Keratitis (pain, dryness, photophobia, redness of the eye, injections in the eye area, a small speck at the site of inflammation). And then - hello glasses and goodbye lenses for a few months at least.
As someone who once wore one-day lenses for a week due to the fact that all the shops were closed for the holidays, I can say: nothing. Every day I listened to the sensations, fearing that today the eye would certainly start to hurt terribly or stop seeing at all, but nothing happened. Although, of course, it's better to wear it according to the rules, since research says that.
The lens material for daily wear is designed for daily lens changes. With prolonged wearing of such a lens, its physical properties are lost, which leads not only to a deterioration in visibility through such a lens, but also to reddening of the eye (due to a decrease in oxygen permeability) and to infectious complications. It is known that the risk of developing bacterial corneal damage (keratitis) is higher in those people who prefer to wear extended-wear lenses. Studies have shown that when wearing a daily lens, the risk of keratitis is 5 cases per 10 thousand people, and when wearing extended wear lenses - 12 cases.