Those asking about Lasik:
I'm not an ophthalmologist, I'm not going to be an ophthalmologist, and I've done zero research in this field, but from my (very short) rotation in ophthalmology, my understanding is as follows: Lasik basically corrects your eyesight by shearing the lens in your eye so that it focuses images in the correct place in the back of your eye. However, because shearing the lens means there's less overall substance, the natural breakdown of the lens later in life that causes eyesight problems becomes more irreversible and less correctable.