I have seen some posts that I can not find now, not even sure it was on this forum as I read a couple. But, have seen references to the Merit and the Lyman optical focus thing that attaches to your glasses with suction cups, have heard that some like them some do not. I found my clip on optical aid and looked them up on the web, they are still in business. They cost as much as the Merit, but are easier to adjust. Here is a link to Walters spectacle clamp:
http://www.lssproducts.com/product/4544/walters
http://www.lssproducts.com/product/4544/walters