• Bernava, Giuseppe Massimo
• Lombardo, Marco
• Alunni-Fegatelli, Danilo
• Roszkowska, Anna Maria
• Serrao, Sebastiano
• Mencucci, Rita
• Vestri, Annarita
• Lombardo, Giuseppe
• Aleo, Danilo

Abstract

<jats:sec><jats:title>Purpose:</jats:title><jats:p>The aim of this study was to assess accuracy of the <jats:italic toggle="yes">mean corneal stiffness</jats:italic> (<jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub>, N/m) parameter to discriminate between patients with keratoconus and age-matched healthy subjects.</jats:p></jats:sec><jats:sec><jats:title>Methods:</jats:title><jats:p>Dynamic Scheimpflug imaging tonometry was performed with Corvis ST (Oculus Optikgeräte GmbH, Germany) in patients with keratoconus (n = 24; study group) and age-matched healthy subjects (n = 32; control). An image processing algorithm was developed to analyze the video sequence of the Corvis ST air-puff event and to determine the geometric and temporal parameters that correlated with the corneal tissue biomechanical properties. A modified 3-element viscoelastic model was used to derive the <jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub> parameter, which represented the corneal tissue resistance to deformation under load. Receiver operating characteristic curves were used to assess the overall diagnostic performance for determining the area under the curve, sensitivity, and specificity of the <jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub> in assessing the corneal tissue deformation to the Corvis ST air-puff event in keratoconus and control eyes. The <jats:italic toggle="yes">Corvis Biomechanical Index</jats:italic> (<jats:italic toggle="yes">CBI</jats:italic>) was analyzed for external validation.</jats:p></jats:sec><jats:sec><jats:title>Results:</jats:title><jats:p>The <jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub> parameter was significantly different between keratoconus and controls (<jats:italic toggle="yes">P</jats:italic> &lt; 0.001), ranging from 24.9 ±3.0 to 34.2 ±3.5 N/m, respectively. It was highly correlated with <jats:italic toggle="yes">CBI</jats:italic> (r = −0.69; <jats:italic toggle="yes">P</jats:italic> &lt; 0.001); however, the <jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub> parameter had greater specificity (94%) than <jats:italic toggle="yes">CBI</jats:italic> (75%), whereas the 2 biomarkers had similar area under the curve (0.98 vs. 0.94) and sensitivity (96% vs. 92%) in predicting the occurrence of keratoconus.</jats:p></jats:sec><jats:sec><jats:title>Conclusions:</jats:title><jats:p>The <jats:italic toggle="yes">k</jats:italic><jats:sub>c</jats:sub> parameter extracted by video processing analysis of dynamic Scheimpflug tonometry data was highly accurate in discriminating patients with clinically manifest keratoconus compared with controls.</jats:p></jats:sec>

Topics

• size-exclusion chromatography