Keratometry consists of determining the curvature of the anterior corneal surface (the most curved and flattest meridians), expressed in diopters or centimeters of radius of curvature.
This is usually done with the autorefractor used to measure axial length, but if it is not available or appropriate, manual keratometry or corneal topography can be performed. During the last century, quantitative information on the corneal surface was obtained practically exclusively by keratometry in the clinical setting.
It has proven to be useful both for the adaptation of contact lenses on normal corneas and for other applications, such as the calculation of the power of intraocular lenses. Although the presence of more modern corneal topography systems is increasingly common in consultations, the traditional keratometer is always present; and given its historical relevance, such as the important role it still plays in the clinical setting today.
is an instrument that provides the value of the radius of curvature of the anterior face of the cornea in its central area located in front of the pupil.
It was designed to determine the radii of curvature of the principal meridians in the apical zone of the cornea, but this definition is incorrect as it actually measures curvatures in the paracentral region.
For this, it assumes that the cornea is spherical, which causes inaccuracies when measuring curvatures on highly aspherical surfaces.