We read with interest the article by Ruiseñor Vázquez and associates, which reported that detectable back corneal surface abnormalities do not necessarily arise before anterior changes. However, there is another opinion that we would like to express.

We believe that posterior corneal surface elevation is a sensitive index for the early diagnosis of keratoconus. Keratoconus often occurs in the central or paracentral cornea. Elevation of posterior corneal regions near the pupil has great diagnostic value. We think that elevation of the posterior corneal surface is more valuable for describing the corneal surface abnormalities of subclinical keratoconus than the back corneal surface deviation index, and that elevations of different regions of the posterior cornea have distinct clinical values. Posterior corneal elevation is better than anterior corneal elevation for discriminating subclinical keratoconus from normal corneas. Therefore, we feel that it is necessary to evaluate the diagnostic value of posterior corneal elevation in the central or paracentral cornea for keratoconus, rather than analyze the elevation of the entire posterior corneal surface. In other words, if the authors compared the sensitivity of anterior and back corneal surface elevations rather than the front corneal surface deviation index (Df) and back corneal surface deviation index (Db), they might derive conclusions that differ from those presented in this article.

In conclusion, this article showed the efficacy of posterior corneal parameters for identifying corneas with subclinical keratoconus. However, posterior corneal surface elevation is a sensitive parameter for the diagnosis of subclinical keratoconus and is superior to anterior corneal elevation.