Hypoxia occurs when the
cornea does not get enough oxygen. It is the most
common complication of contact lens wear, especially extended-wear
The cornea has no blood supply of its own, so it gets oxygen only
from tears and directly from the atmosphere. A contact lens reduces the oxygen
supply to the cornea, making the cornea swell. Wearing contacts overnight
further decreases the amount of oxygen that gets to the cornea.
Gas-permeable hard contact lenses have almost eliminated some
problems, such as overwearing syndrome and corneal clouding. Problems that still occur include hazy vision caused by mild corneal swelling
(edema) or warping. Over time, corneal hypoxia may cause serious problems with
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