I had a Pair from Walmart and insisted to lower the Bifocal area.. well they did, So low they were useless..
I have been using Inexpensive Safety Bifocals at work,http://www.safetyglassesusa.com/safreadglas.html?gclid=CLHFx5-6g6QCFZQz5wodNzj-JQ
Many pairs to choose from, cheap prices.

I'm giving wal mart one more try with my new perscription