This sort of a narcotic does not affect the cornea but the fact that you are dependent on anything suggests your mental weakness and lack of will power. This sort of mental attitude caused you to rub your eyes a lot even in your teen ages, which contributed to your keratoconus in the first place in addition to weakness of the cornea, which may or may not be hereditary. Never rub your eyes if you can help it and strengthen your mind and will power to give up any addiction.