How exactly does it affect night vision?

I already have mild cataracts which make night vision annoying. Definitely don’t need it getting any worse!

Starburst and halo artifacts are the keywords to get an idea.

The specifics are hard to estimate, since severity is fairly subjective, but it's pretty common for things like traffic lights at night to show them.

They can replace your eye's clouded lens with a corrective lens now.

They can even do bifocal lenses when replacing them. My mother just had this done and I was surprised to see that as an offering.

So as a getting-older-over-halfway-done guy, my night vision is already pretty crap. Are you saying it will get even worse?

They reshape an area smaller than a fully dilated pupil, so night vision is affected because you're seeing light that passed through the corrected area and light that passed through the uncorrected area (and the boundary itself might mess things up in a more complicated way). Whether that sort of distortion is "worse" than entirely uncorrected vision is kind of subjective. Also, I think that effect diminishes with age because the pupil doesn't dilate as fully.