I'm pretty short sighted. If I tell you I once sunk my teeth into a matchbox at a party thinking it was a sandwich you will have some idea how bad it is.

I use Oceanic masks because my LDS have prescription lenses for them under the counter. They don't do exactly every prescription - if you are -4.25 you have to settle for -4.00 ( bit weaker ) or - 4.50 ( bit too strong ) but overall they give you good vision underwater.

Cost is about £25 per lens and you simply remove the plain glass and fit the new lenses in its place taking care to make sure you do not compress the thin plastic seal/flange which is around the lenses or they will leak like sieves. I do the replacement myself in 5 minutes total.

Makes it a bit more expensive if you lose your mask though.