Age-related Macular Degeneration
Age-related macular degeneration (MD) is the term we give to degenerative problems involving part of the retina at the back of the eye which we call the macula. The macula is important as it is responsible for our high quality central vision, and allows us to see fine details. MD usually affects people over 60 but occasionally happens earlier. The risk of developing MD increases with age and is much higher in people who smoke.
This form is quite common and 8 out of 10 of people who have MD have the dry form. With age, parts of the macula get thinner, becoming pale, and tiny clumps of debris called drusen accumulate under the retina. The rate of progression of dry MD varies and in most people it will develop only slowly. People with the dry condition are usually able to manage well visually for many years after its onset.
This variant of MD is less common but much more rapidly progressive than the dry form. Wet MD is the term we use when new and abnormal blood vessels grow under the retina in the macular area. It can be considered a complication of dry MD. These new vessels leak blood and other fluids, ultimately causing scarring of the macula.
Vision is lost faster with wet MD than with dry MD and it can develop very suddenly. Noticeable vision changes occur in a few days or weeks. Around 10 to 15 per cent of people with dry MD develop wet MD so if you have been diagnosed with the dry form of the disease and notice a sudden change in your vision, you should contact a specialist urgently. The commonest thing people notice about their vision when the wet form develops is distortion of the central vision – a symptom called ‘metamorphopsia’. The visual loss from wet MD can be reversed in many cases and early treatment improves the outcome.
What are the symptoms of MD?
MD affects people in different ways. Symptoms may develop slowly however, as the condition progresses, your ability to see clearly will change. Typical symptoms of MD include:
- Gaps or dark spots (like a smudge on glasses) may appear in your vision,
especially first thing in the morning.
- Objects in front of you might change shape, size or colour or seem to move or disappear.
- Colours can fade.
- You may find bright light glaring and uncomfortable or find it difficult to
adapt when moving between environments of different lighting intensity.
- Words might disappear when you are reading.
- Straight lines such as door frames and lampposts may appear distorted or bent.
Monitoring for MD
We often recommend people monitor their vision with what is called an ‘Amsler Grid’. This is simply a fine grid of squares with a central fixation spot. Ordinary graph paper can serve the same purpose. Metamorphopsia becomes obvious as distortion in the lines of the grid. Regular weekly checks of the vision of each eye individually using the grid can help to detect early wet MD.
At this time there is no way to treat the dry form of MD. However, people with a lot of drusen might benefit from taking a certain combination of nutritional supplements. Our retinal specialists can tell you if vitamins and minerals are recommended for your dry MD.
Medications called ‘anti-VEGF’ drugs are used to treat wet MD. Anti-VEGF treatment helps reduce the number of abnormal blood vessels in the macula. It also slows the leaking from blood vessels. This type of medication is delivered into the eye by intravitreal injection through a very slender needle. Treatment regimes are tailored to each individual situation but the commonest approach is what is called the ‘treat and extend’ model. This involves three initial injections at one month intervals, followed by a graduated increase in intervals of the subsequent maintenance injections to 3 monthly – depending on the response to treatment. It is often possible to stop treatment eventually, but some people will require maintenance injections indefinitely.