Intraocular pressure measured at ground level and 10,000 feet.

BACKGROUND: Intraocular pressure (IOP) may be subject to change during altitude exposure. This may be an important consideration for long-haul flights. In this study, intraocular pressure change was investigated following exposure to an altitude of 10,000 ft during flight in an unpressurized aircraft. METHODS: We measured the IOP of the right eye of 20 healthy volunteers (18 men, 2 women; mean age 34.6 +/- 9.5 yr) at a ground level of 1,760 ft (536 m) above the sea level (ASL) using a Tono-Pen XL tonometer. We then repeated the measurements during a flight in the unpressurized cabin of a CASA (CN235-100 M) aircraft after gaining an altitude of 10,000 ft (3,048 m) ASL. Changes in the IOP were evaluated. RESULTS: Mean IOP was 16.2 +/- 2.46 mmHg at ground level and 15.0 +/- 2.61 mmHg at 10,000 ft (3,048 m) ASL. IOP was reduced in 13 eyes, increased in 6 eyes, and remained unchanged in 1 eye. The mean change in IOP was 1.2 +/- 2.69 mmHg. However, this was not statistically significant (p = 0.06). CONCLUSION: Acute change in altitude resulted in a statistically non-significant reduction in IOP in healthy subjects.