Assessment of corneal biomechanics, tonometry and pachymetry with the Corvis ST in myopia

To evaluate the repeatability of Corvis ST corneal biomechanical, tonometry and pachymetry measurements, and agreement of pachymetry measures with the Pentacam HR and RTVue OCT. Three consecutive measurements of the right eye of 238 myopic subjects were acquired with the Corvis ST, Pentacam HR, and RTVue OCT. Repeatability of Corvis ST was evaluated by within-subject standard deviation [S-w] and repeatability limit [r]. The agreement of central corneal thickness (CCT) measurements were compared among the three instruments using the Bland-Altman limits of agreement. Comparisons were further stratified by CCT (Cornea(thin)<= 500 mu m; Cornea(normal)=500-550 mu m; Cornea(thick)>550 mu m). S-w was below 1 mmHg in Cornea(thin), Cornea(normal), and Cornea(thick) groups for IOP and bIOP. S-w for SP-A1 were 4.880, 6.128, 7.719 mmHg/mm respectively. S-w for CBI were 0.228, 0.157, 0.076, and correspondingly S-w for TBI and SSI were 0.094 and 0.056, 0.079 and 0.053, 0.070 and 0.053. The Bland-Altman plots for CCT implied poor agreement with mean differences of 29.49 mu m between Corvis and OCT, 9.33 mu m between Pentacam and OCT, and 20.16 mu m between Corvis and Pentacam. The Corvis ST showed good repeatability with the exception of CBI in the various CCT groups. The CCT measured by Corvis ST was not interchangeable with Pentacam HR and RTVue OCT.