Air travel involves unique atmospheric conditions that can influence various bodily functions, including eye pressure (intraocular pressure). This article examines the relationship between air travel and eye pressure, focusing on the cabin environment and its impact on eye health.
Understanding Eye Pressure
Eye pressure (IOP) refers to the fluid pressure inside the eye. This pressure is primarily maintained by a clear fluid called aqueous humor, which is continuously produced and drained within the eye’s front portion. A balanced production and drainage of this fluid ensures the eye maintains its proper shape and supports healthy vision.
Normal eye pressure typically ranges from 10 to 21 millimeters of mercury (mmHg). This range is important for preserving the optic nerve, which transmits visual information to the brain. Elevated eye pressure can lead to glaucoma, a disease that can damage the optic nerve and result in permanent vision loss.
Atmospheric Changes During Flight
Commercial aircraft cabins are pressurized to simulate an altitude lower than the actual cruising altitude. This cabin pressure is typically maintained at an equivalent of 6,000 to 8,000 feet above sea level, even when the aircraft flies much higher, often between 36,000 and 40,000 feet.
The humidity levels inside an airplane cabin are notably low, often ranging from 5% to 20% relative humidity. This dry environment results from arid air taken in at cruising altitudes and the use of “bleed air” from the engines for cabin ventilation. While the percentage of oxygen in the cabin air remains similar to sea level (around 21%), the lower cabin pressure means the partial pressure of oxygen is reduced, leading to fewer oxygen molecules per breath.
Direct Effects on Eye Pressure
For most healthy individuals, atmospheric changes during air travel result in minimal and temporary fluctuations in eye pressure. Research on healthy eyes shows varied, clinically insignificant results, with some studies indicating a slight, clinically insignificant increase and others a minor decrease or no significant change. These minor changes, typically around 1 to 2 mmHg, are usually well within the eye’s natural regulatory capacity.
The eye possesses sophisticated mechanisms to maintain stable internal pressure. These regulatory processes help the eye adapt to minor external pressure variations, ensuring that any shifts in eye pressure during a flight are generally brief and resolve quickly. For healthy individuals, air travel is not considered to pose a significant risk to eye pressure.
Considerations for Existing Eye Conditions
While flying is generally safe for healthy eyes, individuals with certain pre-existing eye conditions require specific considerations regarding eye pressure. For individuals with glaucoma, air travel is generally safe as cabin pressure does not significantly increase eye pressure. However, dry cabin air can exacerbate dry eye symptoms, which can be a concern for glaucoma patients also experiencing ocular surface disease. Those with glaucoma, particularly those with advanced circulatory issues or who fly frequently, should consult their ophthalmologist before travel.
A significant concern for air travel arises for patients who have recently undergone retinal detachment surgery involving a gas bubble in the eye. Changes in altitude can cause this gas bubble to expand, leading to a painful and potentially damaging increase in intraocular pressure, which can result in severe vision loss. Therefore, flying is strictly contraindicated until the gas bubble has fully dissipated, a process that can take anywhere from two to eight weeks depending on the type and volume of gas used.
For those who have had cataract surgery, flying is generally considered safe within a few days to a week after the procedure. The new lens implanted during cataract surgery is not typically affected by cabin pressure changes. Similarly, after laser eye surgery, such as LASIK or PRK, it is usually recommended to wait at least one week before flying. The primary concern for both cataract and laser eye surgery patients is the extremely dry cabin air, which can cause discomfort and potentially hinder the healing process.
Tips for Eye Comfort
To maintain eye comfort during air travel, several practical measures can be taken. Staying well-hydrated is important; drinking plenty of water before, during, and after the flight can help counteract the dry cabin environment. Avoiding dehydrating beverages like alcohol and caffeine can further support overall hydration.
Using lubricating eye drops, particularly preservative-free artificial tears, throughout the journey can provide relief from dryness. These drops should be kept easily accessible in carry-on luggage. For contact lens wearers, switching to glasses during the flight, especially on longer journeys, can help prevent additional dryness and irritation. Directing overhead air conditioning vents away from the face also minimizes direct airflow that can contribute to dry eyes.
Limiting prolonged screen time on personal devices or in-flight entertainment can reduce eye strain and promote more frequent blinking. Consciously blinking more often helps spread the eye’s natural tears across the surface. Wearing sunglasses can protect eyes from bright cabin lights, and an eye mask can help retain moisture during sleep. Practicing good hand hygiene and avoiding touching or rubbing the eyes also helps prevent potential irritation or infection.