What a concept! I had never heard of piano glasses. I knew about reading glasses (been using them a bit longer than I care to admit) and computer reading glasses, but piano glasses....interesting. The idea of having glasses especially made for the piano has stayed with me and I started to do some research into the idea. I found that the traditional distance for reading glasses is about 14-16 inches and the distance for computer glasses is about 18-20 inches. So, I sat down at my piano (using proper posture) with a tape measure and found my piano music reading distance to be 22-24 inches. That is significant focal length difference and will definitely impact an eye prescription. (Here's a pretty interesting article for optometrists on eyeglasses for musicians.) I imagine this difference can vary depending on the individual, so it is probably important to measure yourself at your own piano.
So, I have been noticing lately that my own eyes have been changing a bit with respect to my reading (and piano) focal length. It has been harder to practice my own music because the musical notes have become a bit more blurry. So, I'm going to have to schedule an appointment with my optometrist for a new glasses prescription and this poses a bit of a dilemma. Glasses are expensive, should I get a pair of reading glasses and a pair of piano glasses? Upon reflection, I think I'm probably going to get a new pair of blended bifocals and a separate pair of piano glasses, which means I'm buying an extra pair of glasses. However, I love my piano, I think it will be worth it.