Lens Type Matters
Contact lens type plays a big factor when determining how long lenses can be worn for, according to Vision 2020. Many eye doctors recommend wearing soft contacts up to 12 hours per day, semi-soft lenses up to 10 hours per day, and hard lenses up to eight hours per day.
Eyes Need Oxygen
Wearing contact lenses interrupts the flow of oxygen to the eye, and while contacts are made of a material that allows maximum oxygen absorption, it's not identical to the amount of oxygen received without lenses. If eyes get red, dry or irritated, lenses should be taken out even if the maximum wear time is not reached.
Eye doctors generally agree on the length of time contact lenses can be worn, however it's important to pay attention to any sudden dryness or redness and remove lenses immediately if these symptoms occur.