Well, I am still lacking on the 'scientific knowledge' on the whole process, but basically Dr. Katrina said to 'correct' my vision problem I will be trading one pair of glasses for another. I am nearsighted now but afterwards I will be farsighted (it comes with old age too). I have no problem with needing glasses while sitting, reading, etc. I do have a problem with needing glass while I want to be active outdoors.