I have three pairs of glasses of different widths and have tested them with the Vive. They measure 130mm, 140mm and 150mm respectively in width.

The Vive is designed for glasses both in relation to the distance of the lens from one's face, and the design of the foam padding. The foam has cutouts on the left and right side which appear designed to accommodate the arms of glasses.

My 130mm glasses are the most comfortable. They appear to be narrower than the maximum usable width in the Vive. As a result, there is no noticeable pressure on the glasses' arms. In fact, wearing them with the Vive isn't any different than wearing them otherwise. The only ergonomic issue occurs when putting on or removing the Vive. I just have to be a little more careful doing so.

The 140mm glasses are at the borderline of comfort/discomfort. Their arms touch the interior sides of the foam. As a result, there is some pressure when wearing them in the Vive. It might be possible to alleviate this by removing a bit more of the foam. Loosening the headset also helps, but then results in a less secure overall fit.

The 150mm glasses are very uncomfortable. Because they are wider than the foam can reasonably accommodate, wearing them results on a distinct pressure on the face (both sides and the nose). Even moving the headset away from the face does not relieve this pressure.

Glasses up to ~135mm or so should be perfectly usable with the Vive. Anything larger and one would need to adjust the foam padding or the headset for comfort. Anything over 140mm is going to be tough to wear comfortably. At that point, contacts would be the better choice.