An assessment of intraocular pressure change in healthy subjects during air flight

Purpose: To investigate the effect of air flight on intraocular pressure (IOP). Methods: Baseline IOP of 25 healthy volunteers was measured at a ground level of 1760 feet above sea level (ASL) using Tono-Pen XL (TM). Measurements were repeated after reaching an altitude of 19,000 feet and then on the second hour during a routine flight. Cabin pressure was kept around 8000 feet. IOP measurement was repeated after landing (3.5 hr after taking off). Change in the IOP was evaluated. Results: Mean +/- SD IOP was 14.2 +/- 2.7 mmHg at ground level and was 14.0 +/- 2.2 mmHg after gaining maximum altitude (P = 0.78). Mean IOP dropped to 12.3 +/- 2.5 mmHg on the second hour of flight and 12.0 +/- 1.7 mmHg after landing. Decrease in IOP on the second hour (13.4%, p = 0.005) and after landing (15.7%, p = 0.001) were significant. Conclusion: IOP significantly decreased on the second hour measurements during a routine flight, and this change was sustained after landing.