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Maxime Delbarre, Mikhael Lussato, Catherine Verret, Bénédicte Blavier, Corinne Leduc, Pascale Crepy, Françoise Froussart-Maille, Jean Claude Rigal-Sastourné; Keratoconus Match Index of normal and keratoconus suspect eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1118.
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© ARVO (1962-2015); The Authors (2016-present)
To compare Keratoconus Match Index (KMI) of the Ocular Response Analyser between keratoconus, forme fruste keratoconus and normal corneas and estimate the sensitivity and the specificity of KMI in discriminating forme fruste keratoconus from healthy corneas.
The study population of this retrospective comparative case series was divided into 3 groups: 24 keratoconic (KCN) eyes (16 patients), 8 forme fruste keratoconic eyes (FFKCN, normal topography with controlateral KC), and 36 healthy eyes (18 patients). Every patient underwent a complete clinical eye examination, a corneal topography, and a biomechanical evaluation with the Ocular Response Analyser (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA). Corneal hysteresis (CH), corneal resistance factor (CRF), and KMI were compared between the 3 groups. The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized sensitivity and specificity in discriminating FFKCN from normal corneas.
The mean KMI was 0.20 for KCN, 0.67 for FFKCN and 0.928 for control eyes. There was a statistically significant difference between the 3 groups (P < 0.001) and also between the FFKCN group and the control group (P = 0.05). The mean CH was 7.31 mmHg for KCN, 9.21 mmHg for FFKCN and 10.8 mmHg for control eyes (P < 0.001). The mean CRF was 6.29 mmHg for KCN, 8.18 mmHg for FFKCN and 10.6 mmHg for control eyes (P < 0.001). For a threshold of 0,8, KMI had a sensitivity of 63% with a specificity of 72%. For a threshold of 10,7mmHg, the CH had a sensitivity of 75% and a specificity of 66,7%.
There is a significant difference in the mean KMI between normal and FFKCN corneas. Sensitivity and specificity of this index are not greater than those of CH and CRF. KMI seems to be useful for the detection of FFKCN but further studies with bigger samples are necessary.
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