Sydney, Jan 8 (IANS) Excessive exposure to light causes deterioration and loss of vision gradually over life, new research says.
'There are about 150 million light-sensitive cells - known as photoreceptors - in each eye. All through our life we lose these at a steady rate of hundreds every day, but some people lose them much faster than others, with the result that they go blind, sometimes quite early in life,' said Jonathan Stone of the Vision Centre who led the research.
These photoreceptors are remarkably tough, and most people still have 100 million or so left by the time they reach their 70s or 80s, Stone said.
However in later decades of life these eye cells begin to lose and eyesight gets dim.
The eye contains many highly-specialised genes, which produces many random mutations. These mutations are responsible for more acute degeneration of retina than normal fading in some people, the research says.
'However there are also some environmental factors which cause the eye to lose photoreceptors more rapidly, especially in people with a certain genetic make-up,' said Stone.
When light enters the eye it triggers a 'beautiful' cascade of chemical reactions, which brains recognise in the form of vision.
The loss of photoreceptors dims the vision and the eye fails to detect very faint light in dark conditions. Ultimately it can lead to complete loss of vision.
'We do extraordinary things with light - but we also pay a high price for it,' Stone maintained.
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