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Editors Selection IGR 20-4

Clinical Examination Methods: 24-hour IOP monitoring

Comment by Crawford Downs on:

86206 First-in-human continuous 24-hour measurement of intraocular pressure and ocular pulsation using a novel contact lens sensor, Wasilewicz R; Varidel T; Varidel T; Simon-Zoula S et al., British Journal of Ophthalmology, 2020; 104: 1519-1523

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IOP is incredibly dynamic, and recent evidence suggests that transient IOP fluctuations comprise 10-15% of the IOP-related mechanical energy that the eye must absorb during waking hours. IOP is a principal risk factor for glaucoma, and yet we know relatively little about which aspects of IOP dynamics drive glaucomatous pathophysiology. This gap in knowledge stems primarily from the lack of continuous IOP measurement technologies in human patients. Current commercially available contact lens sensors read in arbitrary units and cannot be calibrated to an individual's IOP, which limits their use to detecting when a patient's IOP is high or low, although they cannot discern the magnitude of the IOP change. In addition, current CLS systems read in bursts, and cannot read continuously over long periods. In the present study, Wasilewicz, Mansouri and colleagues acquired IOP and OPA values with a new the pressure measuring contact lens (PMCL) device in one eye of eight patients, wherein PMCL values at the beginning of the measurement were compared with tonometry values (Goldman applanation tonometry (GAT) and dynamic contour tonometry (DCT)) in the same eye just before PMCL placement. Furthermore, IOP and OPA values measured with PMCL on the study eye during a water drinking test (WDT) were compared with DCT values in the fellow eye. In almost 90% of eyes, the PMCL mean IOP readings were within ± 5 mmHg of the GAT and DCT values, with an average mismatch of 0.18 mmHg, and IOP elevation from WDT were detectable. While this represents substantial variance in mean IOP from gold standard tonometry, OPA with PMCL and DCT matched very well. Overall, this preliminary study shows that a new noninvasive contact lens-based IOP sensor with continuous readings once per second and bursts of 50 measurements per second every three minutes is on the horizon. Most importantly, the PMCL measures IOP in mmHg, and accurately captures transient IOP fluctuations accurately over 24-hour periods, which could represent a huge step forward in achieving accurate, continuous IOP telemetry in patients.

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