The reduction of intraocular pressure (IOP) is currently the only known effective treatment available to reduce glaucomatous progression, but measurement of IOP is usually only performed during office hours every few months. However, as much as 80% of IOP peaks occur outside of scheduled appointments and frequently occur at night,1 and may be related to disease progression.2,3 Thus, there is a clear need for telemetric IOP monitoring to assess IOP throughout the day.The purpose of the study from Schmidt et al. was to report the safety, tolerability, and functionality of a telemetric IOP sensor for up to ten years from patients enrolled in the ARGOS study. 4 The device was a first-generation ring-shaped implant with eight capacitive pressure sensors that measure IOP indirectly from mechanical deflections of the capacitor membrane, and was placed in the ciliary sulcus. IOP readings were obtained on demand with a handheld reader or on a continuous basis using a modified sleep mask and eye-patch with built in antennas. The device has since been modified and CE marked as the Eyemate system (Implandata Ophthalmic Products GmbH, Hannover, Germany). Six patients received the device placed at time of cataract surgery and long-term follow-up was available in five patients (one died 13 months after surgery due to unrelated causes). The device was well-tolerated without late onset complications. Initially after the procedure, all patients had pupillary distortion and iris pigment dispersion. Four patients developed anterior chamber inflammation that resolved shortly after surgery. However, there was no ongoing inflammation beyond the early post-operative period, and pupillary distortion was not progressive. As well, there were no instances of dislocation of the pressure sensors. Importantly, the sensors in all surviving patients were still functional after ten years.
Importantly, the sensors in all surviving patients were still functional after ten years
This study provides valuable information regarding the long-term efficacy and safety of an implantable IOP sensor. Safety and tolerability appeared to be excellent even with this first generation device. However, this study was limited by its small sample size of six patients, with the vast majority of sensor measurements coming from a single patient. The remaining four surviving patients stopped regular self-tonometry after 25-51 months due to absence of ability or motivation.
The long-term safety data provided from the pioneering ARGOS study demonstrate that implantable pressure sensors are a viable and well-tolerated method for obtaining IOP measurements outside of the office for management of glaucoma
This suggests that long-term continuous IOP measurement may require a system that minimizes patient effort instead of requiring on-demand reading of the device. Also, there is limited data presented concerning the accuracy of pressure measurements from the implant. While the authors indicate that there was good correlation between Goldmann applanation tonometry and the sensor readings, and adjustments after calibration were not needed after the first few years, details were not presented. Nevertheless, the longterm safety data provided from the pioneering ARGOS study demonstrate that implantable pressure sensors are a viable and well-tolerated method for obtaining IOP measurements outside of the office for management of glaucoma.