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. 2024 Mar 8:15:1350051.
doi: 10.3389/fphys.2024.1350051. eCollection 2024.

High myopia at high altitudes

Ta-Wei Wang  1 , Ming-Kun Huang  2   3   4 , Chih-Chun Hsu  5 , Szu-Yang Jo  2 , Yen-Kuang Lin  6 , Chorng-Kuang How  7   8 , Shih-Fen Tseng  1 , Kong Chung  1 , Ding-Kuo Chien  2   3 , Wen-Han Chang  2   3 , Yu-Hui Chiu  2   3   9
Affiliations

High myopia at high altitudes

Ta-Wei Wang et al. Front Physiol. .

Abstract

Background: Optic nerve sheath diameter (ONSD) increases significantly at high altitudes, and is associated with the presence and severity of acute mountain sickness (AMS). Exposure to hypobaria, hypoxia, and coldness when hiking also impacts intraocular pressure (IOP). To date, little is known about ocular physiological responses in trekkers with myopia at high altitudes. This study aimed to determine changes in the ONSD and IOP between participants with and without high myopia (HM) during hiking and to test whether these changes could predict symptoms of AMS. Methods: Nine participants with HM and 18 without HM participated in a 3-day trek of Xue Mountain. The ONSD, IOP, and questionnaires were examined before and during the trek of Xue Mountain. Results: The ONSD values increased significantly in both HM (p = 0.005) and non-HM trekkers (p = 0.018) at an altitude of 1,700 m. In the HM group, IOP levels were greater than those in the non-HM group (p = 0.034) on the first day of trekking (altitude: 3,150 m). No statistically significant difference was observed between the two groups for the values of ONSD. Fractional changes in ONSD at an altitude of 1,700 m were related to the development of AMS (r pb = 0.448, p = 0.019) and the presence of headache symptoms (r pb = 0.542, p = 0.004). The area under the ROC curve for the diagnostic performance of ONSD fractional changes at an altitude of 1,700 m was 0.859 for predicting the development of AMS and 0.803 for predicting the presence of headache symptoms. Conclusion: Analysis of changes in ONSD at moderate altitude could predict AMS symptoms before an ascent to high altitude. Myopia may impact physiological accommodation at high altitudes, and HM trekkers potentially demonstrate suboptimal regulation of aqueous humor in such environments.

Keywords: acute mountain sickness; high altitudes; high myopia; intraocular pressure; optic nerve sheath diameter.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Xue Mountain hiking schedule. Echo icons mean the examining time points. Boxes present both the weather information and the examination time.
FIGURE 2
FIGURE 2
Fractional changes in ONSD and IOP at different time points. (A) shows a comparison of the fractional changes in ONSD between the two groups. (B) shows a comparison of the fractional changes in IOP between the two groups. p-value < 0.05 is considered as statistically significant. * means p-value was obtained by Mann-Whitney U test. ONSD, optic nerve sheath diameter; IOP, intraocular pressure.
FIGURE 3
FIGURE 3
ROC curve for assessing the diagnostic performance of ONSD fractional changes. (A) The ROC curve illustrates fractional changes in ONSD on day 0 at an altitude of 1,700 m and its correlation with AMS occurrence on day 2. (B) The ROC curve illustrates fractional changes in ONSD on day 0 at an altitude of 1,700 m and its correlation with headache occurrence on day 2. (C) The ROC curve illustrates fractional changes in ONSD on day 1 at an altitude of 3,150 m and its correlation with headache occurrence on day 2. ROC, receiver operating characteristic; AUC, area under the curve; ONSD, optic nerve sheath diameter; AMS, acute mountain sickness.
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