title: Biomechanical properties of early keratoconus: Suppressed deformation signal wave.
abstract: OBJECTIVE
  To examine the diagnostic validity of different corneal biomechanical parameters for the detection of early keratoconus METHODS: Sixty-one eyes with a diagnosis of early keratoconus and 61 topographically normal eyes were enrolled in the study. All participants underwent testing with the Ocular Response Analyzer (ORA), and 40 indices from each cornea were included in the analysis.
  
  
  RESULTS
  The mean (standard deviation: SD) of keratometry and central corneal thickness in keratoconic corneas was 46.9 (2.5) diopter (D) and 473 (31) μm, respectively. Of the 40 evaluated indices, 32 showed a significant difference between the two groups using t-test (p<0.05). According to the results of logistic regression, the indices of height from the lowest to the highest point in peak 2 (H21) and corneal resistance factor (CRF) with R2=0.79 were the best predictors of early keratoconus (p<0.001). H21≤190 with a sensitivity and specificity of 87% and 91.8%, respectively, and CRF≤8.6 with sensitivity and specificity of 87% and 85.3%, respectively, yielded an overall diagnostic accuracy of 97.3%.
  
  
  CONCLUSIONS
  This study results point to the important role of novel waveform-derived indices measured by ORA, along with conventional biomechanical indices, for the early diagnosis of keratoconus. The best predictors of keratoconus in its early stages are H21and CRF which showed very high sensitivity and specificity for the detection of early keratoconus.
authors.affiliation: Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.affiliation: Health and Nutrition Research Center, Lorestan University of Medical Sciences, Khoramabad, Iran.
authors.forename: Asghar
authors.initials: A
authors.lastname: Beiranvand
authors.affiliation: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Abbasali
authors.initials: A
authors.lastname: Yekta
authors.affiliation: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Asharlous
authors.affiliation: Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Electronic address: khabazkhoob@yahoo.com.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
mesh_terms: D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D004548:Elasticity / Q000502:physiology*; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D007640:Keratoconus / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D012372:ROC Curve; D042262:Retinoscopy; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: Biomechanical properties; Keratoconus; Ocular response analyzer