Prescription Sunglasses

Don't believe bullshit about tints increasing night-time vision. Clear is the way to go.

I gave up on cycling-specific stuff, and now use an old pair of specs. As long as they fit well, aren't too heavy, and have reasonable vertical coverage, they're great. And some of the larger lensed options can be had for £25 to £75 at places like Specsavers (their bog standard single vision lenses are as scratch resistant as more expensive plastics with coatings).

Yellow Lenses and similar coatings do actually increase contrast very effectively in low-light/night time conditions, which make objects even easier to pick out in the dark.
Giving you a more detailed view of the scene, they don't do much to make things appear brighter though, but increased contrast is really helpful.