Took my Goggles to the Optometrist today. He updated my prescription then recommended I go with +4.00 over my distant vision correction (which is +3) for a total of +7.00. Based on some posts from this forum, I told him the focal length was probably close to 11 inches. The resulting glasses work great for me. I checked out the "heart of the envelope" focal length for my prescription and it turned out to be about 10.5 inches. Can't wait to go fly with them!