Tangential vs sagittal videokeratographs in the "early" detection of keratoconus.

Abstract

To illustrate the difference between tangential and sagittal videokeratographs in the "early" (subclinical) detection of keratoconus. The clinically normal fellow eye of a patient with unilateral keratoconus was studied with a topographer, which can display both a sagittal and a tangential map on the same page using the same color scale. The tangential map depicted a pattern more consistent with keratoconus and provided a maximum power of 51 diopters compared with the 46 diopters of the sagittal map. Tangential videokeratographs, derived from instantaneous radius of curvature algorithms, may be more useful than sagittal displays for detecting subtle corneal topographic abnormalities.