The effect of high altitude on internal eye pressure, technically called intraocular pressure (IOP), has been a controversial subject of ophthalmology studies for years. The answer to whether flying changes IOP is not as simple as yes or no.
Elevated IOP, called ocular hypertension, significantly increases the chances of developing serious eye conditions that can lead to vision loss. Ocular hypertension threatens damage to the optic nerve.
Normal eye pressure is the equal and continuous production and outflow of eye fluids. Elevated IOP occurs when there is an abundance of fluids in the eye, caused by hyper-production of fluids and/or a drainage blockage. (AllAboutVision.com's report compares it to a balloon overfilling with water.)
Study on IOP at High Altitudes
The results of a 2007 study published in "Investigative Ophthalmology and Visual Science" showed that, yes, IOP changes with altitude. The researchers concluded that the change is "statistically significant," but "clinically insignificant." IOP returned to normal levels within a few days.
The study also showed that IOP fluctuated between altitudes and returned to normal levels after a few days, possibly lowering with prolonged exposure to high altitudes.
Studies on altitude's effect on IOP examine patients with no ocular disease, or history of it. Patients with eye disease characterised by ocular hypertension, such as glaucoma, should consult an ophthalmologist before flying.
Vitrectomy Patients Warning
It can take months before natural eye fluids replace the air and gas mixture injected during a vitrectomy, and air travel is considered extremely dangerous during this healing time because of pressure changes. Get ophthalmologist approval before flying.
- AllAboutVision.com: "Ocular Hypertension," By Judith Lee and Gretchyn Bailey; reviewed by Vance Thompson, MD, October 2009
- Investigative Ophthalmology and Visual Science: "What Happens to Intraocular Pressure at High Altitude?," John E. A. Somner, et. al., 2007
- Retina-Vitreous Center P.A., Robert Wood Johnson Medical School, New Brunswick, NJ: "Vitrectomy"