Abstract
Purpose :
To compare intraocular pressure (IOP) measurements in patients with diagnosis of glaucoma, taken using Icare Pro (ICP), Perkins (PKN) and Schiotz (SCZ) tonometers, during a nocturnal curve in supine position.
Methods :
We performed a cross-sectional, cohort, comparative and descriptive study. Fifty eyes with diagnosis of primary or secondary glaucoma were included. We excluded eyes with penetrant keratoplasty, refractive surgery, irregular astigmatism or more than three diopters, severe ocular surface disease or recent use of contact lens. IOP measurements were taken during a nocturnal curve at 18:00, 21:00, 5:00 and 6:00 hrs. All measurements were performed by the same observer, with the patient in supine position and the tonometers were calibrated prior to each measurement. In each measurement the tonometer order was as follows: ICP, PKN and SCZ, the corneal recovery interval was 5 minutes between each tonometer. The comparability of results given by the three instruments was evaluated with ANOVA, Bland-Altman method and pearson correlation.
Results :
The mean age was 62.32±16.4 years. Our principal diagnosis was primary open angle glaucoma (64%). The mean IOP was 14.96 ± 3.1 mmHg with PKN, 15.32 ± 3.08 mmHg with ICP and 13.33 ± 3.75 mmHg with SCZ, there was a statically significant difference in ANOVA test (p <0.001). The correlation between PKN and ICP was excellent (r = 0.973, p <0.001), between SCZ and PKN was poor (r=0.492, p <0.001). The agreement between ICP and PKN was good, limits of agreement were calculated to be -0.92 to +1.71 mmHg with a bias of +0.36±0.71 mmHg, PKN and SCZ tonometers showed a poor agreement with limits of -7.67 to +4.65 mmHg, bias of -1.85±4.12 mmHg.
Conclusions :
In supine position, ICP barely overestimates IOP measurements compared with the gold standard (PKN), it can be reliably used to measure IOP fluctuations during night time curves. Despite being used in multiple centers, based on our results, we discourage making clinical decisions on IOP measurements obtained with SCZ, because of its poor comparability with PKN tonometer.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.