevitable part of the ageing process, and some forms of the disease can also affect younger people.
Macular degeneration is progressive and painless and although it can lead to legal blindness, it usually does not result in total or ‘black’ blindness.
How does MD affect your sight?
In the early stages of MD your sight may be unaffected. However, signs that the retina is being damaged can be detected by your eye care practitioner (optometrist or ophthalmologist), and this highlights the importance of regular eye examinations to detect AMD in its early stages.
Some people progress from early to late stage MD, where the condition causes loss of vision. Common symptoms of MD are blurred vision, distortion of straight lines, or a dark patch in central vision.
Types of Macular Degeneration
There are two types of macular degeneration: dry and wet.
The dry form is more common, affecting 85% of persons with AMD. It results from slow deposition of waste material from retinal cells underneath the macula. These waste products appear as yellowish deposits known as drusen. In turn these drusen cause thinning of the pigment layer of the retina (retinal pigment epithelium or RPE) and gradual loss of the light-sensitive photoreceptors in the macula. This type of AMD is called ‘dry’ macular degeneration because there is no leakage of fluid or blood. Over time, the disease may worsen, ultimately causing loss of most or all macular photoreceptor and RPE cells. This is known as geographic atrophy, and can be considered the end stage of dry AMD. Although there is currently no treatment for dry macular degeneration, diet and lifestyle, including the use of an appropriate supplement, can help slow disease progression and vision loss.
Retina Dry AMD
The wet form is characterised by a sudden loss of vision and is caused by abnormal blood vessels growing under the macula, followed by leakage and bleeding from these abnormal vessels. When wet macular degeneration develops early diagnosis and treatment are essential if severe permanent vision loss is to be prevented. There are a number of treatments available for wet macular degeneration. While these treatments cannot cure the disease, they aim to stabilise and maintain the best vision for as long as possible. In some people, treatment can improve vision.
The causes of MD are not fully understood but certain risk factors have been identified in the development of the disease:
Genetics: At least 70% of cases of macular degeneration have a genetic component, and it is estimated that people with a direct family history of macular degeneration have a 50% chance of developing the disease themselves. It is therefore important that people diagnosed with macular degeneration inform their siblings and children, since they are at increased risk and may benefit from screening.
Age: This is the main risk factor for developing AMD. As you get older your risk of developing the condition increases.
Smoking: A number of studies including the Blue Mountains Eye Study have shown a link between smoking and the development of AMD. Smoking increases our chances of developing macular degeneration by a factor of three. Studies have also shown that smokers develop macular degeneration around ten years earlier than non-smokers.
Nutrition: Nutrition plays an important role in optimising macular health and reducing the risk of macular degeneration. A healthy, well-balanced diet, which includes eye health foods, is good for overall wellbeing as well as eye health. For some people a supplement should also be considered.
Blood pressure: Some studies have shown that patients with high blood pressure have an increased risk of AMD. Exercising regularly and controlling weight can be beneficial for blood pressure and for overall health.
Sunlight: The cells of the macula are highly sensitive to UV light, and cell damage from sunlight can lead to worsening of AMD. The link between macular degeneration and sunlight exposure is not strong but protecting the eyes from UV light is recommended. This also makes going outside more comfortable for people with macular degeneration who are more sensitive to glare. The eyes can be protected by wearing a hat, sunglasses or transition lenses when outdoors.
Gender: women are more susceptible to AMD than men.
Common symptoms of AMD include:
- blurred vision
- distortion of objects and straight lines
- a dark patch in central vision
- objects appearing the wrong size, shape or colour
- difficulty seeing in bright sunlight and low light
- objects moving in and out of vision or disappearing
A comprehensive eye examination will be performed and may include testing of visual acuity, slitlamp examination by your ophthalmologist, wide-field retinal photography (Optos), optical coherence tomography (OCT), fluorescent angiography (FFA) and ICG angiography (ICGA). The results of the examination and investigations will allow your ophthalmologist to diagnose your eye condition and advise on management.
Early detection of macular degeneration is critical so that treatment can be initiated early. The type of macular degeneration you have will determine the treatment options recommended by your ophthalmologist.
Wet Macular Degeneration: There are a number of medical treatments available for wet macular degeneration.
Anti-VEGF injections into the eye are the most recent and most successful treatment for wet age-related macular degeneration (AMD). Clinical trials have shown that the use of anti-VEGF drugs maintains vision in the vast majority of wet macular degeneration patients.
Anti-VEGF injections work by blocking VEGF (vascular endothelial growth factor), a protein that stimulates formation of new blood vessels. This means that the anti-VEGF injections inhibit the growth of abnormal new blood vessels.
Anti-VEGF injection treatments can help to slow the visual loss and in some cases may improve sight.
The treatment regimen for macular degeneration usually begins with monthly injections for three months. Then, to control the disease, injections are typically continued on an indefinite basis. The interval between ongoing injections is determined by the ophthalmologist in consultation with the patient.
Currently there is no proven treatment to reverse vision loss from dry AMD. It is important to note that dry AMD can change into the wet form of the disease, and that any sudden change in vision requires prompt assessment by your eyecare professional.
While it is not possible to change your family history or age, it is possible to reduce the risk of macular degeneration or slow progression of the disease by making positive diet and lifestyle changes.
If you are a smoker then quit smoking.
A healthy, well-balanced diet, which includes eye health foods, is good for general as well as eye health.
The Macular Disease Foundation recommends adopting the following simple practices as a normal part of your diet. These practices can help reduce the risk of macular degeneration, whether or not you have been diagnosed with the disease:
- Limit the intake of fats and oils
- Eat dark green leafy vegetables and fresh fruit daily
- Eat fish two to three times a week
- Choose low glycemic index (low GI) carbohydrates instead of high GI. Low GI foods include most fruit and vegetables, whole grain cereals and whole grain breads and legumes
- Eat a handful of nuts a week
Links: Macular Disease Foundation: http://www.mdfoundation.com.au/