Age Related Macular Degeneration (AMD) occurs with advancing age and is caused by inflammation and photo-oxidative stress in patients over the age of 50. Genetic predisposition, smoking and high blood pressure are significant risk factors.
Although AMD reduces vision in the central part of the retina it does not affect the side or peripheral vision. Therefore AMD alone does not result in total blindness. Even in more advanced cases people maintain very useful vision. In many cases, macular degeneration has a minimal impact on lifestyle.
There are two forms of macular degeneration, “dry” AMD and “wet” AMD. A person can suffer from both forms, and it can advance slowly or rapidly in one or both eyes. Dry AMD can progress without turning into wet AMD, however in some cases dry AMD can change rapidly into wet AMD.
Dry Macular Degeneration: This is the most common form of AMD and accounts for 85-90% of cases. It is caused by ageing and thinning of the macular tissues and usually results in a slow loss of vision. One of the early signs of dry AMD is yellow deposits under the retina called drusen. Drusen alone do not cause vision loss but when they increase in size or number it generally indicates an increased risk of developing advanced AMD. Smaller drusen may not cause symptoms however your ophthalmologist can detect drusen during a dilated eye examination.
Wet Macular Degeneration: Wet AMD is much less common, approximately 10% of cases. It occurs when new blood vessels grow beneath the retina. These blood vessels tend to be fragile and often leak fluid or bleed into the macula and surrounding areas resulting in scarring of the macula. When this happens, the loss of vision occurs rapidly and is often quite severe.
Wet AMD is sometimes called ‘exudative’ AMD (exudates are areas of leaked fluid) or ‘neovascular’ AMD (neovascular means new blood vessel growth).
An early symptom of wet AMD is distorsion, straight lines appear wavy, and this can be detected on an Amsler Grid. If you notice this contact your the eye clinic immediately for a comprehensive dilated eye exam.
Although the exact cause of AMD is unknown, the main risk factors appear to include:
- Increasing age
- A family history of AMD
Many people do not realise that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist can detect early stages of AMD during a comprehensive eye examination that includes the following:
- Amsler Grid – A simple vision test in which you look at a chart that resembles grid paper (Amsler Grid).
- Colour vision test.
- Viewing the macula with an ophthalmoscope.
- Fluorescein Angiography – a special camera is used to take photographs of the macula.
- OCT (Optical Coherence Tomography) – a non-contact, non-invasive imaging technique used to obtain high resolution cross-sectional images of the macula.
- Blurred vision
- Wavy vision (straight lines look wavy)
- Gray or black areas in the visual field
- Loss of colour perception
It is important to note that the current treatment of AMD does not cure the disease but aims to stabilise the disease process and maintain the best vision for as long as possible.
Nutritional Supplements – Antioxidant vitamins and zinc may reduce the impact of AMD in some people. Vitamin supplements are not a cure for AMD, nor will they restore vision. However specific amounts of these supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision. You should speak to your ophthalmologist to determine if you are at risk of developing advanced AMD and if supplements are recommended for you.
Laser Treatment – Certain types of wet AMD can be treated with laser. A high energy beam of light is used to seal leaking blood vessels and destroy abnormal blood vessels. However, laser treatment may also destroy some of the surrounding healthy tissue and some vision. Laser is more effective when the abnormal blood vessels have developed away from the fovea or central macula. The risk of developing new blood vessels after laser is high and repeated treatments may be necessary. In some cases vision loss may still progress despite repeated laser treatment.
Photodynamic Therapy – Photodynamic Therapy (PDT) is a treatment that has been shown to help slow the growth of abnormal blood vessels in patients with “wet” AMD. A light sensitive drug, called Visudyne, is injected into a vein in your arm. This drug flows through the blood vessels around your body including the abnormal blood vessels at the back of your eye. The drug will stick to the inside surface of the abnormal blood vessels. A non-thermal laser is then shone into your eye for 90 seconds. This laser activates the Visudyne. The activated drug destroys the abnormal blood vessels without damaging the surrounding healthy tissue.
PDT is relatively painless and can be done in the ophthalmologists rooms. It will slow the rate of vision loss, however it does not stop vision loss or restore vision in eyes already damaged. Results are often temporary and you may need repeat treatments. PDT may be used on its own or in combination with other therapies in special cases.
Anti-VEGF Treatment – A chemical in the body called vascular endothelial growth factor or VEGF, is critical for causing the growth of abnormal blood vessels under the retina. Recently scientists have developed different drugs (called anti-VEGF) that can block the VEGF. Blocking the VEGF reduces the growth of abnormal blood vessels, slows their leakage and helps to slow vision loss. The anti-VEGF drug must be injected into your eye with a very fine needle. Usually patients receive multiple anti-VEGF injections over a period of many months to help slow vision loss. As with any procedure there is a small risk of complications, usually resulting from the injection itself. For most people the benefit of the treatment outweighs the risk involved.
Details regarding risks and complications will be provided by your treating Ophthalmologist when discussing treatments and proceeding with consent. At this time, your Brisbane Eye Clinic Ophthalmologist will be pleased to answer any queries you may have.
It is possible to reduce the risk of developing AMD by:
- Ceasing Smoking
- Eating a diet rich fresh fruit and dark green leafy vegetables (spinach, brussel sprouts, broccoli) as well as brightly coloured fruit and vegetables (corn, capsicum, carrots)
- Increase intake of omega rich foods such as fish
- In consultation with your ophthalmologist supplement your diet with vitamins, minerals and antioxidants
- Control cholesterol and BP levels
- Check your eyes regularly for signs of AMD
Low vision optical aids help improve vision for people with macular degeneration. Spectacles, hand or stand magnifiers, telescopes, computers and closed circuit television are some of the available resources. Brighter illumination is also beneficial along with large print books and newspapers. With these devices, people with visual loss can usually read, do modified close work and take care of themselves.