Keratoconus cone variants
Reviewed by Magdalena Popiela

This retrospective study examined correlation between three keratoconic parameters to further understand anatomy of keratoconic cones. Kmax and pachymetry of the thinnest point were obtained from the Pentacam scans. Decentration was calculated as distance from the corneal vertex to the thinnest point on Pentacam scans, using trigonometry. This was a novel way of calculating cone decentration. Data from 101 keratoconic eyes was studied; these were split according to Krumeich criteria into stage 1 (44 corneas), stage 2 (25 corneas), stage 3 and 4 (16 corneas each). Statistically significant positive correlation was found between pachymetry and decentration (D). Pachymetry and Kmax, as well as D and Kmax were negatively correlated. This study suggests that central keratoconic cones are thinner and steeper, whereas the peripheral ones tend to be thicker at their thinnest point and less steep. Same authors previously described a new staging system for keratoconus based on keratometry – decentration – thinnest pachymetry measurements, suggesting that progressive cone decentration could represent keratoconus evolution. Cone decentration should be considered in further studies as one of the parameters determining keratoconus progression.

Interrelationships between 3 keratoconic cone parameters.
Tu KL, Tourkmani A, Srinivas S.
CORNEA
2017;36(9):1051-3.