DPP4 and Epiphora: Host proteases for S protein: FURIN5, TMPRSS2 and dipeptidyl peptidase 4 (DPP4)18 are expressed in the cornea (Fig. 1a), indicating that it is a potential site for SARS-CoV-2 entrance, in agreement with clinical studies showing infected patients’ epiphora, conjunctival congestion, or chemosis19.