If you're over 40 and have been wearing glasses for years, you might now need a pair with a weaker prescription just for computer use.
What's the reasoning behind being over 40? I recently complained to my optometrist that I was having a harder time seeing things up close and he prescribed me weaker lenses for work/reading. My regular prescription is right around -7 in both eyes. I'm not over 40.
Would love to chat about your experience in any case. I'm at jbornhorst [at] gmail.com if interested.