Any suggestions how to do a vision check for a person with dementia?

Tammy, probably no different then having eye checked for a small child. I would highly sugest you use an ophthalmologist, instead of using staff at store that sells eye glasses.

Opthalmologist can do surgery, and have the latest equipment for checking eyes. Example, there is a computer where one looks into and the computer will let the doctor know what prescription is needed, but the ophthalmologist will double check the results doing hands-on. That may be difficult for hubby to know "which is better, 1 or 2" every time the doctor makes an adjustment on the equipment.

The doctor can also check for cataracts, glaucoma and macular degeneration.

Its hard because they are not able to answer questions but there is a way they can adjust strengths without going thru the full exam. He should have an exam for no other reason than to catch glocoma in its early stages.