Zinc Provokes Blindness

The mineral zinc seems to play an important role in the development of a common type of blindness.

Age-related macular degeneration (AMD) is the main cause of blindness among elderly people in the developed countries and scientists have discovered that high zinc levels in the eye's deposits signal AMD development.

AMD damages the eye's retina, and provokes loss of central vision. About 500,000 people in the UK (8 %) suffer form this, including 40% of people aged over 75. An early symptom of the disease is the emergence of microscopic structures called drusen in the eye, whose effects and why they form is not yet precisely known.

The latest investigation discovered that drusen associated with AMD present very high zinc levels. "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", said Dr Imre Lengyel.

5-10% of the zinc belonged to a type known as loosely-bound or free zinc. Normally, zinc is crucial to maintain a molecule's shape, but free zinc results to be much trickier. Scientists consider that as the free zinc is a small proportion of the overall zinc quantity, it would be easy to target.

There are already drugs developed against Alzheimer's that capture free zinc and slow down the degenerative process. "This study shows that we could now potentially take a similar route for AMD treatment", Lengyel said.

The Macular Disease Society believes the research could contribute to the development of new drugs, but more investigation would be necessary. However, "previous research had found that zinc plays a positive role in delaying or reducing the onset of AMD", said a spokesman of MDS. "It is important that patients seek medical advice before changing their diet, or use of nutritional supplements."