Posture-Dependent 24-Hour Intraocular Pressure Fluctuation Patterns in an Intraocular Hypertension Monkey Model

PURPOSE: We investigate 24-hour intraocular pressure (IOP) fluctuation patterns and the influence of body position on IOP in a chronic ocular hypertension (COHT) monkey model. METHODS: We recorded 24-hour IOPs (nine time points) in the different body positions in 10 eyes with normal and eight with high IOP (with random selection of one eye of each monkey) using a Tonopen. The IOPs at various time points and in different body positions were compared. RESULTS: The average 24-hour IOPs in the immediate-supine, 10-minute supine, 10-minute seated, and immediate-seated positions in the COHT models were 28.64 ± 9.82, 25.42 ± 7.62, 23.49 ± 7.67, and 20.53 ± 7.80 mmHg, respectively. The diurnal-to-nocturnal IOP changes were 8.51 ± 2.93, 5.81 ± 3.67, 5.48 ± 2.97, and 3.59 ± 2.74 mmHg, respectively. The sudden shift between the supine and seated positions bring greater IOP variations (8.11 ± 2.85 mmHg) in the COHT monkeys, and the IOP fluctuations reached 14 to 38 mmHg when considering body position and the measurement time points. CONCLUSIONS: The measurement time and body position influenced IOP. More elevated IOP occurred in the immediate-supine position and during the transient shift between the seated and supine positions. Maintaining a fixed position for sufficient time before measurement is important. TRANSLATIONAL RELEVANCE: Glaucoma patients should focus on the importance of IOP measurements in the clinic occurring after an adequate amount of time in a fixed body position.