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).
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.
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).
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.
Wolverhampton & Midland Counties Eye Infirmary, Royal Wolverhampton Hospitals, Wednesfield Road, Wolverhampton, UK
Disclosure: The authors declare no conflict of interest.
Reprints: Vaneeta Sood, FRCOphth, Wolverhampton & Midland Counties Eye Infirmary, Royal Wolverhampton Hospitals, Wednesfield Road, WV10 0QR, UK (e-mail: firstname.lastname@example.org).
Received May 4, 2015
Accepted March 22, 2016