Zinc could be key to eye disease

The mineral zinc may play a role in the development of a common cause of blindness, research suggests. Age-related macular degeneration (AMD) is the leading cause of blindness among elderly people in the developed world. Researchers found high zinc levels in deposits in the eye which are a marker for AMD development. The study, published in Experimental Eye Research and led by London's Institute of Ophthalmology, could help the development of new treatments.

AGE-RELATED MACULAR DEGENERATION

More common in women

There are two forms: dry and wet

In dry AMD, visual cells stop functioning and die

Wet AMD, a more aggressive form, is linked to new vessel growth

There is no treatment for dry AMD

Wet AMD can be treated with photo-dynamic therapy, and drugs that stop new vessel growth

However, treatments are only suitable for the early stages of disease

AMD is a form of macular disease which affects the eye's retina, and causes loss of central vision. An estimated 500,000 people in the UK have it, including 40% of people aged over 75. An early sign of the disease is the formation of microscopic structures called drusen in the eye. Exactly what the effects of these are and why they form is not yet fully understood. The latest research found that drusen in eyes with AMD contain very high levels of zinc.

Researcher Dr Imre Lengyel said: "Zinc had previously been shown to contribute to the formation of plaques in the brains of patients with Alzheimer's disease, so it was logical for us to test the idea that zinc might also contribute to the formation of plaque-like drusen in the eye as well. AMD can be considered as the Alzheimer's disease of the eye, in that both involve the build-up of proteins and metals like zinc and copper into microscopic clumps."

The researchers found that a small pool of the zinc - 5-10% - was of a type known as loosely-bound or free zinc. Generally, zinc is essential to keeping a molecule's shape, but free zinc can cause lots of problems. They believe, because it is a small proportion of the overall zinc pool, it should be straightforward to target it. Alzheimer's researchers are already developing drugs that can capture free zinc, and hope that their use will be able to slow down the degenerative process.

Dr Lengyel said: "This study shows that we could now potentially take a similar route for AMD treatment."

The Macular Disease Society agreed the research had the potential to contribute to the development of new treatments - but said more work was needed. However, a spokesman said previous research had found that zinc plays a positive role in delaying or reducing the onset of AMD. He said it was important that patients sought medical advice before changing their diet, or use of nutritional supplements.