On reading glasses

I got quite a shock when I went to get new glasses a little over a year ago. I went to an eye doctor and got a prescription and took them to Wal-Mart, and they made me a pair of glasses. So far, so good. And when I used them to look far away, I could sell well. But when I sat in front of a computer screen, my eyes rebelled. The eye doctor at Wal-Mart told me I'd need a separate prescription for working at mid-distance, such as sitting in front of the computer. I was shocked. When I was a kid I was told I'd need reading glasses when I hit age 40. Well, that was nearly 20 years ago and I still read without glasses. But now I need a different pair to see a computer screen than the pair I used to look into the distance such as to drive or watch movies with.