title: Tear Film and Serum Prolidase Activity and Oxidative Stress in Patients With Keratoconus.
abstract: OBJECTIVE
  To determine and compare the serum and tear film prolidase activity (PA) between patients with keratoconus and healthy subjects. Also, we aimed to evaluate the serum oxidative stress level and the correlation with serum PA in patients with keratoconus.
  
  
  METHODS
  This prospective, comparative clinical study included 31 patients with keratoconus and 33 age-matched and sex-matched control subjects. All participants underwent a detailed ophthalmologic examination. Serum and tear samples were obtained from all participants. Tears and serum PA and serum oxidative stress markers were measured.
  
  
  RESULTS
  No significant differences in demographic characteristics were detected between groups (P > 0.05). The serum PA was significantly lower in the keratoconus group than in the control group (895.6 ± 198.7 vs. 1145.9 ± 285.4 U/L, P < 0.001). A tear film comparison showed that PA was lower in the keratoconus group than in the control group; however, this difference was not significant (3075.4 ± 672.2 vs. 3225.8 ± 903.2 U·L⁻¹·g⁻¹ protein, P = 0.45). Oxidative stress markers, such as total oxidant status and oxidative stress index, were found to be significantly higher in the keratoconus group (P < 0.001).
  
  
  CONCLUSIONS
  The serum PA was found to be lower in patients with keratoconus than in the controls. Additionally, serum oxidative stress markers were found to be higher than those of the controls. Thus, prolidase and systemic oxidative stress may have a role in the pathogenesis of keratoconus.
authors.affiliation: Departments of *Ophthalmology, and †Biochemistry, Faculty of Medicine, Harran University, Sanliurfa, Turkey.
authors.forename: Tuğba
authors.initials: T
authors.lastname: Göncü
authors.forename: Ali
authors.initials: A
authors.lastname: Akal
authors.forename: Fatih Mehmet
authors.initials: FM
authors.lastname: Adıbelli
authors.forename: Sevim
authors.initials: S
authors.lastname: Çakmak
authors.forename: Hatice
authors.initials: H
authors.lastname: Sezen
authors.forename: Ömer Faruk
authors.initials: ÖF
authors.lastname: Yılmaz
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D004150:Dipeptidases / Q000097:blood*; D005136:Eye Proteins / Q000097:blood*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000201:enzymology* / Q000473:pathology; D008297:Male; D018384:Oxidative Stress; D011446:Prospective Studies; D013666:Tears / Q000201:enzymology*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D005136:Eye Proteins; C042434:tear proteins; D004150:Dipeptidases; C022449:proline dipeptidase