Tear Organic Acid Analysis After Corneal Collagen Crosslinking in Keratoconus

Objectives: This study examined changes in the levels of organic acids, which are important tear metabolites, after corneal collagen crosslinking (CXL) treatment for keratoconus. Methods: This prospective, nonrandomized, interventional case series included a single eye from 24 patients who were scheduled to receive CXL treatment (Dresden protocol) for progressive keratoconus. Before CXL treatment and at 6 months after treatment, tears were collected in capillary tubes. The patients were separated into four groups as males, females, and ages 18 years younger and >18 older. The organic acid profiles of the tear samples were analyzed using mass spectrometry. Results: An evaluation was made of 12 females and 12 males with a mean age of 19.20 +/- 4.06 years (range: 12-27 years). The greatest percentage increase in organic acids after CXL treatment was observed for N-acetyl-L-aspartic acid (66% increase). The organic acid showing the greatest decrease was 3-OH butyric acid (61% decrease). A decrease of 46% was found (P=0.263) in the lactic acid/malic acid ratio. Conclusion: Metabolomic studies of tears could facilitate a new and objective process in the follow-up period or in the determination of prognosis after CXL treatment for diseases such as keratoconus, which has a multifactorial etiology.