Eye Diseases - Macular Degeneration

What is age related macular degeneration or just "macular degeneration"?

This is a slowly progressive degeneration or "wear and tear" process affecting the macula. It is seen in older people and is related in some to smoking. Whilst a lot is known about how macular degeneration affects vision, very little is known about what causes macular degeneration. Rarely it is transmitted through families. There are some known genetic predisposing factors.

What happens in macular degeneration?

In the early stages, deposits of metabolic debris, known as "drusen" form in or under the retinal pigment epithelium. (This links to diagram of the retinal anatomy). Many people with drusen do not experience any change in their vision.

What you can do to prevent macular degeneration?

• If you are a smoker, work toward giving up smoking.
• Eat leafy, green vegetables. Recommended are:
• Spinach, bok choy, broccoli, leek, capsicum, sweet corn, silver beet, turnip greens.
• Eat good quality nuts, especially almonds. Also, unroasted brazil nuts, walnuts, pine nuts.
• Eat two fish meals a week, preferably with some salmon in one. Tinned sardines and tuna are good sources of Omega 3 fatty acids.
• Eat a low fat diet and make sure the fats are “good” ones. Avoid all deep fried food, palm oil, potato crisps. Pan fry or grill meat. Use virgin olive oil for cooking.
• Eat a low glycaemic index diet. This means eating foods that don’t give you a quick sugar “fix” but which keep you from feeling hungry for longer periods. For instance, chocolate is a high glycaemic index food which will fill you up for 30 minutes but soon you will feel hungry again. Muesli is mostly low glycaemic index so long as it is not toasted in bad fats, or coated in sugar or honey. 
• Use the AREDS vitamin supplements for zinc and antioxidants. These can be obtained in the preparation known as “Macuvision”.
• Consider using another supplement currently under study. “Luteinvision” contains the macular pigments lutein and zeaxanthine.
• Monitor your vision with the Amsler grid on a weekly basis. Report any sudden change in vision to your eye doctor promptly.
• Have periodic eye examinations by an eye health practitioner skilled in diagnosis of macular degeneration.

Different types of drusen (deposits of metabolic debris)

There are at least 4 different types of drusen: hard, soft, semisolid, and regressing.

• Hard drusen can sometimes occur even in younger people and can even be inherited rarely. Hard drusen often mean that vision will remain good for a prolonged period.
• Soft drusen on the other hand do imply that vision may be affected in the future, either by elevation of the macula or by bleeding (wet macular degeneration).
• Regressing drusen usually are the forerunners of dry macular degeneration in which the retinal cells simply melt away.

Many people have drusen for years without problems. Some people will progress onto the dry form of macular degeneration in which the macular tissue dissolves (like the silvering coming off the back of a mirror). This is the most common form of macular degeneration. It causes a very slowly progressive loss of reading vision. At first, a letter or word may be missing when reading, followed by increasing problems with print, and eventually reading may become impossible other than with the aid of magnification. This process often takes years.

In the worst cases, reading vision may be lost completely. Also the ability to drive, watch TV, or even recognise faces may be lost. However, side vision remains so that the person with dry macular degeneration will be able to walk about without assistance. They are not blind in the full sense of the word.

For some people soft drusen can blend together or "coalesce" to make a broad area of elevated pigment epithelium and retina. Vision is usually blurred and distorted by this process but these lesions may remain stable for quite some time. Eventually however, they may convert either to the wet form of macular degeneration with bleeding or to the dry form.

Wet Macular Degeneration

In a small percentage of cases, macular degeneration can take the form of bleeding or exudation. This is "wet" macular degeneraton. Typically, relatively sudden blurring of vision occurs in one eye, often accompanied by distortion of vision with straight lines appearing bent, broken or curved.

In wet macular degeneration abnormal capillaries ("new vessels") from the choroid grow under the retinal pigment epithelium or retina. These capillaries are fragile and leak or bleed. Serum and blood collect under the retina and affect the processing of light. Eventually the new vessels form a fibrous scar and vision becomes poor.

Treatment of Macular Degeneration

There is no cure for age related macular degeneration (AMD) but this condition can be treated in some instances and occasionally prevented to a certain extent.

The most important consideration is establishing an accurate diagnosis - see an eye doctor about this. Other eye problems that affect vision need to be detected and treated. An up to date glasses prescription is important. Cataracts and glaucoma should be treated. There is now a well established link between smoking and AMD so it makes good sense to avoid or give up smoking. Dry AMD is still not treatable. Wet AMD is treated by a series of injections (Lucentis, Avastin).

The dry form of AMD is the most common and least treatable. There is no way of halting the progressive degeneration of the retina in this condition. Various types of magnification devices can be used in conjunction with glasses to enhance reading. Advice on these can be obtained from the Vision Australia.  A very useful closed circuit TV device known as "Smartview" is excellent for reading and is available from Pulsedata company or Humanware company. People with dry AMD should take a specific vitamin supplement and adhere to dietary principles.

Wet AMD is caused by growth of abnormal blood vessels from the choroid layer under the retina. This affects vision by causing leakage or bleeding under the macula, by physically distorting the macula, or by scarring the macula.

Wet AMD accounts for less than 20% of all AMD cases but causes 90% of severe visual loss and frequently affects both eyes (risk varies from 7% to 87% depending on individual characteristics). In addition, the dry form of AMD can become wet in 10-20% of cases.

When the abnormal blood vessels grow under the macula ("subfoveal new vessels") then most affected eyes will have poor central vision (<6/60) within 2 years if left untreated. In the past, various treatments have been used including laser, radiation, and photodynamic therapy. These have now been superseded by the much more effective technique involving injection of Lucentis or Avastin into the eyeball.

Lucentis and Avastin Treatment

These two drugs are very similar and equally effective. They work by inhibiting the growth of new vessels and reducing their tendency to leak or bleed. They do this by blocking a protein known as “VEGF”. The injections are given at monthly intervals initially and then customised depending on response. The injections are done in the office with local anaesthesia and cause very little discomfort. Response to treatment is monitored by OCT scanning or fluorescein angiography. These drugs have become the mainstay of treatment and work extremely well.

Conventional laser treatment for wet AMD is still used occasionally.  In certain cases, where a new blood vessel has grown under the retina and is bleeding or leaking, laser treatment can be used to cauterise the blood vessel and prevent further loss of vision. It is only in early cases that this is applicable and certainly it is not available for the majority of people. This type of laser does damage the retina itself and will always leave a "blind spot" near or even involving the centre of vision. The main problem with this type of treatment is that the new blood vessels tend to regrow in up to 50% of cases within the first 6-12 months.

Macular translocation surgery.

Another therapy which is still in its infancy involves the use of retinal surgery to move the macula away from a leaking blood vessel such that conventional laser treatment can be used without direct harm to the macula itself. Naturally this is an invasive procedure with a real risk of surgical complications. Its usefulness has not been established in any trials and the technique is undergoing constant refinement. However, in appropriate cases, particularly where the other eye has already gone blind from ARMD, this may be a beneficial approach. However, it is no longer widely practiced due to the use of Lucentis.

Surgery for massive haemorrhage - Occasionally wet ARMD can progress to large blood clots under the retina or in the vitreous cavity or both. In selected cases blood clots can be moved away from the macula with some benefit to eyesight. Blood in the vitreous cavity can be cleared by a standard vitrectomy operation.

Microchip implants - Experimental work continues in this area and in time it may be a treatment modality.

Eyeball transplants - This is an impossible treatment at this time.

Finally, what is done when nothing can be done?

Low vision aids are important and the services of Vision Australia, Retina Australia support group, and Guide Dogs Association should be sought. For those people who have vision of less than 6/60 in both eyes, the Blind Disability pension is available and is not means tested. Vision Australia can advise you on this.