My glFrustrum got bigger?

Since I got my new glasses, DVD cases on shelves look suspiciously small. At first I wondered if it was some new smaller design of DVD case. However, DVDs themselves are obviously still the same size, and inspecting a case reveals that it’s only just wide enough to encompass the diameter of the disc. OK, you may think, no mystery here. New glasses. However, my new glasses are exactly the same prescription as the old ones.