Corneal thickness distribution and its relationship with corneal topography in ametropic population

Abstract

To explore the distribution of relational corneal thickness parameters including central corneal thickness (CCT), thinnest pachymetry (TP), cornea thickness spatial profile (CTSP), percentage thickness increase (PTI), pachymetric progression index (PPI) and Ambrósio's relational thickness (ART) in the normal population, and their relationships with corneal astigmatism and curvature. A total of 1 203 eyes from 1 203 normal outpatients were enrolled in this cross-sectional study. The data information of CCT, TP, CTSP, PTI, PPI-max, PPI-min, PPI-ave, axes of PPI-max and PPI-min, ART-max and ART-ave was collected from Pentacam HR for the subsequent analysis of their distribution. Astigmatism, astigmatism axis (AA), and keratometry (K) including Km and Kmax were also collected to explore their relationships with relational thickness parameters. The mean values for CCT and TP were (547.20 ± 31.441) µm and (543.26 ± 31.271) µm, respectively. The mean values for CTSP-2, CTSP-4, CTSP-6 and CTSP-8 were (552.11 ± 31.654) µm, (580.72 ± 32.919) µm, (632.11 ± 34.738) µm and (711.80 ± 37.880) µm, respectively. PTI-2, PTI-4, PTI-6 and PTI-8 were (1.67 ± 0.471)%, (6.89 ± 0.945)%, (16.37 ± 1.996)% and (31.10 ± 3.652)%. PPI-max, PPI-min and PPI-ave were 1.222 ± 0.175, 0.733 ± 0.138 and 0.994 ± 0.123. The axes of PPI-max and PPI-min were 230.74 ± 104.862 and 159.81 ± 62.292. ART-max and ART-ave were (454.940 ± 78.506)µm and (556.140 ± 86.492)µm. CCT, TP, PPI and ART were found to have a weak but significant correlation with Kmax-front, Km-front and Km-back. PPI and ART were also found to weakly correlate with Astig-back. The converted astigmatism axis was found to correlate with the axes of PPI-max (rs = -0.125, P = 0.000) and PPI-min (rs = 0.613, P = 0.000). The front and back curvatures and the back astigmatism correlate with the distribution of corneal thickness, while the front astigmatism does not correlate with it. The front astigmatism axis tends to distribute coincidently with PPI-min axis.