Buying glasses online

I recently went looking for a light-weight rimless replacement for my old Silhouette glasses that had become scratched and chipped.

I went to http://www.zennioptical.com/
And chose frame 377411 with high index 1.67 lenses (+ AR coating)

So far, I've been extremely satisfied with them. They weigh 9 grams, which is only 1 gram more than my old glasses. I'm also happy because the base curve for each lens was correct (something I've had problems with at a traditional optician). I own a lens clock and a lensometer, which gives you an idea of how often I've had issues.

The clip-on shade doesn't really work that well, but at 1/5th the cost of Silhouette I can afford to buy a pair of prescription sunglasses (also from Zenni). The nose pads are easy to adjust for a perfect fit.

The High Index 1.67 lenses are visibly thinner than my polycarbonate lenses, but I haven't measured with a caliper for fear of scratching them. For small lenses it probably makes more sense to save your money and get high index 1.61 instead.

So far I've ordered three pairs of glasses from Zenni and the prescription was within 1/8th of a diopter each time. This is enough of a variance to give some people a mild headache when switching between glasses. 3 out of 6 lenses were 100% accurate.

In the future I'd like to try ordering from europe (although it's much more expensive):
http://www.brille24.de/