Short duration intraocular pressure patterns detected by a contact lens sensor for 24-hour recording

Abstract

Purpose: To demonstrate the ability of a contact lens sensor (CLS) to record short duration intraocular pressure (IOP) patterns.

Methods: A single-center, prospective, open label study was designed to record 24-hour IOP patterns using a CLS in healthy subjects and patients with primary open angle glaucoma (POAG). Following ophthalmic examination, eligible subjects stayed at the sleep laboratory during the 24-hour IOP recording. The CLS (Triggerfish®, Sensimed AG, Switzerland) measures the circumferential changes of the cornea at the corneoscleral junction. Short duration efficacy of the CLS was defined as recording the known phenomenon of IOP increase when going from a wake (sitting) to a sleep state in the recumbent position (W/S slope, interval 1 hr before and after sleep) and to assess the ocular pulse frequency (OPF) relative to the measured heart rate. The OPF was read from CLS output by two blinded observers. The accuracy of the CLS to detect OPF had to be ≥70% for the CLS output interval (30 seconds every 5 minutes) concurrent to that of the heart rate interval (pulse over 6 consecutive minutes, 3 times during sleep). Accuracy of detecting the OPF was reached if the lower margin of the 95.25% confidence interval (CI) was ≥75%.

Results: Twenty-nine eligible participants (27 healthy subjects and 2 glaucoma patients), were included in the analysis. The mean age was 33.7±13.8 years, and 48% were female. The mean W/S slope was significantly positive (56.9±40.5; p<0.0001). Only one participant (3.4%) had a negative W/S slope. The two observers were in agreement for 84% of OPF plots from the CLS output (evaluable 44% and non-evaluable 40%, respectively). There was no agreement between observers for 16% of plots. Plots were not evaluable because patients were woken up for other measurements. The proportion of accurate OPF plots was 86.5% (45 out 52; 95.25% CI of 75%-93.2%). Given the predefined lower margin being within the CI, the CLS was accurate in detecting a short duration IOP pattern, the OPF.

Conclusions: The CLS is capable of recording short duration IOP patterns, the W/S slope and the OPF, indicating that the CLS output represents the effect of the IOP changes on the corneoscleral junction.

Keywords: 568 intraocular pressure