title: Ocular Surface Disease Parameters After Collagen Cross-Linking for Keratoconus.
abstract: OBJECTIVE
  To analyze the variations in tear quantity and quality after corneal collagen cross-linking (CXL) in patients with keratoconus.
  
  
  METHODS
  This is a prospective observational study of 24 eyes with keratoconus that underwent epithelium-off CXL. The variables studied were tear film osmolarity, subjective symptoms (Ocular Surface Disease Index), tear breakup time, Schirmer test (SCH) score, tear clearance, fluorescein staining, and lissamine green staining. Variables were determined preoperatively and 3, 6, and 12 months after CXL.
  
  
  RESULTS
  All the studied variables remained stable after 1-year follow-up (no significant difference in comparison with baseline values; Mann-Whitney U test). There was a positive paired correlation between the SCH score and tear clearance at 3; 0.532 (P < 0.01), 6; 0.434 (P = 0.04), and 12 months; 0.675 (P < 0.01). There was no correlation between the SCH score and tear breakup time, apart from a positive correlation at 12 months; 0.601 (P = 0.05). A negative correlation was found between osmolarity and the SCH score at 3; -0.589 (P < 0.01) and 12 months; -0.049 (P = 0.04). The Ocular Surface Disease Index did not correlate with any of the studied variables (Spearman test).
  
  
  CONCLUSIONS
  CXL, at least during the first postoperative year, does not modify the parameters currently used to evaluate tear film function. There is no correlation between objective and subjective parameters in the analysis of the tear film function.
authors.affiliation: *Cornea Department, Instituto Clínico-Quirúrgico de Oftalmología, Bilbao, Spain; †Bioftalmik SL, Derio, Spain; ‡Universidad Europea de Madrid, Villaviciosa de Odon, Spain; and §University of the Basque Country, Bilbao, Spain.
authors.forename: José I
authors.initials: JI
authors.lastname: Recalde
authors.forename: Arantxa
authors.initials: A
authors.lastname: Acera
authors.forename: Iñaki
authors.initials: I
authors.lastname: Rodríguez-Agirretxe
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Sánchez-Tena
authors.forename: Juan
authors.initials: J
authors.lastname: San-Cristóbal
authors.forename: Juan A
authors.initials: JA
authors.lastname: Durán
mesh_terms: D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism*; D019781:Corneal Topography; D003432:Cross-Linking Reagents; D005260:Female; D015590:Fluorophotometry; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011446:Prospective Studies; D012256:Riboflavin / Q000627:therapeutic use*; D013666:Tears / Q000737:chemistry / Q000502:physiology*; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin