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Editors Selection IGR 8-4
Clinical Examination Methods: Telemetric IOP measurements
Comment by Crawford Downs on:
75299 Long-term follow-up after implantation of a telemetric intraocular pressure sensor in patients with glaucoma: a safety report, Koutsonas A; Walter P; Roessler G et al., Clinical and Experimental Ophthalmology, 2018; 46: 473-479
Koutsanas and colleagues published the first long-term follow-up trial on the safety of the ARGOS implantable telemetric IOP sensor in six patients. The ring-shaped sensor measures IOP using eight integrated capacitive pressure sensors and is implanted in the ciliary sulcus. A handheld reader unit powers the implanted sensor and takes a snapshot reading of IOP, allowing for home tonometry measurements. The device can only measure IOP at the time the reader is held up to the, which makes both frequent IOP measurement and tonometry during sleep impractical. Despite these limitations, an accurate home tonometer that takes a non-contact IOP measurement using a sensor inside the eye would be a major advance that would likely transform clinical glaucoma management.
The study represents a very significant accomplishment of implanting a true telemetric IOP sensor in human patientsThe present study is a retrospective analysis of long-term follow-up of the safety of the ARGOS I implantable IOP sensor that was implanted in one eye of six advanced POAG patients during cataract surgery. Safety was assessed through regular clinical examinations for an average of 37.5 months after implantation (range 21-50 months) during which time an average of 1273 IOP measurements were obtained from the sensor (range 223-2884). Mild to moderate pupil distortion and iris transillumination due to pigment dispersion were common to all patients, although there were no complaints of pain or discomfort. There were no instances of pupillary block, and the implanted eye's POAG progression rate was not obviously higher than the fellow eye, although the very small sample size renders comprehensive conclusions inconclusive. IOP readings were obtained at every attempt, although these IOP measurements were subject to significant drift errors and shifts. The errors were so significant that the authors 'do not wish to suggest that the (ARGOS I) sensor reliably measures real IOP' and hence the focus of the study is device safety. Technical limitations aside, the study represents a very significant accomplishment of implanting a true telemetric IOP sensor in human patients that will allow home tonometry when the technical issues with the pressure sensors can be remedied.
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