Metabolomic analysis identifies alterations of amino acids in the tears and plasma of patients with dry eye disease with ocular pain.

Objectives: Identifying the amino acid in tears and plasma and investigating the correlation between amino acid concentrations and the presence of dry eye disease (DED) with ocular pain. Methods: 15 participants in the DED with ocular pain group, 19 in the DED group, and 16 in the control group were enrolled and underwent DED examinations. Evaluation parameters included the Ocular Surface Disease Index score, Numeric Rating Scale score, clinical ocular parameters, as well as measurements from in vivo laser confocal microscopy. Amino acid concentrations were analyzed using the Waters ACQUITY UPLC I-Class/Xevo TQ-S micro system. Results: A total of 29 and 36 distinct amino acids were identified in tear fluid and plasma, respectively. The results showed significantly higher levels of methionine (MET) in tear fluid and 1-methyl-L-histidine (1-MEHIS) in plasma in people who developed DED with ocular pain compared to those who did not (p = 0.003, q-value = 0.044; p < 0.001, q-value < 0.001), with receiver-operating characteristic analysis yielding an AUC of 0.686 and 0.869. Conclusion: MET in tear fluid and 1-MEHIS in plasma were significantly associated with DED with ocular pain, showing promise as potential biomarkers for DED with ocular pain. Further validation through large-scale studies is warranted.