Galilei™ for Keratoconus Diagnosis

Abstract

Keratoectasias are a group of corneal deformations that have ectasia as the most recognized and fundamental clinical sign in topography, tomography, and pachymetry. The Galilei™ allows the recognition and diagnosis of primary keratoectasias like keratoconus, pellucid marginal degeneration, and keratoglobus, and of the postoperative acquired secondary keratoectasia that may happen after laser refractive surgery, corneal graft transplantation, or radial keratotomy. Corneal ectasia is defined as a chronic time-dependent progressive abnormal protrusion forward identified on either of its two surfaces and caused by a biomechanical failure of the tissue. Keratoconus is the best-known and more prevalent primary keratoectasia worldwide. There is no keratoconus without ectasia, but both terms are not synonyms. Other signs of keratoconus like steepening, asymmetry, and/or thinning may be presented separately or together with or without ectasia. This chapter teaches how to identify and quantify with the Galilei™ each of these signs and shows six basic types of corneas with pre-keratoconus stages without ectasia. There is a short description of corneas with asymmetry but without steepening or ectasia, corneas with steeper astigmatism but without asymmetry or ectasia, and thin corneas without steepening or ectasia. Examples of posterior keratoconus are presented, and extreme peripheral flattening is incorporated as a new sign in keratoconus. Forme-frustre keratoconus is also depicted using the CLMI.X report, which is unique in the Galilei™. In conclusion, the Galilei™ integrates the data from dual Placido topography and dual Scheimpflug tomography, facilitating the interpretation of maps by color-coding the scales for each measured parameter and recognizing the different types of corneal deformation even before ectasia happens.