Alok Ranjan, B.Optom

Fellow Optometrist, Dr Shroff’s Charity Eye Hospital, New Delhi, India


Glaucoma is a group of disorders that damages the optic nerve, which is essential for good visual performance. This damage is often caused by an abnormally high intraocular pressure.

To prevent glaucomatous damage, it is very important to have a regular eye examination after the age of 40 years especially for those who have a history of glaucoma in their bloodline.

This article belongs to the effect of high altitude on intraocular pressure.

Intraocular pressure swing at higher altitude has been the subject of controversy for many years.(1) In recent times, several groups’ observations about intraocular pressure have shown increased intraocular pressure, while others show decreased intraocular pressure, normal intraocular pressure and even a reduction in intraocular pressure that occurred within hours of ascent and recovered during adaptation period. The process of these changes remains unanswered.(1) The effect of altitude on intraocular pressure and its significance may be hampered by several factors.Failure to correct central corneal thickness, which increases significantly at high altitudes can artificially swing intraocular pressure.(1)The higher altitude, the exposure duration as well as physical activity appears to play crucial role in the effect of high altitude on intraocular pressure.(1)

Hypobaric hypoxia at very high altitude causes small but statically significant changes in intraocular pressure that are regulated by systemic oxygen saturation. Climbs to very high altitude seem to be safe with regard to intraocular pressure changes.(2)

Intraocular pressure changes significantly in the ascent phases (0.58mmHg/100m) and recovered (0.71mmHg/100m) during adaptation and descent phases. Intraocular pressure changes are related to hypoxia induced respiratory alkalosis and adaptation stages.(3) Filtration surgery of primary open angle glaucoma patients in one eye may be protective against intraocular pressure fluctuations associated with ascent to high altitudes. Non-operated eye shows the increased intraocular pressure in every 1000 metre is 1.73 mmHg but there is no significant changes of intraocular pressure in filtration surgery done eye.(4)

Some studies on intraocular pressure changes of healthy low landers at different altitude levels showed significant decrease in intraocular pressure at high altitude of approx. 3,000-5,000 metre above sea-level whereas increase in intraocular pressure at extreme altitude of over 5,500 metre above sea-level with duration of exposure more than 72 hours.(5)


Therefore, the reason for the observed rise in intraocular pressure may include both changes in central corneal thickness and exercise but a complete understanding of the mechanism behind these changes remains distant.



  1. Somner JE, Morris DS, Scott KM, MacCormick IJ, Aspinall P, Dhillon B. What happens to intraocular pressure at high altitude? Investigative ophthalmology & visual science. 2007 Apr 1;48(4):1622-6.
  2. Bosch MM, Barthelmes D, Merz TM, Truffer F, Knecht PB, Petrig B, Bloch KE, Hefti U, Schubiger G, Landau K. Intraocular pressure during a very high-altitude climb. Investigative ophthalmology & visual science. 2010 Mar 1;51(3):1609-13.
  3. Pavlidis M, Stupp T, Georgalas I, Georgiadou E, Moschos M, Thanos S. Intraocular pressure changes during high-altitude acclimatisation. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2006 Mar;244(3):298-304.
  4. Foulsham W, Tatham AJ. High altitude-associated changes in intraocular pressure abrogated by trabeculectomy. Journal of Glaucoma. 2017 Oct 1;26 (10):957-60.
  5. Yang Y, Xie Y, Sun Y, Cao K, Li S, Fan S, Huang L, Wu S, Wang N. Intraocular Pressure Changes of Healthy Lowlanders at Different Altitude Levels: A Systematic Review and Meta-Analysis. Frontiers in Physiology. 2019:1366.