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K. Mihaltz, K. Kranitz, I. Kovacs, Z. Z. Nagy; Evaluation of Wavefront Aberrations in Patients With Keratoconus Measured With a Hartmann-Shack Sensor. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3541.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the wavefront aberrations in patients with keratoconus and to describe the characteristics of higher order aberrations observed in the disease.
Wavefront measurements with a Hartmann-Shack sensor were performed on 30 right eyes of 30 patients with keratoconus and 50 right eyes of 50 control subjects over a 4.5 mm (undilatated) pupil. Control patients were selected among refractive surgery candidates and had mostly myopic refractive error (spherical equivalent: -2.36±1.72 D). From each eye Zernike polynomial data were recorded up to the sixth-order. Receiver operating characteristic (ROC) curves were used to compare the sensitivity and specificity of the different parameters. Predictors of spherical, cylindrical and coma-like Zernike coefficients were evaluated by logistic regression analysis.
The following parameters were significantly higher in the keratoconus group compared to the control group: higher-order root mean square (HORMS) (p<0.001), Z3-1 (p<0.001), Z3-3 (p<0.002), Z33 (p=0.03), Z5-5 (p=0.03) and Z42 (p=0.045). ROC curve analyses showed best predictive accuracy for vertical coma (Z3-1) and HORMS (area under the curve: 0.93 for both), followed by horizontal trefoil (Z33) and secondary astigmatism (Z42) (0.67 and 0.66). Logistic regression analysis (LRA) showed best fit to the data for the model computed from coma-like Zernike coefficients (r2: 0.48; positive predictive value: 0.96, negative predictive value: 0.86). LRA models for spherical and astigmatic aberrations showed worse fit to the data (r2: 0.23 vs. 0.02).
Eyes with keratoconus have significantly more higher-order aberrations than normal myopic control individuals, while there was no statistically significant difference in whole eye RMS values. Coma-like aberrations are the dominant aberrations observed in keratoconus over a 4.5 mm pupil. Vertical coma can effectively discriminate keratoconus from normal myopic eyes serving as a useful diagnostic tool for detection of the disease.
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