I gave semi high dose lutein (45mg per day) a try as I noticed my eyes weakening (early problems with long-distance vision, night vision). Helped substantially, took maybe two months to have a noticeable effect though.
Sometimes people's vision prescriptions are too strong. I started going to a 'developmental optometrist' about 12 years ago. While I don't see 20/20 with my current glasses, I tried stronger lenses from a conventional optometrist 7 years ago and found them intolerable. When he wanted to charge me for another office visit for the contact prescription, I just ordered the prescription I wanted from an internet contacts store.
I guess if you just start using them you'd want an expert advising you, making sure everything goes correctly?
Many sites let you just punch in the numbers. The downside is that you need to make frame adjustments yourself or go somewhere to do it.