POSTN and Alzheimer disease: We measured the concentration of periostin in the tear fluid of 31 patients with allergic conjunctival diseases (atopic keratoconjunctivitis (AKC), seven patients with vernal catarrh (VKC), 17 patients with seasonal allergic conjunctivitis (SAC), 18 healthy subjects, 16 patients with AD without ocular allergic symptoms, and nine patients with allergic rhinitis, and tear periostin concentration increased significantly in patients with allergic conjunctival disease.