Detection of subclinical keratoconus by using corneal anterior and posterior surface aberrations and thickness spatial profiles

Abstract

PURPOSE. To assess the suitability of corneal anterior and posterior surface aberrations and thickness profile data for discrimination between eyes with early keratoconus (KC), fellow eyes of eyes with early KC, and normal eyes. METHODS. Thirty-two eyes (group 1) of 25 patients were newly diagnosed with KC; 17 eyes of 17 patients (group 2) were asymptomatic fellow eyes without clinical signs of KC. One hundred twenty-three healthy eyes of 69 patients were negative control eyes (group 3). Zernike coefficients from anterior and posterior surfaces, data from corneal thickness spatial profiles, and output values of discriminant functions based on wavefront and pachymetry data were assessed by receiver operating characteristic (ROC) curve analysis for their usefulness in discriminating between KC (groups 1, 2) eyes and control eyes. RESULTS. Vertical coma (C(3)(-1)) from the anterior surface was the coefficient with the highest ability to discriminate between groups 2 and 3 (area under the ROC curve [A(z)ROC] = 0.980; cutoff, -0.2 microm). For posterior wavefront coefficients and pachymetry data, A(z)ROC values were lower. Constructing discriminant functions from Zernike coefficients increased A(z)ROC values. The function containing first-surface data reached an A(z)ROC of 0.993; the functions containing posterior surface or pachymetry data had lower A(z)ROC values (0.932 and 0.903, respectively). The function with anterior, posterior, and pachymetry data reached an A(z)ROC of 1.0. CONCLUSIONS. Corneal wavefront and pachymetry data enabled highly accurate distinction of eyes with subclinical keratoconus from normal eyes. Posterior aberrations and thickness spatial profile data did not markedly improve discriminative ability over that of anterior wavefront data alone.