I just bought a pair of glasses on the internet. It was a good experience.
My situation was the simplest possible. I sent them a pair of old scratched-up glasses and said, “Replace the lenses with identical new lenses but make them photo-active.”
There was a little more to it than that, but not much. They cost less than half as much as they would have at a “normal” optician, and even cost less than they would at Costco.
I opted for the Transitions XTRActive lenses, which darken with exposure to light. They are a new version that gets darker with less light than before– they darken a little even while driving in the car, and darken quite a bit even when I wear a hat that shades them. Regular Transition lenses are a lot less active in those circumstances. The downside is that they take longer to clear up and never become completely clear, but close enough. I tried Transitions before and was disappointed on the limited darkness in many situations. So far I am very happy with these.
After some research, I used ReplaceALens. There are a lot of other reputable companies, but they had the best set of options and had very good BBB and user reviews. I sent them a question by email before I bought and they were very responsive. And while making my glasses they called me with a question to clarify something. All in all I liked working with them and the glasses they sent me were perfect.