Mapping Corneal Thickness Using Dual-Scheimpflug Imaging at Different Stages of Keratoconus

Purpose:To map the thickness of the entire cornea using dual-Scheimpflug imaging and to evaluate the changes in the corneal thickness over the entire cornea at different stages of keratoconus.Methods:Corneal pachymetry was performed using the Galilei dual-Scheimpflug analyzer. The thinnest (TCT), central (CCT), paracentral (PaCT), and peripheral corneal thicknesses (PeCT) were also analyzed. The study examined 150 eyes of 150 patients who had myopia or myopic astigmatism and 107 eyes of 75 patients with keratoconus. Of these 107 eyes, 48 were evaluated at stage I keratoconus, 32 at stage II, 12 at stage III, and 15 at stage IV keratoconus. The level of severity of the keratoconus was based on the Amsler-Krumeich classification.Results:There were significant decreases in the thickness values of the entire corneas at all the different stages of progression defined in the Amsler-Krumeich classification. Analysis of the receiver operating characteristic curve showed that the TCT provided a better parameter than did the CCT, PaCT, and PeCT for distinguishing between keratoconus at its different stages and myopic eyes. Although the TCT and CCT parameters provided an effective distinction of eyes with stage II, III, and IV keratoconus from normal eyes, they were not effective for discriminating eyes with stage I keratoconus from eyes with myopia. But, PaCT and PeCT parameters enabled the effective discrimination between eyes with stage IV keratoconus and those with myopia only.Conclusions:The data obtained by dual-Scheimpflug imaging for the corneal thicknesses of the entire cornea provide useful information for grading the severity of keratoconus.