title: Age-related variations in corneal biomechanical properties.
abstract: OBJECTIVE
  To determine age-related changes in corneal viscoelastic properties in healthy individuals.
  
  
  METHODS
  This observational cross-sectional study was performed at the Department of Ophthalmology, Imam Khomeini Hospital, Ahvaz, Iran and included 302 healthy individuals in 6 age decades (range: 10-69 years). After complete ocular examination, corneal viscoelastic properties were measured by ocular response analyzer and central corneal thickness (CCT) by an ultrasonic pachymeter. Our main outcome measures were corneal viscoelastic properties in different age groups.
  
  
  RESULTS
  Corneal hysteresis (CH) and corneal resistance factor (CRF) showed a significant negative correlation with age (P < 0.001 for both, r = -0.353 and r = -0.246, respectively). Female gender had significantly higher CH (P = 0.017) and CRF (P = 0.019). CH and CRF were significantly correlated (P < 0.001, r = 0.821). CCT showed a biphasic pattern with significantly higher thicknesses before 20 and after 50 years of age. CH and CRF were significantly correlated with CCT (P < 0.001 for both, r = 0.21 and r = 0.26, respectively) and intraocular pressure (IOP) (P < 0.001 for both, r = -0.474 and r = 0.598, respectively). Corneal-compensated IOP (IOPcc) was significantly higher after age 40 compared to age group <20 (p < 0.045). Goldmann-correlated IOP (IOPg) was significantly correlated with CCT (P = 0.001, r = 0.193), while IOPcc showed no correlation with CCT (P = 0.265, r = 0.062). CH was significantly higher in hyperopic eyes compared to emmetropic eyes (P = 0.009) and myopic eye (P < 0.001).
  
  
  CONCLUSIONS
  In this study, there was a decrease in CH and CRF with an increase in age. Hyperopia and female gender are associated with higher CH and CRF. CCT is higher toward the extremes of life and is significantly correlated with CH and CRF.
authors: Department of Ophthalmology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors: Farideh
authors: F
authors: Sharifipour
authors: Department of Ophthalmology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors: Mahmoodreza
authors: M
authors: Panahi-Bazaz
authors: Department of Ophthalmology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors: Roghayeh
authors: R
authors: Bidar
authors: Iran University of Medical Sciences, Tehran, Iran.
authors: Aida
authors: A
authors: Idani
authors: Department of Biostatics and Epidemiology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors: Bahman
authors: B
authors: Cheraghian
keywords: Aging; Corneal hysteresis; Corneal resistance factor; Ocular response analyzer