To determine the value and accuracy of 24-hour intraocular pressure (IOP) phasing using Icare ONE rebound tonometry (RTONE), in subjects with normal tension glaucoma (NTG).Methods:
Eighteen consecutive patients with treated NTG were studied, all subjects had undergone 24-hour IOP phasing during a 1-year period. Each patient had daytime (08:00 to 16:00) IOP phasing with Goldmann applanation tonometer at 2-hourly intervals; at these same time points an IOP reading was also obtained by the patient using RTONE. Self-measured IOPs were then recorded at home using RTONE between 18:00 and 06:00 (at 2-hourly intervals). The frequency with which the phasing results altered clinical management was evaluated.Results:
The mean peak IOP was significantly higher during nighttime phasing (15.78±4.8 mm Hg) compared with daytime phasing (12.83±2.7 mm Hg, P=0.0018) and clinic IOP measurements (11.8±1.6 mm Hg, P<0.0001). Following IOP phasing a change in management occurred in 10 of 18 patients (56%). In the majority of these patients, a peak IOP was identified during nighttime phasing compared with daytime phasing, this difference was significant (P=0.0090). There were strong correlations between the IOP measurements obtained with Goldmann applanation tonometer and RTONE (Spearman r values >0.60, P<0.001).Conclusions:
This study suggests that in patients with NTG with progression that is disproportionate to their clinic IOP measurements, 24-hour phasing can reveal higher IOP spikes than those identified during typical office hours. RTONE is a safe, easy to use, and accurate device for self-monitoring of IOP.