title: Association between diabetes and keratoconus: a case-control study.
abstract: OBJECTIVE
  To compare the prevalence and association of diabetes mellitus (DM) between keratoconus (KC) and non-KC populations and evaluate whether DM has the potential to protect the cornea against developing keratectasia.
  
  
  METHODS
  A retrospective case-control study was conducted on 1383 KC patients and 1383 non-KC controls. The presence or absence of either type 1 or type 2 DM was investigated in both groups. Statistical significance and odds ratios were calculated.
  
  
  RESULTS
  The prevalence of DM in KC patients and the control group was 0.8% and 2.2%, respectively. Statistical analysis revealed a strong protective effect of DM against KC (odds ratio = 0.350, P = 0.001). This effect was only seen in type 2 DM patients (odds ratio = 0.079, P < 0.001) and not in patients with type 1 DM (odds ratio = 3.013, P = 0.073).
  
  
  CONCLUSIONS
  The results of this study suggest that DM provides a statistically significant protective effect against the development of KC. This investigation showed that the biomechanical effects of cross-linking were also reflected in epidemiological results.
authors.affiliation: *Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran; and †School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Naderan
authors.forename: Morteza
authors.initials: M
authors.lastname: Naderan
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Rezagholizadeh
authors.forename: Masoome
authors.initials: M
authors.lastname: Zolfaghari
authors.forename: Rozhin
authors.initials: R
authors.lastname: Pahlevani
authors.forename: Mohammad Taher
authors.initials: MT
authors.lastname: Rajabi
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D055815:Young Adult