What is Macular Degeneration?

The retina is the delicate layer of tissue that lines the inside wall of the back of the eye. The macula is a very small area in the center of the retina. This small area is responsible for our central "straight ahead" sight used for reading and other fine tasks.

As the eye looks straight ahead; the macula is the point of the retina upon which the light rays meet as they are focused by the cornea and the lens of the eye. Similar to the film in a camera, the retina receives the images that come through the "camera-like" lens. If the macula is damaged, the central part of the image is blocked as if a blurred area had been placed in the centre of the picture. The image around the blurred area may be clearly visible.

Macular degeneration is damage or breakdown of the macula. The eye still sees the objects to the side, since side, or "peripheral", vision is usually not affected. For this reason, macular degeneration does not result in total blindness. However, it can make reading or close work difficult or impossible without the use of special low vision optical aids.

Although macular degeneration most often occurs in older people, aging alone does not always result in central visual loss. Nevertheless, macular degeneration is the leading cause of impairment of reading and fine "close-up" vision in Australia.

TYPES AND SYMPTOMS

The most common form of macular degeneration is called involutional (senile) macular degeneration. This form accounts for 70% of all cases, and is associated with aging. It is caused by a breakdown or thinning of the tissues in the macula.

About 10% of macular degeneration falls into a category called exudative macular degeneration. Normally the macula is protected by a thin tissue that separates it from very fine blood vessels nourishing the back of the eye. Sometimes these blood vessels break or leak and cause scar tissue to form. This often leads to the growth of new abnormal blood vessels in the scar tissue.

These newly formed vessels are especially fragile. They rupture easily and may leak. Blood and leaking fluid destroys the macula and causes further scarring. Vision becomes distorted and blurred, and dense scar tissue blocks out central vision to a severe degree.

Other types of macular degeneration are inherited and not associated with the aging process. Occasionally injury, infection or inflammation may also damage the delicate tissue of the macula.

If only one eye is affected, macular degeneration is hardly noticeable in the beginning stages, particularly when the other eye is normal. This condition often involves one eye at a time, so it may be some time before a patient notices visual problems.

Macular degeneration can cause different symptoms in different people. Sometimes only one eye loses vision while the other eye continues to see well for many years. If both eyes are affected however, reading and close-up work may become extremely difficult. Macular degeneration does not cause blindness. Since side vision remains, people can usually take care of themselves quite well.

Colour vision may become dim and these other visual symptoms can develop due to macular degeneration.

Words on a page look blurry.

Straight lines look distorted, and in some cases the centre vision looks more distorted than the rest of the scene.

A dark or empty area appears in the centre of vision.

DETECTION AND DIAGNOSIS

Many patients do not realise they have macular problem until blurred vision becomes obvious. An ophthalmologist can detect macular degeneration in the early stages. The ophthalmologist examines the macula carefully by viewing it with an instrument called an ophthalmoscope to see if damage is present.

The examination will usually include a few more tests:

• A grid test, in which the patient looks at a test page (similar to graph paper), will be used to check for the extent of sight loss spots.
• A colour vision test will show whether a patient can tell colour differences, and additional tests will help to discover conditions that may be causing the macula to deteriorate. * Sometimes a fluorescein angiogram is done. The ophthalmologist injects a dye into the patient's arm, and then takes photos of the retina and macula. The dye helps to clarify any blood vessel abnormality that might be present. Macular degeneration can be detected and diagnosed early by an ophthalmologist if periodic eye exams are part of health care. Early detection is important, since people may not realise their vision is impaired. Having your eyes checked is especially appropriate if other family members have a history of retinal problems. For patients with macular degeneration, early diagnosis by an ophthalmologist may prevent further damage, or aid the individual to make a visual adjustment with low vision aids.

While covering one eye, look at the centre of the grid. If the lines around the dot are wavy or distorted, you may have a macular problem.

MEDICAL AND SURGICAL TREATMENT

There is no cure for the most common involutional form of macular degeneration. However, the laser has been used to retard the spread of the less common exudative form, but only if this treatment is applied in the very early stages of the condition. In this treatment a focused intense beam of laser light is used to seal off leaking membranes and destroy new blood vessels. This reduces further loss of vision from progressive scarring of the macula and the surrounding retina.

There is much research work being pursued to find ways of preventing and treating Macular Degeneration. Several new methods of treatment have shown promise and may help to find answers in the future.

WHO CAN TREAT MACULAR DEGENERATION?

Only an ophthalmologist can treat macular degeneration. An ophthalmologist is a medical doctor who is educated, trained and licensed to provide total care of the eyes. This care includes performing comprehensive eye examinations, prescribing corrective lenses, diagnosing diseases and disorders of the eye, and carrying out the medical and surgical procedures necessary for their treatment.

OPTICAL AIDS

Low vision optical aids help improve vision for people with macular degeneration. Many different types of magnifying devices are available. Spectacles, hand or stand magnifiers, telescopes and closed circuit television for viewing objects are some of the available resources. Aids are either prescribed by your ophthalmologist or by referral to a low vision specialist or centre. Special lamps with brighter illumination are often beneficial. Books, newspapers and other items available in large print offer further help.

A patient with macular degeneration can be helped. Fortunately, visual aids are available to assist patients in leading a comfortable and relatively normal life.

With these devices, people with visual loss can usually read, do modified close-up work and take care of themselves.

If you are over age 50, or if your family has a history of retinal problems, you should have your eyes checked periodically for signs of eye diseases like macular degeneration that occur in the older age group. Early detection and subsequent treatment, if indicated, may help prevent additional visual loss.

For further information contact your family doctor. If necessary, he will refer you to an ophthalmologist.