Related: Most people over age 30 should see an ophthalmologist at least once every 10 years. An optometrist is generally fine for fitting glasses, but an ophthalmologist will provide a much more thorough eye exam (as well as updated RXes).

(Exception: If someone's vision is 20/20 uncorrected and they don't have any other eye concerns, this probably isn't needed… until they hit the all-but-inevitable presbyopia, likely around age 40-45.)

Not just cataracts. Have them check for macular degeneration, too, which if I understand correctly can also make your vision dark. (For that matter, have them check for glaucoma while you're in there.)

But I have a question. Is it just the monitor? Or do you notice the same thing with daylight? Room lights?

Mostly monitors. I do need glasses for day to day life, but I don’t feel like it’s dim out there or anything.

backlights do fade; perhaps look at a new monitor to compare?