Relationship Between Nocturnal Intraocular Pressure Variations and Sleep Macrostructure

PURPOSE. The purpose of this study was to characterize the relationships between nocturnal intraocular pressure (IOP) variations and sleep macrostructure in healthy subjects. METHODS. This was a cross-sectional study conducted in a center with shared expertise in chronobiology. Twelve healthy volunteers (22.3 +/- 2.3 years) underwent a 24-hour IOP measurement session. The IOP variations of one eye were continuously estimated using a contact lens sensor (CLS) measuring the changes in corneal curvature related to the IOP and not requiring nocturnal awakening for measurements. The CLS measurement characteristics (mean, maximum, minimum, and amplitude) were evaluated across sleep stages (non-rapid eye movement [NREM] sleep [N1, N2, N3], REM) and assessed using polysomnography. The CLS signal measurement changes during sleep stage changes were calculated to evaluate the effects of sleep on IOP. RESULTS. A 24-hour IOP nyctohemeral rhythm was found in all subjects. During the nocturnal period, IOP signal values were significantly lower during wake stages than during REM and NREM N1, N2, and N3 sleep stages (P <= 0.04). The IOP signal values were significantly higher during the REM stage than during the NREM stages (P <= 0.03) and progressively decreased as NREM sleep deepened (P <= 0.04). We found a positive relationship between the micro-arousal index and the nocturnal period CLS signal SD (r = 0.76; P = 0.024) and a negative relationship between sleep efficiency and the nocturnal period CLS signal SD (r = -0.69; P = 0.041). CONCLUSIONS. Sleep micro-and macrostructure and nocturnal IOP variations are closely related in young subjects without sleep disorders. Across sleep stages, IOP is highest during REM sleep and progressively decreases as NREM sleep deepens.