Detecting Intraocular Pressure Harmonic Frequencies in Glaucoma and the Sampling Targets Needed to Identify Them With Self-Tonometry

This is the authors' abstract. We don't add key points for this paper.

Purpose: The purpose of this study was to determine the detectability and occurrence of circadian and ultradian rhythms in patient-acquired intraocular pressure (IOP) measurements with sampling targets for reliable harmonic detection. Methods: A multi-harmonic non-uniform discrete Fourier transform (NDFT), with bootstrap amplitude confidence intervals and independent Lomb–Scargle periodogram (LSP) confirmation, was applied to 286 home-tonometry monitoring blocks from 137 eyes of 69 patients with glaucoma. Integer harmonic frequencies (F) from 1 to 10 cycles per day were tested. Characterized frequency was defined when noise-threshold significance, amplitude lower 95% confidence bound >0, and phase 95% confidence interval met prespecified criteria. Detection probability was modeled by a logistic generalized additive model (GAM) accounting for total observation count, clock-hour coverage, and the longest sparse-data gap. Results: The 24-hour rhythm (F1) was characterized in 35.7% of blocks; at least one of F1, F2, F3, or F4 was characterized in 44.8% (128/286). Of these 128 blocks, 34% (43) had 2 or more harmonics simultaneously characterized and 7% (9) had 3 or more. Detected periodicities were almost exclusively integer harmonics. Non-integer LSP peaks arose in only 3.1% of blocks (9/286). Where 15 or more clock-hours contained at least 2 observations and no more than 2 consecutive clock-hours contained one or none, approximately 100 to 130 observations over 4 weeks gave a model-predicted detection probability of 75% to 85%, rising to 90% at approximately 150 observations. Conclusions: One or more characterizable 24-hour integer IOP harmonic rhythms could be detected with an appropriate self-tonometry protocol in nearly half of treated patients with glaucoma.