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M. Saika, N. Maeda, T. Nakagawa, Y. Hirohara, T. Mihashi, T. Fujikado; The Most Important Factor in Zernike Modes of Corneal Topography on Logistic Regression Using Akaike's Information Criterion (AIC). Invest. Ophthalmol. Vis. Sci. 2009;50(13):5096.
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© ARVO (1962-2015); The Authors (2016-present)
To develop an efficient method to classify pathological corneal surfaces, we evaluated the most important factor in Zernike modes of corneal topography with logistic regression.
For the subjects of 51 keratoconic eyes(KC), 46 keratoconus suspect eyes(KCS), 50 myopic LASIK eyes(L), 20 pellucid eyes(P), and 65 normal eyes(N), a Placido-based videokeratography was performed using a KR-9000PW (Topcon) machine. The corneal wavefront aberrations were analyzed with the 2nd to 4th order Zernike polynomials for a 6-mm diameter circular area. Single-variable logistic regression with two categories, (KC/N, KCS/N, L/N, P/N, KC/P, KCS/P, KC/KCS), was performed. We chose each Zernike term as a variable and an AIC of each analysis was calculated. The Zernike mode with the smallest AIC would be the most important factor in the analysis. The Zernike modes ware ranked in each analysis and compared with previous studies.
For the KC detection, the most important factor, the second, and third were vertical coma (Z3,-1)(AIC=25), defocus (Z2, 0)(AIC=51) and oblique trefoil (Z3, -3)(AIC=77). Also the most important factor for KCS was vertical coma(AIC=78), but AIC was lager than that of KC. For the KC/KCS detection, defocus(AIC=99), vertical coma(AIC=105), oblique trefoil(AIC=117) and spherical aberration(Z4,0)(AIC=117) were important factors and correspond to the degree of KC. LASIK was characterized by spherical aberration(AIC=4) and defocus(AIC=21). Pellucid has a feature of the vertical symmetry terms similar to KC, astigmatism(Z2,2)(AIC=4), vertical coma(AIC=46), and secondary astigmatism(Z4,2)(AIC=47). But for the KC/P classification, the sign of oblique trefoil(AIC=30), astigmatism(AIC=30), and spherical aberration(AIC=38) was reversed. From the result between KC and P, the oblique trefoil and astigmatism were effective to discriminate each other but vertical coma was not effective. This finding corresponds to the location of corneal thinning which was different between KC and P.
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