Understanding Macular Disease
There are many types of macular disease, and all types of serious macular disease affect the central vision, making it difficult to read, watch TV, or see faces. This page explains macular disease in general, with some details about age-related macular degeneration in particular.
Thinking of a camera can help you understand macular disease. A camera lens focuses a picture onto a film inside the camera. In our eyes a similar thing happens, but the film is replaced by the retina.
The retina 'makes' the pictures of the world that we see, converting the light into electrical signals that are then sent on to the brain.
a doctor or optometrist looks into the retina can be seen.
The macula is the central area of the retina, shown in yellow. The arteries are red, and veins blue.
The central area of the retina is called the macula. The macula is special, as it is the the most sensitive part of the retina. It makes out the fine details of the things we look at, peoples' faces, bus numbers, reading and writing, and the letters on an optometrists chart.
Whenever we look at an object, the image focuses on the macula. If the macula is damaged all these things we see in fine detail are misty. The picture is still there but we cannot make out any of the detail.
The brain builds up details of what we see by moving the macula over an object again and again.
The very centre of the macula is the fovea, which is used for very detailed vision.
A healthy retina will produce a clear image, like a normal film in a camera. But in macular damage the image will not be clear. For example if the film was scratched in the middle, the 'scratch' would show up in the middle of the photograph like a black mark or smudge of ink, as illustrated below. This is similar to damage caused by macular disease such as age related macular degeneration or diabetic maculopathy... the surrounding retina is not as sensitive as the macula, and cannot detect details such as writing or peoples' faces.
Sadly, the damage cannot be repaired. Because the detail in pictures is lost by damage to the macula, no amount of change to your glasses can restore this detail. People with age related macular degeneration or diabetic maculopathy find it difficult to read, write and or recognise faces.
Healthy Macula: in a camera a film will detect a detailed image. When the film is developed this is turned into a clear picture. Similarly, a healthy retina will produce a clear image.
Macular disease: an image with a central blurred area
Macular damage, often due to age related macular degeneration ARMD
As above, the macula area of the retina is responsible for the sharpness and details of what we see, when it is damaged pictures loose all their detail. Because of this no amount of change to glasses can restore the sight so details can be seen normally.
So people with macular degeneration find it difficult to read, write and recognise faces. People with macular degeneration may be able to walk through a busy supermarket, but not be able to see the price tags on the food. Just like the camera if the centre of the film is damaged, it may not be possible to see a person's face in the centre of a photograph, but an outline of the person and the other people nearby can still be seen.
People with macular degeneration may recognise where they are by seeing things and places at the sides. (People without macular degeneration may find this difficult to understand!) .
The central vision is lost in severe macular degeneration See diagram
The commonest cause is ARMD, age-related macular disease. There are other types of macular disease, such as the group of Juvenile Macula Dystrophies, macula holes, Diabetic maculopathy, and epiretinal membranes. The commonest type is age-related macular degeneration (ARMD) is discussed here.
New spectacles may help a little, but it is important to make the best use of the remaining eyesight. There are two ways to do this:
Looking sideways can bring people or objects or words into view.
To make the most of the peripheral vision ....the side vision.... you need to hold your head in an unusual position to so that whatever you are looking at is imaged (in the eye itself) at the side of the macula, under, or above it, on the healthy area of the retina. Experiment to find the best viewing angle.
Most people who have macular degeneration find that they automatically do this. It is unusual for this technique to be taught, it is solely a matter of moving the head to obtain the best possible vision. This technique occurs naturally as the disease progresses. It may be necessary to learn the technique when looking at details, such as peoples' faces.
By looking to one side the image
on the retina moves from the damaged macula on to the healthy
(Though this area of healthy retina does not see in detail, so the
image will appear blurred.)
Reading is difficult with severe macular degeneration, but is slightly easier magnifying the writing and looking to one side
Magnifying an object or words being read seems the obvious answer: if the object is bigger it can be seen by the part of the retina outside the damaged area. Remember the person who can see to get about in the supermarket... the sight at the sides is normal.
There is a problem. When looking through a magnifier the field of view is small, so only a few words can be seen at one time. To overcome this you need to move the magnifier along the line to 'piece the sentence' together. This takes a lot of practice: you have to move your eyes along the line, whilst trying to use the side vision, whilst looking through a magnifying glass, trying to guess missing sections of words. Reading is still possible even with medium size print, although it is usually very slow.
hallucinations are common in macular disease
Many people with poor sight notice hallucinations. Such hallucinations are very common in macular degeneration. These can take various forms, and are described in more details in the BMJ here, and here. They can occur if your sight is patchy: if your sight is poor on one side for instance, you may notice the hallucination on that side.
For help see and join the Charles Bonnet Syndrome Organisation Esme's Umbrella
Sometimes the hallucinations are frightening, and can even take the form of animals or people. If you see such things that are not really there, you are not going mad...it is quite normal if you have poor sight. If they are very disturbing discuss them with your doctor or ophthalmologist.
Proton pump inhibitor drugs can increase hallucinations IOVS 2013. These are used to treat stomach/indigestion problems.