I have Rudy project Rydon with transition lenses and an Rx insert. The Rx insert if frameless so I barely notice it. Haven't experienced any issue to date with fogging, etc. between the two lenses. I'm going to buy grey lenses so I can use the glasses for driving (the transition doesn't work in the car - no UV). With my prescription I could have gone for Rx lenses, but these are my first real glasses, progressive lenses at that, and I want to make sure my Rx is stable before springing for the addition $s.