To evaluate 24-h intraocular pressure (IOP) rhythm reproducibility during repeated continuous 24-h IOP monitoring with non-contact tonometry (NCT) and a contact lens sensor (CLS) in healthy subjects.Methods
Twelve young healthy subjects were housed in a sleep laboratory and underwent four 24-h sessions of IOP measurements over a 6-month period. After randomized attribution, the IOP of the first eye was continuously monitored using the CLS Sensimed TriggerFish® and the IOP of the fellow eye was measured hourly using the Pulsair Intellipu ® non-contact tonometer. A nonlinear least-squares dual harmonic regression analysis was used to model the 24-h IOP rhythm. Comparison of acrophase, bathyphase, amplitude, the midline estimating statistic of rhythm (MESOR), IOP values, IOP changes and agreement were evaluated in the two tonometry methods.Results
A significant nyctohemeral IOP rhythm was found in 31 out of 36 sessions (86%) using NCT and in all sessions (100%) using CLS. Hourly awakening during NCT IOP measurements did not significantly change the mean phases of the 24-h IOP pattern evaluated using CLS in the contralateral eye. Throughout the sessions, intraclass correlation coefficients (ICCs) of the CLS acrophase (0.6 [0–0.9]; p=0.03), CLS bathyphase (0.7 [0.1–0.9]; p=0.01), NCT amplitude (0.7 [0.1–0.9]; p=0.01) and NCT MESOR (0.9 [0.9–1]; p<0.01) were significant.Conclusion
The CLS is an accurate and reproducible method to characterize the nyctohemeral IOP rhythm in healthy subjects but does not allow to estimate the IOP value in millimeters of mercury corresponding to the relative variation of the electrical signal measured.