Official ESCRS | European Society of Cataract & Refractive Surgeons


Evaluation of Corvis biomechanical index for diagnosing forme fruste keratoconus

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Session Details

Session Title: Presented Poster Session: Corneal Cross-Linking

Venue: Poster Village: Pod 3

First Author: : S.Shiga JAPAN

Co Author(s): :    T. Kojima   T. Nishida   T. Nakamura   A. Hasegawa   T. Kaga   K. Ichikawa        

Abstract Details


Keratoconus (KC) is a bilateral progressive corneal disease. Ever since corneal crosslinking has been performed as a therapy to prevent progression, the importance of early detection of KC has drawn attention. Corvis biomechanical index (CBI) is a useful parameter for diagnosing KC. Forme fruste keratoconus (FFK) is defined as a cornea with no abnormalities, as assessed by slit-lamp examination and corneal topography, with the fellow eye of KC. Since FFK is a precursor stage of KC, early diagnosis of FFK is essential. We evaluated the predictive accuracy and biomechanical parameters of CBI for distinguishing FFK eyes from normal eyes.


We included 100 eyes of 54 participants with normal cornea (normal group; 28 men and 26 women; average age, 27.6±6.7 years; mean corneal power, 43.0±1.2 D) and 23 eyes of 23 patients with FFK (FFK group; 18 men and 5 women; average age, 22.0±8.5 years; mean corneal power, 48.2±4.5 D).


The cornea was defined as normal when it met both the judgment by the cornea specialist and the Keratoconus index at 0% in both a corneal topographic and tomographic examination. The CBI and other biomechanical parameters were measured using CorvisST (OCULUS). Based on the ROC curve, the sensitivity and specificity of FFK diagnosis were calculated with a cut-off value of 0.0145. In addition, we compared the biomechanical parameters between the normal group and FFK group. A Mann-Whitney test was performed to compare values between the two groups, and a p value less than 5% was considered statistically significant.


The CBI value was significantly higher in the FFK group (0.36 ± 0.37) than in the normal group (0.06 ± 0.09) (p = 0.004). The sensitivity and specificity in the evaluation group were 82.6% and 74.0%, respectively. The area under the ROC curve was 0.853. There was a significant difference in the DA ratio (2 mm), Ambrosio relational thickness to the horizontal profile (ARTh), and stiffness parameter-A1 between the FFK and normal groups (p = 0.0004; 0.019; <0.0001, respectively).


The current report revealed that the biomechanical properties in FFK eyes were lower than those in normal eyes. The CBI was shown to be highly sensitive and specific for distinguishing FFK eyes from normal eyes. This means that the CBI can detect KC before any changes in corneal topography. We believe that CBI is a promising screening parameter, and by using it, we can treat KC at the appropriate time and prevent progression.

Financial Disclosure:


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