What is Macular Degeneration (MD)?
Macular degeneration (MD), also known as age-related maculopathy or senile macular degeneration, is damage or breakdown of the macula. The macula is a very small part of the retina, the light-sensitive
tissue of the eye, which is responsible for central vision. This is the part of the retina that is used for the finest detailed vision.
How does MD affect vision?
MD damages the part of the retina responsible for central vision
and for seeing fine detail, and makes it difficult to see small details of objects. Side vision is not affected. If both eyes are affected, reading and other tasks requiring fine vision may become very difficult, but because side vision remains, people with
MD can usually take care of themselves.
What causes MD?
MD is the result of ageing processes in the eye. Some of the layers of the retina thicken and waste material which is usually removed from the retina forms deposits, distorting
the retina. This distortion can cause damage to the other layers of the retina. In about 10 per cent of cases, new blood vessels grow into the macula from beneath. These newly-formed (neovascular) vessels are fragile and often leak blood into the retina, where
the blood causes scar tissue to form. The scarring severely blocks central vision. Other forms of macular degeneration are inherited and not associated with ageing.
How common is MD?
Macular degeneration is the major cause of
vision impairment and blindness in Australia for people over the age of 50. Early MD occurs in about 14% of those aged 55 to 64 years, 18% of those aged 65 to 74 years, and 30% of those aged over 75 years. Men and women are equally affected. MD accounts for
almost 50% of legal blindness and up to 70% of seriously impaired vision in people over the age of 70 years.
How is MD detected and diagnosed?
People with MD may notice that they can no longer read as quickly as previously even
with their reading glasses, or they may notice that their vision has deteriorated. Many patients do not realize that they have a problem until their vision becomes blurred. Optometrists perform a number of tests in an examination, which enable them to detect
the presence of MD in the early stages.
The optometrist examines the macula carefully with a range of specialized instruments such as an ophthalmoscope, retinal camera or slit-lamp with a high-powered lens. These instruments allow examination
of the interior of the eye, including the macula. Sometimes the optometrist may place a drop in the eye to dilate the pupil to get a better view of the internal structures. Through the ophthalmoscope the optometrist will look for changes in the macula, such
as accumulation of waste material or new blood vessels.
Another test that may be used is a grid pattern known as an Amsler chart. This is a regular grid that looks like a piece of graph paper. Patients with MD often report that sections of the grid
appear to be distorted or missing.
Optometrists will usually refer patients whom they suspect have MD to an ophthalmologist (eye surgeon) for confirmation of the diagnosis. The ophthalmologist may perform a test called fluorescein angiography. In this
test a fluorescent dye is injected into the patient’s bloodstream and the ophthalmologist observes the progress of the dye through the blood vessels in the retina. This reveals any leaking blood vessels.
Can MD be treated?
Recent advances in treatment of the early stages of neovascular MD involve injection of anti-VEGF (vascular endothelial growth factor) substances that prevent the formation and growth of abnormal blood vessels. This is the first treatment of MD that has
been shown to improve vision in some cases but complete or permanent resolution of abnormal blood vessels is not possible. The treatment needs to be repeated as part of ongoing management of the disease. Associated risks of anti-VEGF treatment include formation
of cataract and ocular inflammation.
Photodynamic therapy (PDT) is a well-established treatment for vascular forms of MD. Laser surgery may be used where new blood vessels have appeared in the macula area. A focused, intense beam of laser light is used
to seal leaking blood vessels and prevent new vessels growing. This treatment is most effective when it is applied in the very early stages of the disease, before extensive damage has been done.
There is little that can be done to cure MD, particularly
in its more advanced stages. One study found that antioxidant vitamin and mineral supplementation assisted in halting the progression of MD in a small percentage of patients. These supplements should be taken under the supervision of a health care professional
as they may be associated with harmful effects.
People with MD can be helped to continue functioning normally. Many will eventually be classified as having low vision. Help in the form of low vision devices is available from optometrists and specialist
low vision clinics. Low vision devices enable patients to make the most of their vision and include miniature telescopes, high-powered reading spectacles, hand-held and stand magnifiers, closed circuit televisions and other simpler aids such as large-print
What should you do about MD?
For treatment of MD to be effective, it must be diagnosed as early as possible. Regular eye examinations are the key to early detection of retinal changes and other signs of disease. If you
notice any change in the quality of your vision, have your eyes examined immediately. Regular examinations are particularly important for people over the age of 50 years and people whose families have a history of eye problems. Other important preventative
measures include minimizing exposure to UV light and cigarette smoke, both of which are associated with MD. A low-fat diet rich in green leafy vegetables, nuts and fish may be beneficial in reducing the impact of MD.