Prescription Goggles

I have a great answer to a different question. And maybe have an answer to your Q.

SWIM goggles are available on eBay for as little as $7.50 in mild, moderate and strong corrections and those have served me well in the swimming and for the quick snorkeling swim in the tropics. I also like that I have a back-up pair of (admittedly goofy looking) glasses should my primarily pair go missing. And for something like running Lava Rapids in the Grand Canyon – they are superior to regular glasses. All the ones I've gotten have plastic lens that do scratch over time. But I get 3-4 years of pretty regular use out of them.

SWIM masks are also available for a LOT less than your optometrist wants to charge. $59-$69 with your choice of diopters in each lens (I got my MIL her far-sided / near-sided corrections address in a single mask at the same price). Those have glass lens and hold up fine to sand in the swim bag.

But back to your Q: How about something like this?

http://www.zennioptical.com/706416-prescription-wind-goggles.html

$27.95 with single-vision lens included, I believe.

I would expect those would work a lot better than prescription glasses inside of OTG goggles which, I agree, never work very well. A little soap film on the inside of any glasses or goggles helps prevent fogging up.

This has an insert that can go in most goggles. I ordered this (hasn't arrived yet) to use the Rx insert in a different goggle.

http://www.zennioptical.com/703318-prescription-wind-goggles.html

I believe that is using this insert:

http://www.liquidationsports.com/index/page/product/product_id/16877t/category/85/category_chain/49,85/product_name/S4+Optical+Armour+Rx+Goggle+Insert

If you order that insert it does not come with Rx lenses. Ordering the lenses from the manufacture is about $100, so the Zenni Optical one seems like a good deal. The cheapest I have found those inserts with Rx lenses is $70, other than the Zenni Optical one.

Another good company to deal with:

http://opticus.com/