This book is designed to offer clarity to the clinician. It is divided into three sections: Basics, Devices, and Applications. Chapters in the Basics section are foundational and applicable to all devices, independent of specific technology. Chapter 1 focuses on corneal surface geometry, including curvature. Chapter 2 highlights the important subtleties of how elevation data are interpreted. Chapter 3 illustrates how corneal thickness maps are advantageous over single point measures of central pachymetry. Finally, Chapter 4 describes the myriad of different indices for distinguishing keratoconic from normal corneal topography that are published in the literature to date.