title: Effect of diabetes mellitus on Corvis ST measurement process.
abstract: OBJECTIVE
  Diabetes mellitus (DM) affects corneal biomechanical parameters. We compared analyses using ORA (Ocular response analyser) and Corvis ST to determine the influence of disease duration, hyperglycaemia and haemoglobin A1c (HbA1c) levels on these parameters.
  
  
  METHODS
  This observational, cross-sectional, observer-masked study assessed one eye of 94 consecutive DM patients and 41 healthy subjects. Two DM groups were analysed: the uncontrolled DM group (n = 54) (HbA1c ≥ 7%) and the controlled DM group (n = 40) (HbA1c < 7%). Central corneal thickness (CCT) was measured by ultrasonic pachymetry and intraocular pressure (IOP) by Goldmann applanation tonometry. ORA and Corvis ST analyses were performed to evaluate the changes.
  
  
  RESULTS
  Most of the Corvis ST parameters [Deformation amplitude (DA), A1 and A2 times, A1 velocity] in the uncontrolled DM group eyes were found to be significantly different to controls and controlled DM group eyes (p = 0.005, p = 0.001, p < 0.0001, p = 0.002, respectively). DA on the Corvis ST was correlated with blood glucose concentration (p = 0.004) and HbA1c percentage (p = 0.002). ORA corneal hysteresis was significantly lower in diabetic patients with elevated HbA1c than in control subjects (p = 0.001) and was affected by disease duration (p = 0.037), whereas the corneal resistance factor remained unaltered.
  
  
  CONCLUSIONS
  A poor glucose control in DM affects corneal biomechanics measured by ORA and Corvis ST, which may cause high IOP measurements independent of CCT. The measurement of the corneal biomechanics should be taken into consideration in the clinical practice.
authors.affiliation: Department of Ophthalmology, University Hospital Principe de Asturias, University of Alcalá, Alcalá de Henares, Madrid, Spain.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Pérez-Rico
authors.forename: Consuelo
authors.initials: C
authors.lastname: Gutiérrez-Ortíz
authors.forename: Ana
authors.initials: A
authors.lastname: González-Mesa
authors.forename: Asunción M
authors.initials: AM
authors.lastname: Zandueta
authors.forename: Agustín
authors.initials: A
authors.lastname: Moreno-Salgueiro
authors.forename: Francisco
authors.initials: F
authors.lastname: Germain
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001786:Blood Glucose / Q000378:metabolism; D003315:Cornea / Q000503:physiopathology*; D063171:Corneal Pachymetry; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000503:physiopathology*; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D014065:Tonometry, Ocular
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: corneal biomechanical properties; corneal deformation amplitude; diabetes mellitus; ocular response analyser