No expert, but I'd doubt you'd have any claim unless agreed at the time of purchase. On the other hand, they do take a while to get used to, because you've to learn to instinctively look through the right part of the lens without thinking consciously about it. Even now, after years of use, there are occasions when I end up tilting the glasses to ease viewing something. But the option is way better than struggling with one pair of fixed length, or trying to keep tabs on multiple pairs.