Corneal Biomechanical Properties in Keratoconic, Myopic, and Hyperopic Eyes as Measured with a Scheimpflugbased Tonometer
Irina S Barequet, Nadav Shoshany, Ran Rutenberg, David Zadok
Cornea, Keratoconus, Scheimpflug based tonometer.,Biomechanical
Citation Information :
Barequet IS, Shoshany N, Rutenberg R, Zadok D. Corneal Biomechanical Properties in Keratoconic, Myopic, and Hyperopic Eyes as Measured with a Scheimpflugbased Tonometer. Int J Kerat Ect Cor Dis 2018; 7 (1):19-25.
Aim: To evaluate corneal biomechanical properties in myopic (MY), hyperopic (HY), and keratoconic (KCN) eyes as measured with the Corvis ST, a newly developed Scheimpflugbased noncontact tonometer with features of visualization and measurement of the corneal deformation response to an air impulse.
Materials and methods: Corneal biomechanical properties measurements were obtained for 34 KCN, 109 MY, and 12 HY patients. Statistical analysis was performed using logistic regression in order to control for confounders (intraocular pressure, pachymetry, and first applanation time) and to identify optimal combinations of parameters for KCN detection.
Results: No single parameter was significantly different between KCN and either MY or HY after controlling for cofounders. The two combinations of parameters that were assessed achieved low specificity and sensitivity values.
Conclusion: The parameters and their combinations overlapped significantly between the groups and could not provide an adequate means to differentiate KCN from healthy corneas. Therefore, with regard to KCN, the Corvis ST can only be used as an adjunct to the clinical examination and customary diagnostic tools.
Johnson RD, Nguyen MT, Lee N, Hamilton DR. Corneal biomechanical properties in normal, forme fruste keratoconus, and manifest keratoconus after statistical correction for potentially confounding factors. Cornea 2011 May;30(5): 516-523.
Hallahan KM, Sinha Roy A, Ambrosio R Jr, Salomao M, Dupps WJ Jr. Discriminant value of custom ocular response analyzer waveform derivatives in keratoconus. Ophthalmology 2014 Feb;121(2):459-468.
Ventura BV, Machado AP, Ambrósio R Jr, Ribeiro G, Araújo LN, Luz A, Lyra JM. Analysis of waveform-derived ORA parameters in early forms of keratoconus and normal corneas. J Refract Surg 2013 Sep;29(9):637-643.
Oculus Optikgeräte GmbH. Corvis ST pocket book. Wetzlar: Oculus Optikgeräte GmbH; 2012. [cited 2012 Jun 28]. Available from: http://www.Oculus.de/en/sites/detail_ger. php?page-597.
Ambrosio R Jr, Alonso RS, Luz A, Coca Velarde LG. Cornealthickness spatial profile and corneal-volume distribution: tomographic indices to detect keratoconus. J Cataract Refract Surg 2006 Nov;32(11):1851-1859.
Madea N, Klyce SD, Smolek MK. Comparison of methods for detecting keratoconus using videokeratography. Arch Ophthalmol 1995 Aug;113(7):870-874.
Lim L, Wei RH, Chan WK, Tan DT. Evaluation of keratoconus in Asians: role of Orbscan II and Tomey TMS-2 corneal topography. Am J Ophthalmol 2007 Mar;143(3):390-400.
Klein SR, Epstein RJ, Randleman JB, Stulting RD. Corneal ectasia after laser in situ keratomileusis in patients without apparent preoperative risk factors. Cornea 2006 May;25(4): 388-403.
Shah S, Laiquzzaman M, Bhojwani R, Mantry S, Cunliffe I. Assessment of the biomechanical properties of the cornea with the ocular response analyzer in normal and keratoconic eyes. Invest Ophthalmol Vis Sci 2007 Jul;48(7):3026-3031.
Ortiz D, Piñero D, Shabayek MH, Arnalich-Montiel F, Alió JL. Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg 2007 Aug;33(8):1371-1375.
Shah S, Laiquzzaman M. Comparison of corneal biomechanics in pre and post-refractive surgery and keratoconic eyes by Ocular Response Analyzer. Cont Lens Anterior Eye 2009 Jun;32(3):129-132.
Fontes BM, Ambrósio R Jr, Jardim D, Velarde GC, Nosé W. Corneal biomechanical metrics and anterior segment parameters in mild keratoconus. Ophthalmology 2010 Apr;117(4): 673-679.
Saad A, Lteif Y, Azan E, Gatinel D. Biomechanical properties of keratoconus suspect eyes. Invest Ophthalmol Vis Sci 2010 Jun;51(6):2912-2916.
Ehlers N, Bramsen T, Sperling S. Applanation tonometry and central corneal thickness. Acta Ophthalmol (Copenh) 1975 Mar;53(1):34-43.
Brandt JD, Gordon MO, Beiser JA, Lin SC, Alexander MY, Kass MA; Ocular Hypertension Treatment Study Group. Changes in central corneal thickness over time: the ocular hypertension treatment study. Ophthalmology 2008 Sep;115(9): 1550-1556, 1556.e1.
Wolffsohn JS, Safeen S, Shah S, Laiquzzaman M. Changes of corneal biomechanics with keratoconus. Cornea 2012 Aug;31(8):849-854.