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Michael Haustein, Eberhard Spoerl, Lutz E Pillunat; Calculation of a Keratoconus Match Index for CorVis ST. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3729.
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© ARVO (1962-2015); The Authors (2016-present)
Keratoconus Match Index (ORA-KMI) of the Ocular Response Analyzer (ORA, Reicherts®, Heidelberg, Germany) is an useful tool to evaluate keratoconus diagnosis, staging and its progression. CorVis ST (Oculus Inc.®; Wetzlar, Germany) is a newer device to observe non-invasively the biomechanical response of the cornea. The aim was to calculate a Keratoconus Match Index (Cor-KMI) for CorVis ST.
In this prospective study we observed 74 right eyes of 48 healthy volunteers and 26 patients with corneal ectatic disease. All eyes underwent an examination with ORA and CorVis ST. The KMI generated by ORA were correlated with the parameters of CorVis ST. Additionally, multiple regression analysis was used to evaluate a formula to calculate a Match Index of CorVis ST (Cor-KMI). SSPS® programm, Spearman correlation and multiple linear regression analysis were used for statistics.
ORAs KMI correlates with these CorVis parameters: IOP (R=0.320; P=0.007), CCT (R=0.639; P<0.001), time at first applanation (A1t) (R=0.313; P=0.008), length at first applannation (A1L) (R=0.288; P=0.014), velocity at second applanation (A2v) (R=0.308; P=0.010), and Wmaxr (R=0.507; P<0.001). These parameters were used for multiple linear regression analysis to calculate Cor-KMI. Cor-KMI= 0.087 x Wmaxr + 0.006 x CorCCT - 3.13 (square R=0.444 P=0.001)
ORA-KMI and Cor-KMI are useful to support differentiation between keratectatic corneal diseases and normal eyes. The diagnostic importance of these novel indexes needs to be further explored.
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