Correlation Study Between Corneal Topographic and Biomechanical Parameters with Tear Inflammatory Mediator Levels in Keratoconus

Abstract Objective: To analyze the correlations among tear inflammatory mediator concentration, corneal topographic and biomechanical parameters in keratoconus(KC) patients. To assess the potential of tear inflammatory mediators as supplementary biomarkers for early KC diagnosis . Design: Clinical Observational Cross-sectional Study. Methods: 60 KC patients(74 eyes) and 12 healthy volunteers(12 eyes) were enrolled. KC group was further subdivided into six groups: FFKC, KC-1,KC-2, KC-3, Post-KP and Post-CXL.T opographic parameters Mean Keratometry (Km), Central Keratoconus Index (CKI), the Inferior—Superior dioptric asymmetry(IS), Keratometry Index (KI), and Central Corneal Thickness (CCT) were m easured by Pentacam. B iomechanical parameters Belin/Ambrosio Deviation Value (BAD-D), Ambrosio’s Relational Thickness(ARTh), The stress-strain Index(SSI), Corneal speed during the first-degree applanation (A1V), Cord length of the first-degree applanation (A1L), The ratio between the deformation amplitude at the apex(DA-Ratio) and Stiffness parameter at first applanation(SP-A1) were assessed by Corvis ST. Tear inflammatory mediator concentration were quantified by Luminex xMAP ® . Results: (1) In form fruste keratoconus（FFKC） patients, IS and BAD-D showed significant increase compare to healthy volunteers. KC group showed significant increases in Km, CKI, IS, BAD-D and A1V, while ARTh, SSI and A1L were significantly decreased. In Post-KP and Post-CXL group, BAD-D was significantly elevated, but the ARTh value was significantly reduced. (2) There is a significant correlation between t ear inflammatory mediator concentration and biomechanical parameters. (3)Tear levels of IL-6, MMP-1, TIMP-1 and MMP-1/TIMP-1 were significantly elevated in KC group.IL-6 and MMP-1 were elevated in FFKC and KC-1 group. Tear IL-6 level were notably higher in KC-2 group, whereas in KC-3 group, only TIMP-1 showed a significant difference. (4) Abnormalities of IS, KI, CCT, DA-Ratio and TIMP-1 were observed in patients received corneal collagen cross-linking (CXL), but not keratoplasty (KP). Conclusion: (1) IS and BAD-D hold diagnostic value for early detection of KC. (2) After KP and CXL, there are still abnormalities in the biomechanical parameters of BAD-D and ARTh, which may be one of the reasons for the recurrence of keratoconus after surgeries. (3) In early KC, tear levels of IL-6 and MMP-1 show significant changes that strongly correlated with corneal biomechanical parameters, indicating their potential as biomarkers for early diagnosis.