Macular Degeneration is the leading cause of visual loss in over 60 year olds. It affects only central vision so there are difficulties with reading, driving and other fine, detailed visual activities.
How the Eye Works
The eye functions like a camera with a lens system at the front of the eye focusing light on the retina, the light-sensitive layer lining the inside back of the eye wall.
The central part of the retina is called the macula. If the retina is likened to a dartboard, the macula is the bull’s eye. The macula is the most sensitive area of retina and gives you central vision. Central vision is sharp and detailed allowing you to read, recognize faces and drive.
The peripheral retina, surrounding the macula, is for side vision. It is less sensitive and only makes coarse visual distinctions but enables you to move about easily.
What is Macular Degeneration?
Macular Degeneration is a type of macula damage with progressive breakdown of the macular tissue.
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. Colour may be altered.
Loss of vision usually starts slowly only in one eye and then later affects the other eye. 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 well. 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 macular degeneration affects only the centre of vision and never leads to complete blindness.
Types of Macular Degeneration
There are two main types of macular degeneration, a dry and a wet type.
1. Dry Macular Degeneration:
90% of people with macular degeneration have this form. The light-sensitive cells of the macula gradually break down. There is slow loss of central vision which is usually mild to moderate and often begins earlier in one eye.
Some cases of 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 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 fluid or bleed. When this occurs, vision suddenly worsens. As treatment must be given promptly, it is most important to monitor vision in each eye regularly and report any change in vision.
Diet and Vitamin Supplements
People with a diet high in fruits, nuts, fish oils and vegetables (especially leafy, dark green vegetables) and low in red meat are less likely to have macular degeneration. Smoking is also a serious risk for visual loss.
Taking supplements such as vitamins C and E, beta-carotene (not to be used by smokers or ex-smokers) and zinc may lower the chances that macular degeneration will get worse in some patients. Therefore, many patients with macular degeneration should consider taking supplements. More research needs to be done on this subject and supplements are not recommended for all patients.
Treatment of Wet Macular Degeneration
Monitoring Your Vision
You need to be on the lookout for any change in symptoms in central vision and to have a prompt 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.
Photodynamic therapy (PDT)
Photodynamic therapy may be used as an adjunct to treatment with Avastin or Lucentis for wet Macular Degeneration. A dye called Visudyne is injected into a vein in the arm and travels to the eye. 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 without damaging the overlying retina. Several treatments are usually needed over a 2-3 year period to completely destroy the abnormal blood vessels.
Avastin and Lucentis
Avastin and Lucentis are drugs that suppress the growth of abnormal vessels under the retina. The drug is injected into the eye. A course of 3 or more injections every 4-6 weeks will be needed. Treatment may be for a minimum of about 4 months but many need to continue 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.