[Corneal topography. Analysis of the corneal surface]

Various diagnostic procedures have been developed for analyzing the corneal surface. Corneal topographical measurements can be performed by classic Placido disc topographers and tomographers creating three-dimensional corneal models from cross-sectional images. Using a slit scanning system or the Scheimpflug technique additional information about the anterior segment can be obtained. New systems give us a wide range of diagnostic tools. Beside the measurement of the corneal anterior and posterior surfaces and point-to-point-pachymetry they enable analysis of corneal aberrations and measurement of the whole anterior segment, including the anterior chamber and the position of implants, pupil diameter, horizontal white-to-white and the kappa angle. Densitometry, statistical programs for the evaluation of corneal pathology and assistance with intraocular lens calculation following excimer laser treatment are further options available. This article is intended to give an overview of the principles and limitations of the various diagnostic systems.