Are there any negative effects of using contact lenses?

Question

For example, do they scratch your eyes?

Answer 1

The eye's cornea receives oxygen from the atmosphere and contact lenses must be permeable to let in the oxygen or worn for specified limited periods if not permeable.  Contact lenses can change the perceived size and location of objects (look through your glasses held a foot away and move them nearer and farther away, contacts are as close as can be).  Contact lenses can be dangerous if you work with chemicals as they will hold the chemicals close to the eye in an accident.  If not properly maintained and cleaned with special fluids eyes may be prone to serious infections.

Answer 2

my friends brother was playing basketball one day and his contact sliced his eye because he got hit. but i played basketball with them and i havent had any trouble with them. i have had them for over 2 years now and not one problem. they are waayyyyy better than glasses.