title: Corneal hysteresis in patients with glaucoma-like optic discs, ocular hypertension and glaucoma.
abstract: BACKGROUND
  To compare corneal hysteresis (CH) measurements between patients with glaucoma, ocular hypertension (OHT) and glaucoma-like optic discs (GLD)- defined as a cup to disc ratio greater than or equal to 0.6 with normal intraocular pressure (IOP) and visual fields. The secondary aim was to investigate whether corneal resistance factor (CRF) and central corneal thickness (CCT) differ between patient groups.
  
  
  METHODS
  In this cross sectional study a total of 123 patients (one eye each) were recruited from a glaucoma outpatient department to undergo ocular response analyser (ORA) testing and ultrasound pachymetry as well as clinical examination. A One-way Analysis of Covariance (ANCOVA) was conducted to evaluate the mean difference in CH between the three diagnostic groups (glaucoma, OHT and GLD) correcting for potential confounding factors, IOP and age. Analysis was repeated for CRF and CCT.
  
  
  RESULTS
  There was a significant difference in mean CH across the three diagnosis groups; F(2, 115) = 96.95; p < 0.001. Mean CH significantly higher for GLD compared to glaucoma (mean difference 1.83, p < 0.001), and significantly higher for OHT compared to glaucoma (mean difference 2.35, p < 0.001). Mean CH was slightly lower in patients with GLD than those with OHT but this difference was not statistically significant. A similar pattern was seen when the analysis was repeated for CRF and CCT.
  
  
  CONCLUSIONS
  Higher CH in GLD and OHT compared to glaucoma suggests increased viscoelasticity of ocular tissues may have a protective role against glaucoma.
authors.affiliation: School of Medicine and Medical Sciences, Mater Misericordiae University Hospital, Eccles Street Dublin 7, Dublin, Ireland. murphm24@tcd.ie.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Murphy
authors.affiliation: School of Medicine and Medical Sciences, Mater Misericordiae University Hospital, Eccles Street Dublin 7, Dublin, Ireland.
authors.forename: Olya
authors.initials: O
authors.lastname: Pokrovskaya
authors.affiliation: School of Medicine and Medical Sciences, Mater Misericordiae University Hospital, Eccles Street Dublin 7, Dublin, Ireland.
authors.forename: Marie
authors.initials: M
authors.lastname: Galligan
authors.affiliation: School of Medicine and Medical Sciences, Mater Misericordiae University Hospital, Eccles Street Dublin 7, Dublin, Ireland.
authors.forename: Colm
authors.initials: C
authors.lastname: O'Brien
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D003315:Cornea / Q000473:pathology / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004548:Elasticity / Q000502:physiology*; D005260:Female; D005901:Glaucoma / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000473:pathology / Q000503:physiopathology*
keywords: Central corneal thickness; Corneal hysteresis; Corneal resistance factor; Glaucoma-like optic discs; Ocular response analyser