An interesting thing I heard from my dentist and my optometrist is that dentists and optometrists often diagnose (or successfully refer for) a fairly wide variety of conditions that manifest as symptoms visible in the gums and eyes. A lot of stuff that can go wrong in the body can apparently mess up your gums or eyes in a way that an expert can notice.
Also, people who have excellent vision can still benefit from optometrist exams because they can catch early stages of eye problems, and even other kinds of medical problems.
High blood pressure will not always be accompanied by easily detectable symptoms like audible thumping. There's a reason why it's called "the silent killer." (See: https://www.cdc.gov/bloodpressure/index.htm).