Agreement of Serial iCare HOME2 and Goldmann Applanation Tonometry

Abstract

PurposeTo assess agreement of iCare HOME2 and Goldmann applanation tonometry over a wide range of IOP. DesignA prospective, observational cohort study. SubjectsTwenty-six adult patients undergoing intravitreal injection, which temporarily raises IOP, were recruited from the Palo Alto Medical Foundation Retina Clinic between October 2022 and February 2023. MethodsSubjects had serial iCare HOME2 (IOPI) and Goldmann applanation (IOPG) IOP measurements before and at 0 and 5-10 minutes after injection. Baseline IOPs and pachymetry were taken in both eyes. Main Outcome MeasuresCorrelation between IOPI and IOPG was tested by within-subjects Intraclass Correlation Coefficient (ICC) for repeated measures. Agreement between IOPI and IOPG was evaluated by a Bland-Altman plot with correction for multiple measurements. The difference between IOPI and IOPG was evaluated between eyes at baseline (Pearson’s r) and within the injected eye over different timepoint (ICC for absolute agreement). Linear regression was used to evaluate the effect of age, sex, glaucoma, and corneal thickness. ResultsThe mean IOPI and IOPG were 25.3 (range: 9 – 55) and 23.5 (range: 8 – 56) mmHg, respectively. Correlation between IOPI and IOPG was 0.99 (p<0.001). The mean difference (IOPG - IOPI) was 2.2 mmHg (95% limits of agreement: -3.4 to 7.8 mmHg). The bias in measurements was correlated between eyes (r: 0.68, p<0.001) and in the injected eye across all timepoints (ICC: 0.86, 95% CI: 0.75 to 0.93), but did not show a relationship with age, sex, glaucoma or corneal thickness. ConclusionIOPI and IOPG showed excellent correlation, however there was a stable bias toward IOPG being higher than IOPI over a large range of IOP.