The Effect of Short-Term Hypobaric Hypoxic Exposure on Intraocular Pressure

Purpose: To evaluate the effect of short-term hypobaric hypoxic conditions (STHC) on intraocular pressure (IOP) in healthy subjects. Methods: The study group was comprised of 30 healthy participants (60 eyes) with a mean age of 24.8 years. IOP was measured with a Tono-Pen XL tonometer at ground level (792 m above sea level, prehypoxic) during hypobaric hypoxic exposure (equivalent to 9144 m) and at ground level again after this exposure (post-hypoxic). For each condition, the mean of 3 consecutive measurements of IOP was calculated. In each condition, central corneal thickness was also measured. Results: IOP in the hypobaric hypoxic condition (18.23 +/- 2.84 mmHg) was significantly greater than IOP in both the prehypoxic condition (16.52 +/- 2.84 mmHg) (p < 0.001) and the post-hypoxic condition (17.02 +/- 2.52 mmHg) (p < 0.01). When corrected for hypoxia-related changes in CCT, IOP under hypobaric hypoxic conditions was still greater than IOP in both the prehypoxic and post-hypoxic conditions. There was no significant difference between IOP levels in the prehypoxic and post-hypoxic conditions (p > 0.05). Conclusion: STHC caused a significant increase in IOP in healthy participants. But this significant increase in IOP cannot be solely explained by a CCT-related overestimation error due to the increase in CCT. Individuals with IOP-related disorders such as glaucoma should be cautious when facing potential exposure to hypobaric hypoxic conditions.