The front window of the eye is called the cornea. It contains no blood vessels so that we can see through it clearly. Contact lenses can actually inhibit the amount of oxygen that reaches the cornea. Overwearing contact lenses can create a hypoxic condition in which the body creates new blood vessels to carry oxygen through the blood stream. This is called neovascularisation and I see it a lot in patients that are wearing older generations of contact lenses.
Fortunately, for a few years now, we have been able to prescribe contact lenses with much higher oxygen transmission. Make sure you’re wearing contact lenses that the eyes breathe.