New insights into refraction and intraocular pressure in simulated plateau environment

Abstract

Purpose To quantify the changes in intraocular pressure (IOP) and corneal refraction immediately after exposure to low-pressure hypoxia at 4500 m. Methods The study group comprised six healthy male participants 20–26 years of age. Refractive values and intraocular pressure were measured with a portable refractometer and a handheld iCare tonometer, respectively. Measurements were taken at 11 altitudes (altitude 1: ground; altitude 2: 1000 m; altitude 3: 2000 m; altitude 4: 3000 m; altitude 5: 4000 m; altitude 6: 4500 m; altitude 7: 4500 m; 40 min adaptation; altitude 8: 3500 m; altitude 9: 2500 m; altitude 10: 1500 m; altitude 11: end of experiment). Data analysis was performed using the Kolmogorov–Smirnov (K-S) test and t-test. Results K-S test results for IOP and refraction at all altitudes showed no significant change (P > 0.05), and two-tailed t-tests of measurements at the beginning of the experiment and at 4500 m, at 4500 m after 40 min of adaptation, and at the end of the experiment showed no significant change (P > 0.05). However, as the altitude increased, the refractive values indicated a tendency of myopic drift and increase astigmatism, along with increased IOP. With decreased altitude, the initial state was restored. Conclusion Hypobaric hypoxia triggers changes in IOP and refractive values, which may result in differences in a pilot's observation of the surrounding environment and judgment of dashboard information, and, further, affect flight safety.