Corneal densitometry, based on the Scheimpflug principle, is a useful noninvasive tool for quantitative evaluation of the optical quality of the cornea. It enables us to evaluate corneal transparency in the different corneal layers and different annuli. In this article, we discuss the basis of application of corneal densitometry measurements and summarize findings in patients with keratoconus.This article is based on a selective literature review and analysis of own data.Patients with keratoconus have significant higher corneal densitometry values compared to healthy controls. Densitometry values also correlate with the extent of the disease. In the first months after corneal cross-linking (CXL), haze formation occurs and leads to a decrease in corneal transparency, thus densitometry peaks. Long-term analysis of densitometric data have shown that corneal transparency then starts to decrease after 3 to 6 months, and improves further with time. At 24 to 36 months after CXL, corneal transparency levels might achieve physiological values.Corneal transparency is reduced in patients with keratoconus. In the first months after CXL, haze formation and a reduction in corneal transparency can be observed, which subsequently improve with time.