AMD can increase risk of stroke

Dec 4, 2010

The Business Times

By Cheah Ui-Hoon

SO you think eye problems are confined to the eyes? It turns out that having age-related macular degeneration (AMD) can increase your risk of stroke. AMD is a chronic degenerative disease of the macula – the central part of the retina.

In the Atherosclerosis Risk In Communities (ARIC) Study, people with early AMD signs had double the risk of incident stroke over 10 years. This was based on a population study done in the US. The results were published in the Journal of Stroke a few years ago, but it’s a fact that’s rarely known, says Peter Kaiser, a retinal specialist and principal investigator of over 30 clinical trials on AMD and other retinal disorders. 

“This is a new finding. It’s not something we thought about in the past,” says Prof Kaiser who was in Singapore for the 5th Congress of the Asia-Pacific Vitreo-Retina Society last month.

It’s a situation that makes sense however, as a lot of the risk factors for AMD are similar to cardiovascular disease, says the professor. “Factors like increased cholesterol levels and high LDL, a large waist circumference and high body mass index are factors for both AMD and stroke.”

If one just looks at the AMD population, there isn’t an increased risk of stroke in that population; only in the population-based study. But it correlates with other studies that suggest there is an increased risk of stroke in AMD patients. “And the risk is two-fold, as suggested by another study of Medicare patients in the US,” says Prof Kaiser.

Risk factors
Previously, AMD was seldom highlighted as a condition because there were few solutions for it. But the situation is different now, as there is an effective gold standard treatment for wet AMD. There are dry and wet forms of AMD, with the wet form being more dangerous because it means blood vessels are growing in the eye, which then bleed and leave scars if left untreated. This can lead to a severe loss of vision and cause blindness. 

“It’s the leading cause of blindness in the West,” the professor adds. In dry AMD, there are underlying inflammatory conditions, but it doesn’t cause loss of vision. AMD affects those above 50 years old, and while one may have a genetic propensity for it, smoking increases risk. Caucasian females are also more prone to getting AMD. But all the other risk factors for cardiovascular disease apply, such as being overweight, having high cholesterol and low intake of Omega 3 fatty acids.

Blindness can be avoided, however, if risk factors are modified through diet and exercise. “It’s not a death sentence . . . as you can work on improving the odds. The majority of wet AMD patients need not go blind,” says Prof Kaiser. One in four people in Singapore above 60 years old has AMD.

The causes of AMD are not known, except for general conditions such as a poor diet and low levels of anti-oxidants. “The eye is one of the most active structures in the body as it’s constantly converting light into neural waves. And that takes a lot of energy,” the professor explains.

“If one smokes or is low on anti-oxidants, that lowers the ability to deal with the excess energy, so this causes damage to the eye itself. Because of genetics, there’s baseline inflammatory damage in the eye . . . that is exacerbated by light damage.”

In the beginning, symptoms may not be very noticeable. Only in advanced AMD does one notice distortion and reading becomes more difficult, starting from the centre of vision. By changing lifestyle, and taking dietary supplements such as anti-oxidants, one can reduce the risk of progression from the dry to the wet form of AMD. The condition can’t be reversed however, and there’s no operation that can be done at this time.

AMD is directly related to nutrition, diet and other modifiable risk factors. The treatments for it include laser and photodynamic therapy, and the new anti-VEGF therapy from Lucentis. Lucentis’s new anti-VEGF therapy can now stabilise and even improve vision in about 90 per cent of AMD patients. Some 30 to 40 per cent of patients see significant improvement, so it’s a huge step forward compared with other treatments.

Anti-VEGF (anti-vascular endothelial growth factor) treatment helps reduce vessel formation, bleeding and swelling in the eyes. Lucentis was specifically designed for injection in the eye and is generally safe and well tolerated. Eye specialists usually do three monthly injections first and post frequent monitoring to see if subsequent injections are needed.

It doesn’t hurt, Prof Kaiser assures. “Flu shots hurt more than this,” he adds. The solution blocks the growth factor responsible for the growth of the new blood vessels. The treatment has been available in the US for a while now, and in Singapore since 2008.

Lucentis’s anti-VEGF treatment is now the gold standard for wet AMD. “It prevents loss of vision, but it doesn’t reduce risk of stroke, which can’t be prevented unless the risk factors are improved upon,” says Prof Kaiser.

For the dry version of AMD, there is no proven treatment for it now, but what slows it down is supplemental vitamins, especially anti-oxidants, which can reduce the risk of progression by 30 per cent.