Contact lenses are wonderful. I’ve been severely nearsighted since childhood, and I still remember feeling amazed the first time I put in contact lenses. Suddenly, there were no borders on my accurate, focused vision!
But contact lenses come with a host of warnings: don’t get dirt in the eyes, don’t rub at them, and don’t sleep with them still in.
What’s the danger? Why is it okay for us to keep these thin pieces of plastic or glass on our eyes during the day, but it’s suddenly bad once our eyelids are closed?
It all comes down to oxygen — and I’m not talking about the oxygen that’s in your lungs.
Your eyes don’t breathe, sort of
All of the trillions of cells that make up our body need oxygen. It’s a vital part of the reaction that these cells use to “burn” fuel, turning sugar + oxygen into energy. Most of our cells get their oxygen supply from the bloodstream; our red blood cells carry oxygen around for all the other tissues.