Eye The human eye. The retina of the eye contains about 137 million light sensitive cells in an area of about 650 sq. Mm/ 1 sq in. There are 130 million rod cells for black and white vision and 7 million cone cells for colour vision. The optic nerve contains about 1 million nerve fibres. The focusing muscles of the eye at just about 100,000 times a day. To exercise the leg muscles to the same extent would need a 80 km / 50 mi walk.
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