I'm -9.5 in my left eye and -8.5 with added astigmatism fun in my right. So the lenses are fairly complex I suppose, and then they have to be the extra thin and light ones so that my glasses aren't forever falling down my nose. The only optional bit really is that I get the anti-reflection coating but that's only £10 per lens normally!

I have a diving mask made with standard glass; the left lens is well over an inch thick at the edges and it sinks like a stone so I have to tie it on to me whenever I use it!