Darned if I know - this is what I heard from the Hydrooptix people. I couldn't imagine degrading my normal vision for underwater correction to begin with.
Now just for one hypothetical instance, let's say a 20/20 guy did splurge for the mask, went through the contact lens ordeal, and was diving in a cave. If he did have a mask problem, he could ditch the mask for a backup and just pop the lenses out.
One thing in the mask's favor - I got three of them from the factory - is that it is awesomely made. The curved mask lens is polycarbonate, and if you managed to hit something scootering or moving in a fast current that could crack that lens, you'd be speared by a normal glass mask.
Plus the lens is screwed on - you can change it out with an Allen wrench.
I almost eyeballed myself one night on a deep wreck when something hit my leg. Swinging around, I just missed a thin metal pipe sticking out of a bulkhead. I might have scratched the Hydrooptix lens, but I would have shattered my Sea Vision for sure.
So out of my three masks, I gave one away to a tech outfit in Provo to play with, I sold one on eBay, and now I'm down to one. I didn't like it in the ocean, especially looking for the boat after surfacing, but it might actually be kinda cool in freshwater caves.