Outcome of Corneal Collagen Cross-Linking in Keratoconus: Introducing the Predictive Factors

PURPOSE: To evaluate the multiple pretreatment characteristics and topographic factors of keratoconus (KC) patients and their relationship to clinical outcomes of corneal collagen cross-linking (CXL). METHODS: In this prospective study, 61 patients (106 eyes) with KC as candidates for CXL were included. Demographic data including age, sex, place of birth and residence, atopic constitution, family history, rubbing history, sleep apnea, and blood group were collected via a structured checklist. Complete ophthalmologic examination and tear collection to assess tear interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) level were performed. Topometric parameters were evaluated using a rotating Scheimpflug topography device. Changes in best corrected visual acuity (BCVA) and maximum keratometry (K-max) were considered the main predicted variables. Predictive variables were analyzed by univariate and multivariate regression. RESULTS: The use of multivariate analysis changes in K-max was significantly associated with rubbing frequency (coefficient = 0.94, P = 0.02), blood group (coefficient = 4.52, P = 0.005), pretreatment corneal asphericity (coefficient = −3.99, P ≤ 0.001), and pretreatment central keratoconus index (CKI) (coefficient = −55.38, P = 0.001). Regarding the changes in BCVA, the multivariate analysis showed a significant association with place of birth (coefficient = −0.08, P = 0.03), pretreatment BCVA (coefficient = −0.67, P < 0.001), pretreatment central corneal thickness (CCT) (coefficient = −0.005, P = 0.04), and pretreatment keratoconus index (KI) (coefficient = 0.53, P = 0.04). Other parameters assessed in the multivariable analysis did not appear to have an individual effect on treatment outcomes. CONCLUSION: Our results demonstrated that blood group, rubbing of eye, place of birth, corneal asphericity, pretreatment BCVA, CKI, KI, and CCT were statistically associated with the outcome of KC following CXL.