Macular degeneration is the leading cause of visual loss in over 60 year olds. It only affects central vision so difficulties are usually found with reading, driving and other daily activities that require fine detailed central vision. Complete blindness does not occur.
What is Macular Degeneration?
Macular Degeneration is a type of macula damage fairly common later in life, affecting some 6% of people aged 60-75 years and 20% of those over 75 years.
The onset is a disturbance of the centre of vision. This ranges from a blur or distortion to a blind spot. Objects may appear distorted, larger or smaller or simply different. Distortion is waviness of straight lines such as a ruler's edge or a power pole. Colour may be altered.
Loss of vision usually starts only in one eye. Later is usually affects the other eye but this is not always the case. If only one eye is affected, early changes may be difficult to detect in day-to-day life because the healthy eye can still see detail. In most instances macular degeneration progresses rather slowly. Only rarely does vision deteriorate rapidly.
It is only when both eyes are severely affected that detailed vision will become very difficult. Even with severe macular degeneration of both eyes, peripheral vision is still intact and enough vision is retained to enable many tasks to be continued. Almost all people with severe macula degeneration in both eyes can see well enough to take care of themselves and continue with activities that do not require detailed vision. It is very important to understand that age-related macular degeneration never leads to complete blindness. Only the centre of vision is affected, peripheral vision is preserved.
Types of Macular Degeneration
There are two main forms of macular degeneration, a dry form and a wet form.
1. Dry Macular Degeneration: Ninety percent of people with macular degeneration have this form which may lead to slow and progressive loss of central vision. The light-sensitive cells of the macula gradually break down, often beginning earlier in one eye. Antioxidant therapy and probably some modifications to diet and other aspects of lifestyle that may help to slow progression of some forms of dry macular degeneration (see later). Otherwise, there is no medical or surgical treatment for this form of macular degeneration. If there is significant deterioration of vision, low vision aids such as magnifying lenses for near vision and telescopic lenses for distance vision are often helpful. With time, it is sometimes possible to learn to use the more peripheral vision for coping with day-to-day tasks.
In a small proportion of cases dry macular degeneration changes to the wet form. As the wet form can sometimes be treated it is important for patients with the dry form to regularly monitor their vision and report any changes.
2. Wet Macular Degeneration: This form occurs in 10% of cases but accounts for 90% of cases of severe central visual loss.. Abnormal blood vessels grow under the retina and may leak fluids or bleed. When this occurs, vision suddenly worsens. In some cases, prompt laser treatment with argon laser or photodynamic therapy may halt or even improve visual loss. However, even if treatment is initially successful, visual loss may occur at a later time. As treatment must be given promptly, it is most important to monitor vision in each eye regularly and report any change in vision.
Monitoring Your Vision
You need to be on the look out for any change in symptoms in central vision and to have an examination if any change occurs.
Blurred vision- the change may be small - a blurred spot in the centre
Distortion-straight lines become wavy
Change in the size of an object in the central vision-bigger or smaller.
Normal Amsler Grid Abnormal Amsler Grid
This is a simple yet sensitive method for detecting change in your central vision. It is easy to do at home and is used to regularly monitor your central vision. If a change is found you need to be reassessed promptly.
An abnormality is detected by looking at a grid of lines. Any deviation from a normal appearance indicates abnormality. For monitoring vision at home any alteration in the appearance of the grid needs to be reassessed by your ophthalmologist. The test is usually done weekly.
If there is any suspicion of the wet form of macular degeneration, then a fluorescein angiography test is usually indicated. Dye is injected into a vein in the arm. A series of photographs is taken of the retina as the dye passes through the blood vessels of the eye. The photographs show far more details of the disease and may provide enough information to plan treatment of the abnormal blood vessels.
Optical Coherence Tomography (OCT)
OCT is an imaging technique using light to give detailed cross-sectional images of the retina. In macular degeneration the image allows for very accurate assessment of whether there is wet macular degeneration present. It is very useful for monitoring treatment of wet macular degeneration.
Normal macular OCT scan Wet macular degeneration with fluid (black spaces) within the retina
Diet and Vitamin Supplements
People with a diet high in fruits and vegetables (especially leafy, dark green vegetables) are less likely to have macular degeneration. Taking supplements such as vitamins C and E and zinc may lower the chances that macular degeneration will get worse in some patients. Therefore, many patients with macular degeneration should consider taking antioxidant and zinc supplements. Supplements are not recommended for all patients.
For more information see page on Diet and Supplements.
Treatment of Wet Macular Degeneration
In a small number of cases where there is growth of abnormal blood vessels under the retina. Without treatment there is loss of central vision. Treatment may be possible and aims to stabilize central vision. A fluorescein angiogram is required to assess treatment possibilities.
1. Avastin and Lucentis
These ' anti-VEGF' drugs suppress the growth of abnormal vessels under the retina. The drug is injected into the eye. A course of injections every 4 - 6 weeks for at least three or more treatments will be needed. Treatment may be for a minimum of about 6 months but many need to be continued for two or more years. These drugs are very effective and the first line treatment. All other treatments are alternatives if there is an incomplete response.
2. Photodynamic therapy (PDT)
PDT may be used as an adjunct treatment with Avastin or Lucentis. A drug called Visudyne is injected via a vein in the arm to travel to the eye where it adheres to the abnormal vessels under the retina. The retina is then exposed to a low energy laser beam that selectively destroys the abnormal vessels. Persistence of the abnormal vessels is fairly common and more than one treatment are usually needed.