Custom made masks are available in two versions: (i) inserts for close distance at the bottom (cheaper) and (ii) multifocal (better but more expensive).
Wolfgang[/QUOTE:
There is a 3rd type of custom made mask which I use and work fine for me but maybe not for others: full corrective glass in the mask (not multifocal).
It works fine for me because I have +2 farsight and abour +1 near sight. So, with a full +2 mask I can see fine within the visibilty range underwater (even in clear waters). You can not see objects 50 m farther anyway (underwater). For me is easier than usin bi-focals or multifocals and such masks can be bought for about 50 bucks in amazon
Regards