24-Hour Intraocular Pressure Rhythms and Measurement Frequency in Glaucoma Using an Intraocular Telemetry Sensor

An implantable IOP sensor study in glaucoma patients found that 5 evenly spaced daily measurements over 18 waking hours effectively reflect the 24-hour IOP rhythm, with peaks and troughs often occurring outside clinic hours.

The availability of an implantable IOP sensor enables patients to obtain IOP measurements over 24 hours and on demand. The current study assesses the optimal frequency of daily IOP measurements required to reflect the 24-hour IOP rhythm in glaucoma patients.

Twenty-two patients with primary open angle glaucoma (POAG) who had previously been implanted with a sulcus-based IOP sensor (Eyemate-IO, Implandata, Germany) as part of the prospective multicentric ARGOS-02 study were enrolled. The following parameters were used to characterize the 24-hour IOP rhythm: distribution of IOP measurements and timing of IOP peaks and troughs. To assess the optimal number of IOP values to predict the 24-hour rhythm, the daily count of IOP measurements and the time interval between the first and last daily measurements were used. The correlation with the detection of daily IOP variability was assessed through Student t test and a kernel-density estimate using Gaussian kernels and Earth Movers Distance.

Twenty-two patients (8 female and 14 male) with a mean age of 67.8±6.8 years were followed up over 6.6±1.7 years with a total of 80,495 IOP measurements. The percentage of peak IOP values was highest (50.6%) during the early morning hours (4-5 am), while trough measurements occurred predominantly (42.3%) during the late-night hours (between 11 pm and 12 pm). Five IOP measurements equally distributed over an 18-hour period were sufficient to characterize the 24-hour rhythm. Additional measurements did not yield any statistically significant value in the characterization of 24-hour IOP patterns.

Using an implanted telemetric sensor, the results of this study show that 5 daily IOP measurements evenly spread over 18 hours, provide sufficient information for assessment of the diurnal IOP rhythm. However, patients in practice recorded on average 4 measurements over 14 hours, highlighting the gap between the ideal recommendation and real-life adherence.