If really is dry eye syndrome (keratocongiuntivitis sicca) it is often sufficient to use Hypromellose eye drops 0.3% (no added agents) and it resolves quickly. Being often constitutional it will come back 3-4 times a year, and you will use the drops again.
I do not believe in Functional Medicine, I think is pseudoscientific silly medicine.
You will need to see a specialist only if:
a- you also have blepharitis (inflammation of the eyelids)
b- if you are on antidepressants, beta-blockers, allergy pills, diuretics. These in some patients can give dry eye
c- in pregnancy, with contraceptive pill
If instead it is Sjogren's syndrome, then it is a different matter all together
BWs
Franco