Agreement of Serial iCare HOME2 and Goldmann Applanation Tonometry

To assess agreement of iCare HOME2 and Goldmann applanation tonometry over a wide range of intraocular pressure (IOP).

A prospective, observational cohort study.

Twenty-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.

Subjects had serial iCare HOME2 (IOP_I) and Goldmann applanation (IOP_G) IOP measurements before and at 0 and 5 to 10 minutes after injection. Baseline IOPs and pachymetry were taken in both eyes.

Correlation between IOP_I and IOP_G was tested by within-subjects intraclass correlation coefficient (ICC) for repeated measures. Agreement between IOP_I and IOP_G was evaluated by a Bland-Altman plot with correction for multiple measurements. The difference between IOP_I and IOP_G was evaluated between eyes at baseline (Pearson's r) and within the injected eye over different timepoints (ICC for absolute agreement). Linear regression was used to evaluate the effects of age, sex, glaucoma, and corneal thickness.

The mean IOP_I and IOP_G were 25.3 (range: 9-55) and 23.5 (range: 8-56) mmHg, respectively. The correlation between IOP_I and IOP_G was 0.99 (P < 0.001). The mean difference (IOP_G - IOP_I) 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, 0.75-0.93), but did not show a relationship with age, sex, glaucoma, or corneal thickness.

IOP_I and IOP_G showed excellent correlation; however, there was a stable bias toward IOP_G being higher than IOP_I over a large range of IOP.

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