Mountain climbing involves a complex array of factors that impact eye pressure. Physical exertion, atmospheric pressure and the amount of oxygen available to your body at different altitudes all play a role in determining your eye pressure, which might increase or decrease as you climb. Moreover, your genetic makeup, age and caffeine intake affect your individual results.
Definition
Eye pressure, or intraocular pressure, is a measurement of the force exerted by fluids inside your eye against the inner walls of the organ and the structures inside, including the lens, retina and optic nerve. Your eye contains two fluids: vitreous humor, the jellylike substance inside the larger chamber of your eye, and aqueous humor, a liquid that nourishes the portion of your eye in front of the iris. The amount of vitreous humor remains constant throughout your life, but your body constantly produces and drains aqueous humor. Eye pressure changes based on the amount of aqueous humor you produce, the amount that drains from your eye and the force of air pressing on your eye from the outside. Normal intraocular pressure is between 10 and 20 mm Hg. Prolonged pressure exceeding this level can cause damage to your optic nerve.
Impact of Physical Exertion
Exercise tends to decrease eye pressure temporarily. For example, in a 2009 study reported in the online journal "BMC Ophthalmology," researchers at the Aristotle University of Thessaloniki, Greece, found that both healthy people and patients with glaucoma experienced a decrease in intraocular pressure for about an hour after jogging. The researchers suspect that exercise increases the eye's ability to drain aqueous humor and thus reduces the level of fluid pressing on the inside of the eye. The physical exertion involved in mountain climbing will tend to decrease your eye pressure, but there are other factors at play.
Altitude and Eye Pressure
As you ascend a mountain, the atmosphere becomes thinner, which means the force of the air pushing against your eye decreases. This causes your eye pressure to rise because the force of fluids pushing outward from inside your eye becomes stronger in relation to the air pressing against your eye. Your body will adjust and compensate for this change, but at extremely high altitudes, oxygen deprivation comes into play and reverses the process. In a study reported in the April 2007 issue of "Investigative Ophthalmology and Visual Science" and a separate study published in the March 2010 issue of the same journal, subjects experienced a statistically significant increase in eye pressure at elevations in the 16,000-to-20,000-foot range. In the 2007 study, the subjects remained in the same location for seven days and their eye pressure dropped as their bodies adjusted to the elevation. In the 2010 study, the subjects continued to climb and their eye pressure dropped as they ascended above 20,000 feet. The researchers theorize that oxygen deprivation at these extremely high altitudes reduces the body's production of aqueous humor, thus decreasing the pressure inside the eye.
Other Factors
Eye pressure is very individual and changes throughout the day. Unlike many other physical conditions, eye pressure is not affected by diet, blood pressure or stress levels. Caffeine consumption and steroid use, however, tend to elevate intraocular pressure. Age, family history and ethnic origin are the most significant factors that contribute to sustained elevated eye pressure, which can lead to glaucoma or macular degeneration. People of African-Caribbean descent are more prone to high intraocular pressure.
References
- "Investigative Ophthalmology and Visual Science"; Intraocular Pressure During a Very High Altitude Climb; Martina M. Bosch, et al; March 2010
- Glaucoma-Eye-Info.com: What is Intraocular Pressure?
- "BMC Ophthalmology"; Aerobic Exercise and Intraocular Pressure in Normotensive and Glaucoma Patients; Konstantinos Natsis, et al; August 13. 2009
- "Investigative Ophthalmology and Visual Science"; What Happens to Intraocular Pressure at High Altitude?; John E.A. Somner, et al; April 2007
- Tree Richardson; Eye Surgeon; Ocular Hypertension
- Open Optix: ABO Study Guide
