title: Corneal biomechanics in asymmetrical normal-tension glaucoma.
abstract: OBJECTIVE
  We aimed to assess corneal biomechanics using the ocular response analyzer in patients with normal-tension glaucoma (NTG), and to evaluate the relationship between corneal biomechanics and visual field loss.
  
  
  METHODS
  This was a prospective observational case series including patients with bilateral asymmetric NTG. For all patients, corneal hysteresis (CH), corneal resistance factor (CRF), CH - CRF difference, and central corneal thickness values were matched against the mean deviation (MD) of the visual field and the cup/disc ratio. For paired-eye comparison in each patient, both eyes were categorized into a better-eyes group and a worse-eyes group according to lower and higher corneal-compensated intraocular pressure readings, respectively. Statistical analysis was carried out with the independent-samples Student's t-test, and the level of statistical significance was set at 0.05. Correlation was assessed using Pearson's correlation coefficient.
  
  
  RESULTS
  The study included 240 eyes of 120 patients. CH was inversely proportional to the MD in the visual field (P=0.01). CRF in both eyes was inversely proportional to the MD of the visual field (P=0.01). CH - CRF difference was directly proportional to the MD of the visual field (P=0.01). For paired-eye comparison, lower corneal-compensated intraocular pressure was associated with higher CH, higher CRF, smaller cup/disc ratio, and less deterioration of MD of visual field.
  
  
  CONCLUSIONS
  CH, CRF, and CH - CRF are more powerful predictors of NTG progression than central corneal thickness.
authors.affiliation: Department of Glaucoma and Optic Nerve Diseases, Research Institute of Ophthalmology, Cairo, Egypt.
authors.forename: Hazem
authors.initials: H
authors.lastname: Helmy
authors.affiliation: Retina Department, Research Institute of Ophthalmology, Cairo, Egypt.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Leila
authors.affiliation: Corneal Diseases Department, Research Institute of Ophthalmology, Cairo, Egypt.
authors.forename: Ahmed Atef
authors.initials: AA
authors.lastname: Zaki
keywords: corneal hysteresis; corneal resistance factor; corneal-compensated intraocular pressure