To propose a new system of keratoconus staging using a set of parameters describing the keratoconic cone.

Retrospective case series study of 101 keratoconic eyes of 58 patients was undertaken. They all had complete eye examination including corneal topography (Oculus Pentacam). K_mean, K_max, higher order aberrations (HOAs) root mean square (HOARMS) value, pachymetry at thinnest point and steepest corneal meridian were obtained from Pentacam. Apex to thinnest pachymetry distance (D) was calculated using trigonometry. Pearson correlation coefficients between K_max and HOARMS, between D on the one hand and the adjusted angle of steepest meridian, K_mean and K_max respectively on the other, were calculated.

There is a statistically significant positive correlation between K_max and HOARMS (p < 0.00001). There is a negative correlation, a “horizontalization,” of the steep meridian with D increase, although it fell short of statistical significance (p = 0.07). D and K_mean (p = 0.003), and D and K_max (p = 0.005) are significantly negatively correlated.

K_max correlates with significant changes in HOAs. D correlates with corneal astigmatic meridian change and has a divergent path to K_mean and to K_max. We propose a new keratometry, decentration, and thinnest pachymetry staging using the parameters K_max (K), distance from the corneal apex to the thinnest pachymetry point (D), and corneal thickness at its thinnest point (T) to give a better, detailed description of a keratoconic cornea which could lead to improvements in assessment of its severity and treatment outcomes.

Tu KL, Tourkmani AK, Srinivas S. Keratoconic Cone using its Keratometry, Decentration and Thickness as Staging Parameters. Int J Kerat Ect Cor Dis 2016;5(3):99-104.