Home Tonometry Diurnal Intraocular Pressure Patterns, Patient Adherence, and Measurement Reliability in a Prospective Clinical Cohort

Abstract

Purpose: Assess patient adherence, diurnal intraocular pressure patterns, and correlation with in-office tonometry of home intraocular pressure monitoring (IOP).

Patients and methods: In this prospective cohort study, 75 patients with open-angle disease (150 eyes) were recruited and loaned the iCare HOME2 tonometer (ICH2) after in-person training and instructed to take 6 measurements per day for 10 ± 4 days. Statistical analysis of adherence, diurnal IOP patterns, and correlation with in-office tonometry was conducted.

Results: Most patients had good adherence (65% of patients took ≥ 6 measurements per day, median 7.4 measurements/day). However, adherence was poor for a notable minority of patients (19% of patients took less than 2 measurements per day). Patients with low adherence reported difficulty obtaining measurements and desire for more training with the ICH2 device. ICH2 identified diurnal patterns of IOP fluctuation: IOP varied significantly over the 24-hour day (p < 0.0001), and early morning peak IOP at 3 AM decreased significantly throughout the day to minimum mean IOP at 10 PM (p < 0.0001). IOP variance was significantly greater outside of clinic hours (p < 0.0001) and 36% of patients had maximum IOP outside of clinic hours. In-office IOP measurements had significant positive correlation to the closest ICH2 measurement obtained by the patient in time for both Goldman applanation (r² = 0.35, p < 0.0001) and iCare IC100 (r² = 0.48, p < 0.0001).

Conclusion: ICH2 is clinically useable and effective for detecting out-of-office IOP spikes, diurnal IOP patterns, and IOP variation.

Keywords: glaucoma; home monitoring; intraocular pressure fluctuation; prospective.

Figure 1

Home IOP measurement patterns of patients who took at least one measurement. Number of measurements taken by each patient (A), number of measurements per eye (B) and measurements per day (D) during the study period follow bimodal distributions. Time between first and last measurement (C) follows an approximately normal distribution.

Figure 2

Distribution of patient-level mean (A), maximum (B), and minimum (C) IOP measured by home tonometry.

Figure 3

Diurnal IOP variation measured by home tonometry. ***Significantly different mean IOP (p < 0.0001) when comparing values at the hour of the diurnal early morning maximum mean IOP to the hour of the late-day minimum mean IOP. Blue dots represent mean IOP for measurements obtained in each hour of the day. Red bars represent ± one standard deviation.

Figure 4

Regression analysis of in-office IOP by all methods (A), applanation (B), iCare (C) and tonopen (D) and closest home IOP in time. Axis labels indicate method of in-office IOP measurement compared to iCare HOME2.

Figure 5

Bland-Altman analysis of in-office IOP by all methods (A), applanation (B), iCare (C), and tonopen (D) and closest home IOP in time. Axis labels indicate method of in-office IOP measurement compared to iCare HOME2.

Figure 6

Distribution of home IOP measurements obtained between 8 AM and 5 PM (office hours) compared to in-office IOP measurements obtained during the same hours. Home and in-office IOP measurements have similar median values, but home IOP measurements show more outlying high values.