- Journal of Refractive Surgery
- March 2011 - Volume 27 · Issue 3: 209-215
To compare corneal hysteresis (CH) and corneal resistance factor (CRF) in eyes with keratoconus with a central corneal thickness (CCT) ≥520 μm with CH and CRF in matched controls, and to estimate the sensitivity and specificity of these parameters for discriminating between the two groups.
This prospective, comparative case series comprised 19 eyes of 19 patients with keratoconus with CCT ≥520 μm and 19 eyes of 19 healthy sex-, age-, and CCT-matched patients who underwent a complete clinical eye examination, corneal topography, tomography, and biomechanical evaluation. The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized the sensitivity and specificity for discriminating between groups.
Central corneal thickness was 543.1±13.9 μm (range: 520 to 568 μm) in the keratoconus group and 545±12.5 μm (range: 527 to 575 μm) in the control group (P=.6017). Corneal hysteresis was 9.22±1.44 mmHg (range: 6.2 to 11.35 mmHg) in the keratoconus group and 10.58±1.91 mmHg (range: 7.34 to 13.53 mmHg) in the control group (P=.0075). Corneal resistance factor was 8.62±1.52 mmHg (range: 5.60 to 11.20 mmHg) in the keratoconus group and 10.30±1.92 mmHg (range: 6.95 to 14.12 mmHg) in the control group (P=.0049). The ROC curve analyses showed a poor overall predictive accuracy of CH (cutoff, 9.90 mmHg; sensitivity, 78.9%; specificity, 63.2%; test accuracy, 71.05%) and CRF (cutoff, 8.90 mmHg; sensitivity, 68.4%; specificity, 78.9%; test accuracy, 73.65%) for detecting keratoconus in the eyes studied.
Corneal hysteresis and CRF were statistically lower in the keratoconus group compared with the control group. Given the large overlap, both CH and CRF had low sensitivity and specificity for discriminating between groups.
From the Department of Ophthalmology, Federal University of Sao Paulo (Fontes, Nosé); Centro de Microcirurgia e Diagnóstico (Fontes), REFRACTA – RIO (Fontes, Ambrósio), Renato Ambrósio Eye Institute (Ambrósio), and Fluminense Federal University (Velarde), Rio de Janeiro, Brazil.
Dr Ambrósio is a consultant for Oculus Optikgeräte GmbH, Wetzlar, Germany, and Reichert Ophthalmic Instruments, Depew, New York. The remaining authors have no proprietary interest in the materials presented herein.
Correspondence: Bruno M. Fontes, MD, Av das Acacias 150 bl 2 apto 1001, Barra da Tijuca, Rio de Janeiro – RJ, 22776-000, Brazil. Tel/Fax: 21 3151 3599; E-mail: firstname.lastname@example.org
Received: November 12, 2009
Accepted: April 07, 2010
Posted Online: May 03, 2010