Acting against AMD

Going for regular eye examinations and eating the right foods are the key to preventing loss of eyesight from this common condition.

WOULD you rather lose your eyesight or a limb? How about giving up 10 years of your life in exchange for your eyesight?

If you would rather lose a limb or 10 years of your life than go blind, you are not alone.

A recent international survey by eye healthcare company Bausch + Lomb found that two-thirds of the 11,000 respondents from 11 countries around the world would rather shorten their lives by 10 years than to lose their eyesight.

The results of the survey called Barometer of Global Eye Health announced last month, also revealed that 68% preferred to lose their limbs rather than their sight, while 78% would rather give up their hearing, and 79%, their sense of taste.

Despite that, the survey found that less than one-third of respondents take the necessary steps to preserve their eyesight, with only 21% having gone for regular eye examinations over the past five years.

And the reason given by 65% of those respondents who do not examine their eyes regularly for not going for these check-ups is that they did not have any eye symptoms.

However, this is a dangerous line of reasoning, as many eye diseases can develop quite extensively without any obvious symptoms.

One of these diseases is age-related macular degeneration (AMD).

How we see

According to consultant ophthalmologist Dr Kenneth Fong, AMD is the leading cause of blindness in people aged above 60 years in the developed world.

As stated by its name, AMD is a disease of the macula, that area of the eye that is the most sensitive part of the retina.

Our retina, located on the rear wall of our eyeball, is where the images we perceive are received as different frequencies of light waves, and translated into electrical signals to be sent to our brain, where they are processed into the images we actually see.

The retina is able to do this as it is made up of specialised photoreceptor cells that are sensitive to light.

These photoreceptor cells can be divided into two main types, named after their shapes: cones and rods.

Each type has its own particular speciality; cones enable us to make out fine detail and colours under daylight conditions, while rods provide our sight in low-light or night conditions.

The macula contains most of the cone cells in the retina, hence, enabling us to read, write, drive, recognise faces, and do fine work, like sewing and handicraft, among others.

These cone cells are particularly concentrated in the fovea, which is the central region of the macula.

The macula itself is located next to the optic nerve bundle, which sends the signals from the eye to the brain.

Wear and tear

There are two forms of AMD: dry AMD, which makes up 80% of cases, and wet AMD, which comprise the rest.

Dry AMD is essentially caused by the breakdown of the photoreceptor cells in the macula.

The scary thing about this condition is that it is untreatable, and symptoms only start to show up after it has progressed to the intermediate stage.

In addition, it is primarily a condition of old age, due to the wear-and-tear our eyes go through after functioning for several decades of our lives.

And its incidence is increasing in Malaysia because as Dr Fong points out, “our population is growing older and living longer”.

Although its symptoms, like blurry vision, requiring more light to see and loss of central vision, only show up later in the progression of the disease, dry AMD can be picked up earlier by eye specialists.

Part of a regular eye examination – ideally done once a year – includes dilating the eye to give the ophthalmologist a better view of the interior of the eyeball.

This method enables the doctor to better detect yellowish deposits called drusen on the retina, which are a sign that dry AMD might develop.

Dr Fong explains that as we grow older, a cellular layer called Bruch’s membrane, located between the blood vessel-rich choroid and the waste-processing retinal pigment epithelium (RPE), becomes less permeable.

This causes the waste from the RPE to start to accumulate on the membrane, which results in drusen. (The RPE is in charge of processing waste from the photoreceptor cells, which are located just next to it, on the opposite side to Bruch’s membrane.)

However, Dr Fong notes that while all cases of dry AMD have drusen, not everyone with drusen will develop dry AMD.

Preventive diet

You might be asking at this point why should anyone bother undergoing an eye examination every year to detect this condition when it cannot be treated anyway?

The reason is, research has shown that the progress of AMD can be prevented and slowed down by certain foods and nutritional supplements.

Consultant dietitian Goo Chui Hoong shares that a major clinical study called the Age-Related Eye Disease Study (AREDS) had found that a high-dose combination of vitamin C, vitamin E, beta-carotene, and zinc, delayed the progression of the disease.

The results of the study published in 2001 showed that those at high risk of developing AMD, including those with intermediate AMD and advanced AMD in one eye only, had their risk of the disease progressing further lowered by 25%, and their risk of vision loss lowered by 19%.

However, no apparent benefits were seen in those who had early or no AMD.

“So, diet is the only way to delay it, and there is definitely evidence to support that,” she says.

Goo adds that while there are plenty of nutritional supplements available in the marketplace, consumers who want to delay their AMD must be careful to ensure that they get the right doses as the AREDS concentrations are higher than the norm.

In addition, they should consult their doctors before taking such high dose supplements as such high doses might have adverse effects under certain conditions.

The effective concentration of the antioxidants taken in the study were 500mg of vitamin C; 400 I.U. of vitamin E; 15mg of beta-carotene; 80mg of zinc as zinc oxide; and 2mg of copper as cupric oxide to help prevent copper deficiency due to the high levels of zinc consumed.

Goo also shares that the current ongoing AREDS 2 study is looking at the effects of replacing the beta-carotenes in the original formulation with lutein and zeaxanthin, as well as examining the effects of adding omega-3 polyunsaturated fatty acids to the group of supplements.

“Certain beta-carotenes are used in the AREDS formulation now, but they cannot be taken by smokers because it increases their risk of lung cancer,” she explains.

“In AREDS 2, the beta-carotenes are replaced by lutein and zeaxanthin, which are xanthophyll pigments found in the retina that help protect it against UV rays.”

These pigments need to be obtained through the diet, and are particularly abundant in green, leafy vegetables.

This fact also explains why previous research has suggested that people who eat a lot of such vegetables have a lower risk of developing AMD.

Goo suggests that in addition to eating more green, leafy vegetables, those who wish to prevent or delay AMD can increase their intake of oily fish like salmon, sardines and tuna, which contain omega-3 fatty acids, as well as modify their diet to a low-glycaemic one.

The results of the AREDS 2 study are expected to be out next year.

In addition, certain risk factors for AMD like smoking, an overall unhealthy diet and a sedentary lifestyle, can be changed with some willpower. Other risk factors like growing old or having a family history of AMD, unfortunately, cannot be avoided.

Bleeding in the macula

Because of the high density of photoreceptor cells in this area, the macula is well-supplied with blood vessels that provide them with oxygen and nutrients, and remove waste.

As we age, abnormal blood vessels start to grow into the macula from the choroid, which contains most of the eye’s blood vessels.

These blood vessels tend to be fragile and leak blood and fluids, causing haemorrhage and swelling in the macula, which results in wet AMD.

Symptoms in wet AMD, like seeing straight lines as wavy and developing a blind spot in the centre of your field of vision, develop more rapidly than those of dry AMD.

This is probably a good thing in a way, as wet AMD can be treated, and the sooner it is treated, the better the chances of preserving your vision.

There are two main forms of treatment for this condition: injections of anti-vascular endothelial growth factor (VEGF) and photodynamic therapy.

In wet AMD, there are abnormally high levels of VEGF secreted in the eyes, which promotes the growth of new blood vessels. The anti-VEGF injections aim to block this growth.

However, this treatment needs to be repeated as the abnormal blood vessels will grow back again.

As Dr Fong puts it: “It is like spraying herbicide on lalang, after one month it will grow back again because we can’t kill the roots.”

There are two drugs that can be used for this treatment: ranibizumab and bevacizumab.

According to Dr Fong, the main difference between them is their price and approval for use in wet AMD.

While ranibizumab has undergone specific clinical trials for the treatment of wet AMD and has been shown to be effective, bevacizumab, which is only approved for use in certain tyoes of colorectal, lung, kidney and brain cancers, has not.

However, many doctors have been using bevacizumab off-label (ie without official approval from drug authorities) to treat wet AMD.

And last year, they were proven right to do so when the results of the two-year Comparison of AMD Treatments Trials (CATT) showed that both drugs produced similar results in treating the condition.

Equally important, as Dr Fong shares, is that the cost of one injection of ranibizumab is RM3,100, while bevacizumab costs RM100.

Another treatment for wet AMD is photodynamic treatment, which Dr Fong says can be used for certain types of wet AMD.

In this procedure, a drug called verteporfin is injected into the patient’s arm, which then travels through the body, including into the blood vessels in the macula.

When the drug reaches the macula, the ophthalmologist shines a laser beam into the eye to activate the drug to destroy the new blood vessels, and slow the progression of the condition.

Check your eyes

For Dr Fong, the take-home message is for Malaysians over 60 to regularly check for AMD and other eye conditions.

“Very often, patients don’t present (to doctors) until they have lost sight in both eyes because the condition is not painful,” he says, adding that most people are also unaware of AMD in general.

These observations, in addition to the facts that dry AMD can be delayed by diet and wet AMD can be treated if caught early, are what inspired him and his wife, Goo, to co-author a book called Food For Your Eyes.

Published by Star Publications (M) Bhd, this bilingual book in English and Chinese presents both information on common eye diseases and recipes that help promote eye health.

AMD, and dishes that incorporate nutrients to help prevent and delay it, form an important part of the book.

Food For Your Eyes will be available in major bookstores and selected Klang Valley Focus Point outlets from next month onwards.