Keratoconus (KC) is the most common primary corneal ectatic disease which has considerable importance in public health. Corneal collagen crosslinking (CXL) is a procedure to mitigate progression of KC and reduce demand for corneal transplantation. Although studies have proven the efficacy of CXL regarding corneal shape, none have investigated the effects of CXL on tear biomarkers which are useful tools to understand molecular mechanisms behind CXL. Our purpose was to determine the effect of CXL on tear mediators in patients with KC and analyze associations with corneal changes. Tear samples were collected pre-CXL from 26 eyes of 23 patients and during a 12-month follow-up. The mediators’ concentration was measured by Cytometric Bead Array technology. Corneal topography parameters measured by Scheimpflug Camera included: Thinnest-corneal-thickness (ThCT), keratometry values (K1, K2), Radii-Minimum (Rmin), Keratoconus-Index (KI), Center-KI (CKI), Index-of-Height Asymmetry (IHA) and Index-of-Surface Variance (ISV). At baseline, KI was correlated negatively with chemokine (C-C motif) ligand 5 (CCL5) (p=0.015) and matrix metalloproteinase (MMP)-13 (p=0.007). At day 4, interleukin (IL)-6 and IL-8 increased, while IL-13, IL-17A, interferon (IFN)-γ, CCL5, MMP-13, epidermal growth factor (EGF), nerve growth factor (NGF) and plasminogen activator inhibitor (PAI-1) decreased significantly compared to pre-CXL concentrations (p≤0.02). At 6 months tissue plasminogen activator (t-PA) increased (p=0.02), while at 12 months Rmin increased (p≤0.004), and IL-6 and CXCL8 (p=0.005 and p=0.047) as well as K1, ISV and KI decreased. After 6 months CKI and ISV showed significant associations with IL-17A; CKI with IL-13 and ThCT with IL-13 (p≤0.02), while at 12 months there were reverse associations between ThCT and IL-6, IL-13, INFγ, CCL5 and PAI-1 (p≤0.02). Alterations of mediators in tear fluid after CXL associate with topographic changes highlight the fact that many mediators are involved in the complex mechanisms after CXL. Further studies on biomarkers to investigate the efficacy of CXL are needed.

Purpose: To study the association between different types of mediators in the tear fluid and topographic indices characterizing the severity of keratoconus (KC). Methods: In this study, nonstimulated tear fluid samples were collected from 14 eyes of 11 patients with KC. The following indices were measured by corneal topography: maximum K value, average K value, Klyce/Maeda keratoconus index (KCI), Smolek/Klyce keratoconus severity index, opposite sector index, center/surround index, keratoconus prediction index and standard deviation of corneal power. The concentrations of interleukin (IL)-6, IL-13, CXCL8 (IL-8), chemokine (C-C motif) ligand 5 (CCL5, regulated and normal T cell expressed and secreted), matrix metalloproteinase-9 (MMP-9), MMP-13, tissue inhibitor of metalloproteinase-1, nerve growth factor (NGF) and epidermal growth factor were measured by cytometric bead array technology. Release of mediators was calculated from their concentrations and the volume of tears collected over 2 min. Results: Significant positive associations were found between CCL5, MMP-13 and NGF and several topographic indices. Significant negative correlations were found between IL-6 and KCI. Age-dependent associations were observed between IL-13, CXCL8, CCL5 and MMP-13 and the topographic data. Conclusion: Several correlations were observed between the mediators and the topographic indices, suggesting possible roles in the pathophysiology of KC. Our data indicate that some mediators have different effects on the severity of disease in an age-dependent manner.

The release of different cytokines and mediators in tears of patients with keratoconus (KC) wearing contact lenses (CLs) may contribute to the pathology of KC. Cohort study was established in patients with KC wearing rigid gas permeable (RGP) CL (group I), patients with ametropia wearing silicone hydrogel (Si-Hi) CL (group II) and ametropic patients wearing RGP CL (group III). Our findings indicate that before CL wear, the release of epidermal growth factor (EGF) and tissue-type plasminogen activator (t-PA) was attenuated, whereas matrix metalloproteinase (MMP)-9, interleukin (IL)-6, chemokine (C-C motif) ligand 5 (CCL5), IL-13, and plasminogen activator inhibitor (PAI)-1 were enhanced in KC compared with ametropes. An increasing linear trend over time was found for MMP-9, EGF, and CXCL8 in KC and MMP-9, MMP-13, IL-6, and CXCL8 in group III. Significant differences were observed in the linear trend over time between groups I and III for MMP-13 and tissue inhibitor of metalloproteinases (TIMP)-1; between groups I and II for MMP-9 and CXCL8; and between groups III and II for MMP-9, CXCL8, and MMP-13. In KC, the release of MMP-9 at week 6 and nerve growth factor (NGF) at 10 min was higher, but NGF at week 2 was lower than that in group II. The release of MMP-13 and NGF at week 2 and 6 were lower in the KC group as compared with group III, and similarly, with IL-6 and CXCL8 at week 2 and PAI at all time points. Contact lens wear can influence the levels and dynamics of various mediators in the tears of patients with KC that might have an impact on the progression of the disease.

Our purpose was to prospectively analyze the age-related changes of corneal Scheimpflug parameters in healthy subjects. Thirty-five eyes of 35 volunteers (age 14–67 years) were investigated with an average interval of 3.6 years. Changes of corneal parameters (flattest keratometric reading at anterior (K1F) and posterior surface (K1B), steepest keratometric reading at anterior (K2F) and posterior surface, anterior astigmatism, posterior astigmatism (AstigB), flat axis of anterior and posterior astigmatism (AxisB), thinnest pachymetric value (PachyMin), corneal volume (CV10-mm)) were analyzed. K1F and K2F decreased significantly during observation and showed stronger decrease in younger than in older individuals. Higher values proved to be more stable. K1B decreased significantly and the degree of decrease was dependent on its baseline value and age: in young subjects low values increased, high values decreased. AstigB decreased significantly and showed a baseline-dependent significant increase from lower and a significant decrease from higher initial values. Over time, the mean AxisB shifted significantly. PachyMin and CV decreased significantly with age, especially from higher baseline values in younger subjects. The results of this longitudinal study suggest that both corneal surfaces change significantly with age. We demonstrate for the first time that age and baseline values influence age-related changes of corneal parameters.

Objective: To determine the levels of interleukin 6 (IL-6) and interleukin 8 (IL-8/CXCL-8) in tears collected from the eyes of normal individuals and of patients with different irritative eye diseases, in order to acquire information on the immunological changes occurring during the early postoperative period following various forms of eye surgery, including penetrating keratoplasty (PKP). Methods: IL-6 and IL-8 levels were measured with the aid of human ultrasensitive ELISA kits in the non-stimulated tears of patients in the early postoperative period following PKP or cataract operation, and of patients with acute bacterial conjunctivitis or with a corneal foreign body. The IL-6 and IL-8 concentrations, the total amounts released in a given time and the rates of their release were calculated. Results: A significant increase in IL-6 release was observed in all patient groups compared with the normal controls (p ≤ 0.003). The IL-8 release levels were significantly higher in the tears of all patient groups (p ≤ 0.03), except for the cataract operation group, where the IL-8 release was not significantly higher (p = 0.053) than in the control samples. No significant differences in IL-6 or IL-8 release were observed when the various patient groups were compared with each other. Conclusion: The release of IL-6 and IL-8 into the tears is enhanced in various anterior segment eye diseases, and this may be used as an indicator of various inflammatory reactions in the early postoperative period.

Purpose: To find immunomediator combinations which could sensitively indicate keratoconus progression. Methods: Tear samples of 42 patients with keratoconus were collected at baseline and at the end of a one-year follow-up. The concentrations of 13 mediators were measured by CBA. Based on Pentacam HR examination, eyes were divided into a non-progressive and a progressive group. Results: At the end of the follow-up, significant differences were observed in the release of IFNγ, IL-13, IL-17A, CCL5, MMP-13 and PAI-1 between the two groups. Changes in five Pentacam parameters correlated positively with changes in IFNγ, IL-13, IL-17A, CXCL8, CCL5, TIMP-1 and t-PA. We found that tear level of IL-13 in combination with NGF can predict the progression of keratoconus with 100% specificity and 80% sensitivity. Conclusion: The findings of our longitudinal study may underscore the importance of NGF and IL-13 tear levels in the prediction of keratoconus progression.