title: Optic disc planimetry, corneal hysteresis, central corneal thickness, and intraocular pressure as risk factors for glaucoma.
abstract: OBJECTIVE
  To determine whether corneal hysteresis and central corneal thickness are independent risk factors for glaucoma.
  
  
  METHODS
  A cross-sectional population-based cohort study.
  
  
  METHODS
  Associations were tested between corneal hysteresis, measured in 1754 population-based subjects from the TwinsUK cohort, and glaucoma-related endophenotypes, including intraocular pressure (IOP), vertical cup-to-disc ratio, optic disc area, and optic disc cup area. Corneal hysteresis, IOP, and central corneal thickness (CCT) were measured; optic disc photographs were analyzed; and multivariable linear regression analysis was performed.
  
  
  RESULTS
  Data were available on 1645 individuals. Multiple regression analysis showed corneal hysteresis to be significantly negatively associated with age (beta coefficient = -0.03, P < .00005) and IOP (beta coefficient = -0.06, P < .00005). Corneal hysteresis was also found to be associated with CCT (beta coefficient = 0.02, P < .0005). There was no significant association between corneal hysteresis and optic disc area (P = .6), cup area (P = .77), vertical cup-to-disc ratio (P = .51), or spherical equivalent (P = .08). CCT was also found to be significantly associated with IOP (beta coefficient = 3.3, P < .0005) and corneal hysteresis (beta coefficient = 9.4, P < .0005), but not with age (P = .59) or spherical equivalent (P = .16).
  
  
  CONCLUSIONS
  In this large cohort of healthy British twins, we found no relationship between corneal hysteresis or CCT and quantitative measures of optic disc cupping, suggesting that corneal hysteresis and CCT are not independent risk factors for glaucoma.
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College, London, United Kingdom. Electronic address: francis.carbonaro@btopenworld.com.
authors.forename: Francis
authors.initials: F
authors.lastname: Carbonaro
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College, London, United Kingdom.
authors.forename: Pirro G
authors.initials: PG
authors.lastname: Hysi
authors.affiliation: Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Fahy
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College, London, United Kingdom.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Nag
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College, London, United Kingdom.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hammond
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003315:Cornea / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004548:Elasticity / Q000502:physiology*; D005260:Female; D005901:Glaucoma / Q000209:etiology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D009929:Organ Size; D012042:Registries; D012307:Risk Factors; D055815:Young Adult