Research Article Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus Sherine S. Wahba, 1,2 Maged M. Roshdy, 1,2 Rania S. Elkitkat, 1,2 and Karim M. Naguib 1,2 1 Faculty of Medicine, Ain Shams University, Cairo 11566, Egypt 2 Al Watany Eye Hospitals, 211 Alhegaz Street, Alhegaz Square, Heliopolis, Cairo 11361, Egypt Correspondence should be addressed to Rania S. Elkitkat; raniaselkitkat@med.asu.edu.eg Received 9 March 2016; Revised 26 June 2016; Accepted 10 July 2016 Academic Editor: Sang Beom Han Copyright © 2016 Sherine S. Wahba et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose. To evaluate accuracy of various Keratoconus (KC) screening indices, in relation to Topographic Keratoconus (TKC) grading. Setting. Al Watany Eye Hospital, Cairo, Egypt. Methods. Data of 103 normal (group 1) and 73 KC eyes (group 2), imaged by Pentacam (branded as Allegro Oculyzer), were analysed. Group 2 was divided into 2a: 14 eyes (TKC = 1, early KC), 2b: 25 eyes (TKC = 1 to 2 or 2, moderate KC), and 2c: 34 eyes (TKC = 2 to 3 up to 4, severe KC). Participants were followed up for six years to confrm diagnosis. Area under the receiver operating characteristic curve (AUROC) was calculated for evaluated curvature, elevation, and pachymetry indices with various reference shapes at diferent diameters. Results. When comparing normal to KC eyes, ten indices had signifcantly higher AUROC. Only fve of them had signifcantly higher AUROC in early KC compared to normal corneas: Pachymetry Progression Index- (PPI-) Maximum (Max), Ambr´ osio’s Relational Tickness- (ART-) Max, PPI-Max minus PPI-Minimum (Min), central corneal thickness (CCT), and diagonal decentration of thinnest point from the apex (AUROC = 0.690, 0.690, 0.687, 0.683, and 0.674, resp.). Conclusion. Generally, ten pachymetry and elevation-based indices had signifcantly higher AUROC. Five indices had statistically signifcant high AUROC when comparing early KC to normal corneas. 1. Introduction Te hallmark characteristic of Keratoconus (KC) is the devel- opment of localized, cone-shaped ectasia accompanied by corneal thinning in the area of the cone. Tis leads to irregular astigmatism and steeper corneal curvature over the area of the cone [1]. Te early detection of these changes is usually based on Placido-based corneal topography and rotating Scheimpfug camera corneal tomography. However, there are confounding conditions that can imply topographic and tomographic corneal changes resembling KC, such as corneal scarring, hyperopic refractive surgery, contact lens-induced warpage [2], and even normal variants of topographic curva- ture patterns. Tere are several tomographic criteria for KC diagnosis. Tey can be divided into three main subgroups: curvature- based, elevation-based, and pachymetry-based. Unfortu- nately, none of them is 100% sensitive and specifc. Some authors believe that elevation maps are better than axial curvature maps for KC screening [3]. Others claim that curvature is still the most sensitive [4]. Te rotating Scheimpfug camera “Pentacam” (Oculus GmbH, Wetzlar, Germany) can generate various indices within each of the three indices subgroups. Pentacam allows for measuring local elevation points by ftting the corneal shape to a best-ft sphere (BFS) reference surface with variable diameters or to a best-ft toric ellipsoid surface (BFTE), which simulates more the corneal shape than the BFS [5]. Te guidelines difer between authorities. For instance, some prefer using BFS based on the analysis of 8 mm zone around the corneal apex, especially for refractive surgery screening [6, 7], others keep the device default at 9 mm zone, although there are some concerns about it; that is, it is more difcult to get reliable scans without wide palpebral fssure. On the contrary, BFTE has been recommended for use by other studies, as they concluded that toric ellipsoid reference Hindawi Publishing Corporation Journal of Ophthalmology Volume 2016, Article ID 6392472, 9 pages http://dx.doi.org/10.1155/2016/6392472