Agreement of Corrected Intraocular Pressure Values Between Corvis ST and Pentacam in Patients With Keratoconus, Subclinical Keratoconus, and Normal Cornea

Purpose: To analyze the agreement of corrected intraocular pressure (IOP) values between Corvis ST (Delta IOP1) and Pentacam (Delta IOP2) in patients with keratoconus (KC), subclinical KC (sub-KC), and normal cornea. Methods: In total, 235 eyes were divided into KC, sub-KC, and control groups. Differences in Delta IOP1 (biomechanically corrected IOP minus uncorrected IOP) and Delta IOP2 (central corneal thickness-corrected amounts of IOP) were analyzed within and among groups. Topographical and biomechanical differences were compared among the 3 groups. Factors affecting differences between Delta IOP1 and Delta IOP2 were analyzed. Agreement analysis of Delta IOP2 and Delta IOP1 was performed by Bland-Altman plots for all 3 groups. Results: Mean Delta IOP1 was highest in the KC group (1.23 +/- 0.84 mm Hg), followed by sub-KC and control groups (all P < 0.05). Deformation amplitude ratio at 2 mm (DA-2 mm), integrated radius, stiffness parameter at first applanation, and Corvis biomechanical index values significantly differed between sub-KC and control groups. The differences between Delta IOP1 and Delta IOP2 were affected by stiffness parameter at first applanation, after adjusting for central corneal thickness and age, in all 3 groups. The lowest agreement between Delta IOP2 and Delta IOP1 was observed in the KC group (mean difference: 1.90 mm Hg; 95% limit of agreement ranged from -0.2 to 3.9 mm Hg). Conclusions: Among the 3 groups in this study, the KC group exhibited the worst consistency between Delta IOP2 and Delta IOP1. For the sub-KC and control groups, corrected IOP values derived by Pentacam were similar to Corvis ST. Ophthalmologists should carefully consider the mechanical properties of eyes with KC during IOP management.