The glasses industry is criminal. There is absolutely no reason that glasses should cost hundreds of dollars. There is absolutely no reason that an eye exam should cost hundreds of dollars. There is absolutely no reason that you shouldn't have the power to adjust vision correction yourself on the fly. Single prescription lenses are not ideal for all situations.
The current incarnation of this product is a first step in solving these problems. It isn't perfect. But for about 29.95 dollars, it's incredible, especially for a person who needs comfortable medium range focus, like on a computer display. With normal prescription there can be a lot of fatigue trying to focus on medium range for long periods of time. With this, you can easily dial in a level of correction that works perfectly for computer use.
You don't need to worry endlessly about damaging or losing overpriced glasses.