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 intrastromal corneal ring segments (ICRS) using various methods, including Goldmann applanation tonometry (GAT), Tonopen, corneal-compensated IOP (IOPcc) from ORA, and biomechanically corrected IOP (IOPb) from Corvis ST.

Methods: This cross-sectional observational study included participants who had undergone ICRS implantation with KeraRing (Mediphacos, Belo Horizonte, Brazil) at least 3 months before the study. The mean IOP recorded by different instruments was compared using ANOVA. 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 = 0.02). There were no significant differences between the IOP measurements provided by Tonopen, ORA, and Corvis ST. The IOPcc from ORA and IOPb from Corvis ST had the highest correlation, with a weak intraclass correlation coefficient (ICC) 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 (IOPb) tended to present lower readings at higher IOP levels in eyes with ICRS.