Intraocular pressure measured at ground level and 10,000 feet

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.

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.

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).

Acute change in altitude resulted in a statistically non-significant reduction in IOP in healthy subjects.