Recently, I installed "Adobe Photoshop Version: 19.1.0 20180116.r.238 2018/01/16: 1153018 x64" and...
Now, "UI Scaling" to 200% doesn't work.
In previous version both options, "UI SCALING" and ""UI Fonts Size", were working very well
EDIT -> PREFERENCES -> INTERFACE.
Do you know if the bug is reported and team is working to fix?
For people with problems in Eyes is very disturbing this issue.
If you have Win 10 Creators Update, and the PS 19.1 update - scaling is now set in the Windows Display scaling. Photoshop will pick that up and the PS prefs don't do anything.
See the countless other threads about this. It's getting hard to keep up with them all.