Purpose
To investigate changes in keratometric, elevation, topographic, regular and irregular astigmatism, and pachymetric parameters in keratoconus, keratoconus suspect, and normal subjects using three-dimensional (3D) corneal and anterior segment optical coherence tomography (CAS-OCT), and rotating Scheimpflug camera combined with Placido topography system (Scheimpflug camera with topography). Also, to compare discriminative ability of these parameters.
Methods
Forty eyes of 27 patients with keratoconus, 10 eyes of 10 patients with keratoconus suspect, and 77 eye of 77 normal subjects. The keratometric parameters (anterior and posterior steep K, flat K, and Average K), anterior and posterior elevation, topographic parameters, anterior and posterior regular and irregular astigmatism (spherical, asymmetry, regular, and higher order astigmatism), and pachymetric parameters (five pachymetric parameters were calculated from the region inside the 2-5 mm diameter: Minimum, Minimum-Median, Inferior-Superior, Inferotemporal Superonasal, and the vertical thinnest location of the cornea) were measured using 3D CAS-OCT and Scheimpflug camera with topography. The area under the receiver-operating curve (AROC) of keratometric, elevation, topographic, regular and irregular astigmatism, and pachymetric parameters.
Results
The keratometric parameters, anterior and posterior elevation, anterior and posterior regular and irregular astigmatism, pachymetric parameters showed good discrimination between normal and keratoconic eyes in both 3D CAS-OCT and Scheimpflug camera with topography. The AROC of all posterior parameters were higher than 0.92 and tended to be larger than anterior segment parameters. The AROC value of Inferior-Superior, posterior elevation, and posterior asymmetry were 0.940, 0.909, and 0.906 in early keratoconus discrimination analysis.
Conclusions
The keratometric parameters, anterior and posterior elevation, anterior and posterior regular and irregular astigmatism, and pachymetric parameters can effectively discriminate keratoconus. Inferior-Superior, posterior elevation, and posterior asymmetry showed best predictive accuracy in early keratoconus discrimination analysis.