The cornea is unusual in that it is transparent – it has to be otherwise light could not enter the eye! The tissues that make up the cornea are able to maintain their transparency partly by not having blood vessels flowing through them. Without blood vessels the cornea must get it’s Oxygen directly from the air. The Oxygen first dissolves in the tears and then diffuses throughout the cornea to keep it healthy. Equally important, the waste product of a healthy cornea is Carbon Dioxide which must be disposed of. This diffuses out of the cornea and into the atmosphere in the reverse process. Putting any contact lens into the eye will slow down or possibly stop this process. Without enough Oxygen the cornea will warp, become less transparent, less able to detect pain and can develop scars. Additionally, new blood vessels from the sclera (the white part of the eye) can grow into the cornea and cause further damage and scarring.

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