Studies have long shown that moving in a certain way can change a patient’s intraocular pressure (IOP), albeit briefly. A new study recently documented the association, finding an immediate increase in IOP as a response to a change in body position from sitting to supine and from supine to sitting and a subsequent gradual decrease over time.

The study recruited 44 visually healthy volunteers. They were asked to begin in the sitting position (baseline) before lying down for 30 minutes and sitting back up for another 30 minutes. IOP was measured at baseline, immediately following each position change and five, 15, 25 and 30 minutes into each half-hour period.

The team found that the mean IOP increased by 2.6±2.4mmHg after lying down and by 2.1±3.1mmHg after sitting up before steadily falling. They noted that the mean IOP was 1.41±2.4mmHg higher in the lying position than it was in the sitting position, with a smaller mean difference for the lower baseline (0.9±2.2mmHg) than the higher baseline (1.9±2.5mmHg). They added that the mean IOP in the final sitting position was significantly lower (2.5±1.9mmHg) than it was in the initial sitting position.

“This effect should be considered when IOP is measured after the patient's reposition. That is, there should be an adequate timing relationship between reposition and measurement. Based on our results, the sufficient time interval must be longer than five minutes,” the study authors recommended to avoid inaccurate, misleading readings, especially as this effect is stronger for those with higher IOP—glaucoma patients.