LTF and dry eye syndrome: For example, albumin and actin were used as biomarkers of cancers in dogs [12], and alpha fetoprotein was used as a tumor-specific biomarker (for example, in hepatocellular carcinoma) in humans [26], while lactoferrin and lysozyme were used as biomarkers of mucosal immune competence in humans [27], and lipocalin-1 was a candidate as a biomarker of dry eye syndrome [8], etc. Consequently, the findings of this study can be used to establish a proper tear collection method for any tear protein biomarkers in the future.