When light enters the eye it triggers a 'beautiful' cascade of chemical reactions, some of which our brain processes and recognises in the form of vision, he says. "But this cascade of events also causes collateral damage to the eye so, in simple terms, light both causes us to see and also harms the organ we see with by causing oxidative damage to the vision cells.

"We do extraordinary things with light – but we also pay a high price for it."

This loss of photoreceptors leads to gradual dimming of vision in advancing age, which is first noticeable from the eye's failure to detect very faint light in dark conditions. Ultimately it can lead to complete loss of vision.

The main way to avoid this is to limit the amount of light entering the eye throughout life, but especially during middle and old age. "Most sunglasses will reduce by 25-50 per cent the amount of outdoors light from entering the eye and, knowing what I now do as a result of years of work in this field, I never go outside without my sunnies," Professor Stone says.

"Other groups at the Vision Centre have found a certain amount of light is necessary to prevent eyeball distortion and myopia in childhood and adolescence – and this is a beneficial effect.

"But we should be aware that harmful effects also result from over-exposure to light, so it is a case of striking the correct balance between more outdoor exposure in youth, to prevent myopia, and greater use of light protection in the form of sunglasses to prevent age-related degeneration.

"After the eyeball has stabilised, from one's 20s on, it is a good idea to wear protection at all times when in bright conditions.

"This will result in a larger population of photoreceptors in advanced age, and will be especially important for those whose genes predispose them towards the loss of these vital cells."

However, the good news is that damage to the photoreceptors may be treatable. Recent experiments point to a diet high in protective antioxidants as one way to slow the loss of vision into age, and new research is uncovering other methods by which damaged sight may even be improved.

"It appears that by managing the oxygen levels in the eye, through diet and other methods, we can slow down and possible even reverse the loss of photoreceptors, and we are planning a clinical trial to test this idea," Professor Stone says.

"If it confirms what we think is going on in the eye, then it may be possible both to preserve sight into old age much better – and maybe even to improve it by some quite simple treatments."

Source-Medindia
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