Understanding Macular Degeneration
What is the macula?Light passes through the pupil of the eye to be focused by the lens onto the light sensitive membrane at the back of the eye called the retina. The macula is a small area at the very centre of the retina. All parts of the retina contribute to sight, but it is the macula that allows us to see fine detail such as reading and writing, as well as our ability to see colour.
What is macular degeneration?Sometimes the delicate cells of the macula become damaged and stop working. There are many different conditions which can cause this. If it occurs later in life it is called Age-related Macular Degeneration. Macular degeneration is one of the main causes of visual loss in the elderly.
The two most common types of macular degeneration are Dry (Atrophic) Macular Degeneration and Wet (Exudative) Macular Degeneration. The terms wet and dry are not a description of how the eye feels, rather they describe what your ophthalmologist can see when looking at your macula.
Dry Macular DegenerationMost people have dry macular degeneration. It is caused by ageing and thinning of the tissues of the macula. Your ophthalmologist sees a collection of yellow, fatty deposits in the macula called drusen. Vision loss is usually gradual, with fading of colours and difficulty with reading. There may be a blank patch or dark spot in the centre of your sight.
Wet Macular DegenerationThis accounts for about 10% of cases of macular degeneration. It is caused by abnormal blood vessels developing at the back of the eye. These new blood vessels leak fluid or blood. Your vision may become blurred or distorted with objects appearing to have an unusual size or shape and straight lines appearing wavy or fuzzy. Vision loss may be rapid and severe.
The risk factorsThe cause of macular degeneration is still unknown.
The main clinically proven risk factor is smoking. Other possible risk factors include: genetics, sun exposure, light coloured irises, high blood pressure, cardiovascular disease, elevated blood lipids and a diet low in certain vitamins, minerals and anti- oxidants.
How is macular degeneration diagnosed?Your ophthalmologist may use a number of different methods to diagnose macular degeneration including: looking at the macula with special instruments, a simple vision test using a grid to detect distortion of the vision and special photographs called fluorescein angiograms. In this test, a fluorescent dye is injected into a vein in your arm. A rapid series of photographs of the back of the eye are then taken with bright flashes of blue light. These photographs give an accurate map of the changes occurring in the macula and help your ophthalmologist decide what is the best treatment for you.
How is macular degeneration treated?Despite much ongoing medical research, there is no cure for macular degeneration. Stopping smoking and controlling blood pressure and blood lipids will help to prevent macular degeneration from occurring or getting worse.
What about vitamins?Studies have shown that cumulative exposure to sunlight and smoking cause oxidative damage to the macula. Antioxidants called carotenoids (particularly lutein and zeaxanthin) protect the macula by filtering out harmful blue light. Despite their importance, these carotenoids are not naturally produced by the body and must be derived from the diet. The best source of carotenoids is however not carrots but green leafy vegetables such as spinach. Antioxidant vitamin preparations that may help prevent damage from macular degeneration and improve retinal function if macular degeneration is already present are available from your pharmacist.
Monoclonal antibody treatmentThere is a medication which is an approved treatment for wet age-related macular degeneration in Australia. It is a monoclonal antibody fragment. Along with abnormal blood vessels, certain proteins are thought to play a role in causing AMD. This treatment targets these proteins, preventing them from causing further visual loss. A course of medication injections into the eye may help to improve or maintain your existing vision. This procedure is carried out in the doctor’s rooms and requires only a local anaesthetic.
What’s the good news?Despite advanced medical treatment, many people with macular degeneration will experience some loss of vision.
The good news is that you will never go blind from macular degeneration. It only affects central vision used for seeing fine objects, colour and reading. The peripheral vision is never affected.
Can I be helped to see better?You can be helped to remain independent by learning to use your side vision. Low vision services can help you find the best magnifiers and give advice and training on simple ways in which you can make use of your remaining vision. Ask your eye doctor about these services.
What research is going on?A great deal of research is being undertaken looking at the causes of macular degeneration and how to prevent it.
Testing your vision with the Amsler gridCheck your vision daily using the Amsler grid below.
1. Put on your reading glasses and, in good light, hold the grid at a comfortable reading distance.
2. Cover one eye and look directly at the centre dot with the other eye.
3. Note whether all of the lines of the grid are straight, or whether any areas are distorted, blurred or dark.
4. Repeat the procedure with the other eye.
5. If any areas of the grid look wavy, blurred or dark, report this to your ophthalmologist immediately.
Example of what to report to your ophthalmologist
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