title: Corneal biomechanical properties measured with the Ocular Response Analyser in a myopic population.
abstract: OBJECTIVE
  To explore the possible association between myopia and corneal biomechanical properties in a Caucasian population, and the correlations between the properties of right and left eyes.
  
  
  METHODS
  Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using the Ocular Response Analyser (ORA) in both eyes of 95 normal adult subjects aged between 19 and 48 years. The spherical equivalent refractive errors of the participants ranged from 0.25 to -14.00 D. The mean CH and CRF values for the right and left eyes were recorded for each subject. CH and CRF data were compared between different refractive groups.
  
  
  RESULTS
  CH was found to be slightly lower in high myopes (>-6.00 D, mean CH 10.0 ± 1.2 mmHg) in comparison to moderate myopes (>-3.00 to -6.00 D, 10.1 ± 1.4 mmHg) and emmetropes and low myopes (+0.25 to -2.75 D, 10.9 ± 1.5 mmHg). The decrease in CH with the degree of myopia was about 0.13 mmHg per D or roughly 1% per D (r(2) = 0.084, p < 0.001). Inter-subject variations were much greater than any systematic changes. CRF was not correlated with refractive error (r(2) = 0.001, p = 0.66). Although the refractive error was highly correlated between the two eyes (r(2) = 0.89, p < 0.001), CH and CRF showed a lower inter-ocular correlation (r(2) = 0.68, p < 0.001 and r(2) = 0.77, p < 0.001 respectively).
  
  
  CONCLUSIONS
  These findings may indicate that the viscoelastic properties of the cornea are altered to a minor extent in myopia. However, in this normal population, any overall systematic changes in CH and CRF with refractive error were small in comparison with the considerable inter-subject scatter at any level of refraction.
authors: Department of Optics and Optometry, Technological Educational Institute of Athens, Athens, Greece.
authors: Athina
authors: A
authors: Plakitsi
authors: Clare
authors: C
authors: O'Donnell
authors: Marco A
authors: MA
authors: Miranda
authors: W Neil
authors: WN
authors: Charman
authors: Hema
authors: H
authors: Radhakrishnan