Thursday, February 4, 2010


Light enters the eye through the transparent cornea  at the front and is then focused by the lens on the retina, the light-sensitive surface on the inside of the eyeboll. The size of the pupil,the hole in the centre of the coloured iris,changes automatically to control the amount of light passing through it. In the retina,light triggers nerve cells which pass nerve impulses along the optic nerve  to the brain,where they give rise to the sensation of sight.

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