The most frequent cause for dry eyes
has to do with the enviroment .
When mouth or other mucosa are effected the problem might be systemic . The diagnosis is a clinical diagnosis and the test are simple, a schirmer test for the eyes , that is done by the eye doctor with a small adsorbent paper and for the mouth the old question of are you able to swallow and chew a cracker with out water . The lab data might help to increase the suspicion of the presence of the disease