Assessment of Tonometry Methods in Keratoconic Eyes Following Intracorneal Ring Segments Implantation: A Comparative Study

Purpose: To compare intraocular pressure (IOP) readings from corneas with intracorneal corneal ring segments (ICRS) using various methods, including Goldmann applanation tonometry (GAT), Tonopen, corneal-compensated IOP from the Ocular Response Analyzer (ORA), and biomechanically corrected IOP from the Corneal Visualization Scheimpflug Technology (Corvis ST). Methods: This cross-sectional observational study included participants who had undergone ICRS implantation with KeraRing at least 3 months before the study. The mean IOP recorded by different instruments was compared using analysis of variance. Agreement among the methods was assessed with Bland-Altman plots. Results: A total of 54 eyes from 27 participants were enrolled. The mean IOP measured by Tonopen was significantly lower in the center compared to the peripheral quadrants (p < 0.001). IOP measured by GAT was significantly lower than that measured by Tonopen (13.02 ± 2.31 mmHg vs. 14.50 ± 2.91 mmHg, p = 0.021). There were no significant differences between the IOP measurements provided by Tonopen, ORA, and Corvis ST. The corneal-compensated IOP from ORA and biomechanically corrected IOP from Corvis ST had the highest correlation, with a weak intraclass correlation coefficient of 0.38. Conclusions: IOP measurements using Tonopen were significantly lower in the central 5-mm zone compared to other quadrants. GAT measurements were significantly lower than those from Tonopen. Different measurement tools did not show a strong correlation. Corvis ST (biomechanically corrected IOP) tended to present lower readings at higher IOP levels in eyes with ICRS.