A quick update on this.
I received my Adivista frames with prescription lenses a few weeks ago. Here's what they look like:
My prescription is pretty high (-4.75 in each eye), so I was right on the limit of what could be achieved with these frames and the lens technology. But the outcome was excellent.
The lenses are 1.67 index (super thin) and aspheric. This means that they are highly curved around the eye and have a variable strength depending on how far from the optical centre you are. This means that the lenses are very thick at the outside edge (you can see this in the 2nd pic) but are still quite thin in the middle.
The overall effect is initially unusual. It's like a mild fishbowl vision because your periphery is far more covered by the lens than you'd have in normal glasses. I wore them around the house for a few hours and it was a bit mad - bumping into things, ended up with a slight headache.
But these glasses are not for everyday use. At the table they work very well. It does take a few hours to get your head around what they're doing, but you adjust very quickly and any initial strangeness is now gone. It's a bit like changing between glasses and contacts all the time - initially things seem different and strange when you switch, but after a few days of switching your brain seems to get used to the adjustments needed. Same with these glasses - I keep them in my TT bag and put them on when I get to the venue and I'm ready to go now.
The frames are excellent - clicky adjustment in the arms and nose supports mean you can get a nice close fit. The arms have a soft plastic section at the end which gets a bit grippy when you sweat, so they can't ever move around during play. Having some clear vision in your peripheral vision is a big bonus for TT, so the lenses are a great help (once you're used to what they do!). The lenses aren't perfect all the way around and the correction is worse towards the outside edge, but still far better than nothing at all. This is probably more to do with my high prescription though.
In short, not quite as good as contacts, but far better than regular everyday prescription glasses. Anyone who has issues with contacts (as I do now) might find some benefit from this kind of solution, but it's a fairly expensive gamble I suppose.
Many thanks to
www.eyekit.co.uk for all their efforts in sorting this out for me.