This is governed by state laws, but I believe in every state you need a Rx.
But you can get an exam and Rx from an OD (optometrist), and you do not need
to get one from an MD (ophthalmologist). Generally, you are better off going
to an OD for a Rx because they have more experience giving exams (unless you
have a serious eye problem that warrants that you visit an MD).

The optometrist is required by federal law to give you a written Rx (upon
request) that you can take to an optical shop, or you can usually purchase
lenses and frames from your OD.

There are some on-line websites that operate overseas that might let you
order without a Rx.  However, you should be able to get a decent eye exam
from an OD for about $50 (some other services may be extra).

Dear Fidelis,

Not a "dumb question".  But the issue is "custom made" -- and
what you mean by that exactly.

You can get "reading glasses" almost anywhere in the USA -- and
the cost is low.

You can get a written "prescription" from an ophthamologist
or optometrist.

If you wish, you can log onto zenniopical, and type the
numbers in and get your plus-lenses from Zenni.

How you choose to obtain plus lenses for reading
is up to you.

Best,

Otis