Comparison between applanation tonometry and rebound tonometry in different body positions

Abstract Background To compare applanation and rebound tonometry in different body positions and assess the reliability and repeatability of clinician-measured and self-measured intraocular pressure (IOP). Methods Sixty-four glaucoma patients and glaucoma suspects underwent two consecutive IOP measurements using Goldmann applanation tonometry (GAT), iCare IC200 and self-tonometry with iCare HOME2 in seated position, and two measurements in supine position with Perkins tonometry (PAT), iCare IC200 and iCare HOME2. Central corneal thickness (CCT), lens status and other clinical variables were recorded. Agreement, repeatability, and the influence of CCT were evaluated using Bland–Altman analysis, paired t-tests, and linear regression. Results iCare HOME2 showed excellent agreement with applanation tonometry (mean difference: −0.39 mmHg seated, − 0.33 mmHg supine; both p > 0.05). iCare IC200 consistently overestimated IOP (− 0.68 mmHg vs. GAT, − 1.94 mmHg vs. PAT; p < 0.05), with a non-significant but evident trend toward increased overestimation at higher IOP levels. All devices demonstrated high repeatability in both positions (absolute Limits of Repeatability ≤ 2.73 mmHg). A negative correlation was found between CCT and IOP difference, indicating greater overestimation by rebound tonometers, particularly iCare IC200, in thicker corneas. Conclusions Rebound tonometry, especially iCare HOME2, offers reliable and repeatable IOP measurements across body positions and may represent a practical tool for self-monitoring, including in non-standard settings. CCT and IOP levels should be considered when interpreting rebound readings.