Yazzy, why go for lenses in a mask? Have you considered or tried contacts? How bad is your eyesight? If you dont need good eye correction when on the surface you wont need it underwater.
I am -7 and -6 and found that, I needed to see all the time, not just when I had a mask on, getting in a RIB final part of kitting up. etc. Handing kit to people at the end of the dive etc.
So that I can see all the time, I have gone for soft contacts, I buy them in 60s and use and discard as needed. I do not buy them monthly. Which saves money.
Are you not concerned at losing or damaging your mask and screwing the diving day? I was worried about being on a live aboard and finding half the week wasted. Or will you plan to buy two sets of lenses?
When I went to be checked for lenses I expalined the reason I wanted them and mostly that I wanted to be able to clearly read my DC on my wrist, this actually changed the prescription a bit. It all works, and so far no eye infections, perhaps because at the end of the dive I whip them out and slap on my glasses, of which yes I do carry two pairs.
Worth thinking about.
Wibble