Hi there - can only tell you what happened to a friend of mine - she kept her monthlys in for 2 - 3 months and when she went to opticians, he said she had some uneveness under eyelid which can in time scratch the eye. Apparantly, if they turn your eyelid inside out (which my optician does to me too on my annual checkup) they can see the state of the inside of your eyelid and the skin surface needs to be smooth and clear. My friends were lumpy and these lumps can irritate your eye - the optician did say that she needed to have changed her lenses more often to avoid these 'old' lenses from damaging the skin under her eyelids, and in turn scratching her eye. Hope this helps.