My husband is a dentist (also easy on the eyes

) and I asked him what his patients do and he says he doesn’t know because they are wearing dark glasses and he is wearing loupes that magnify the mouth so his field of vision while working is limited. So I don’t think I really matters to your dentist if your eyes are open or closed it’s whatever you are comfortable with as they know most people are never happy to be in the dental chair to begin with.