Eye facts

Did you know...

• that an eye is only 2.3 centimeter long on average?
• that the eye lens sits within an envelope that is the thickness of a red blood cell? This envelope is what contains the artificial lens after a cataract operation.
• that tears are meant to protect your eye? They contain natural antibiotics, they prevent the eye from drying out, they contain certain fats that reduce the evaporation of tears.
• that the eye makes an aqueous fluid in side it, so the eye has a certain "pressure"?
• that the retina contains 120 million rods for "night vision", and 8 million cones that are colour sensitive and work best under daylight conditions?
• that light causes electric activity in the eye, that can be measured, and is sometimes used in tests to find out how the retina and the nerve of sight works?
• that modern cataract operations have been made possible thanks to the second world war? Sir Harold Ridley, who was an ophthalmic surgeon in London, found that pilots came back from their missions with little pieces of perspex in their eye(shattered screens of the planes they were flying in), to which the eye did not seem to "object": no inflammation of any significance was found in their eye.This material was modified and further developed into artificial lenses that are used in cataract operations.
• that about half of our brain is involved in the seeing process? Humans are very much visual animals.