Abstract

Purpose: Central corneal thickness, a marker of corneal hydration and metabolism, was reported to increase at high elevations. This study aimed to assess the effect of chronic high-altitude exposure on the central corneal thickness of healthy lowlanders with unoperated corneas, and determine if a relationship exists between exposure time and corneal edema formation. Materials and Methods: The PubMed, Embase, Scopus, Cochrane Library, and Airiti Library databases were searched up to 2017 January 31 for prospective cohort studies performed above 2500 m in healthy lowlanders with measurements of the central corneal thickness. Subjects with prior eye surgery, contact lens, and non-hypobaric hypoxic exposure were excluded. Results: Seven studies of 207 adults were included. The pooled effect of high-altitude exposure on the central corneal thickness for < 12 hours, 3–5 days, 6–7 days, and > 10 days was a mean difference of 13.4 (95% confidence interval: 5.1–21.6) μm with moderate heterogeneity (p < 0.05, I2 = 59%), 19.3 (95% confidence interval: 9.7–29) μm with low heterogeneity (p = 0.88, I2 = 0%), 20.4 (95% confidence interval: 10.3–30.5) μm with low heterogeneity (p = 0.73, I2 = 0%), and 30.8 (95% confidence interval: 20.4–41.2) μm with low heterogeneity (p = 0.69, I2 = 0%), respectively. Baseline differences between pre-exposure and post-exposure were not statistically significant. Regression analysis revealed a significant linear relation between high-altitude exposure time and corneal edema formation that exceeded 5% after 10 days. Conclusions: High-altitude exposure induces central corneal thickening with significant linear progression over time, whereas it takes over 10 days to reach clinical significance in healthy lowlanders with unoperated corneas, and changes in central corneal thickness are reversible after descent to lower elevations.

Original languageEnglish
Pages (from-to)460-465
Number of pages6
JournalCurrent Eye Research
Volume43
Issue number4
DOIs
Publication statusPublished - Apr 3 2018

Fingerprint

Meta-Analysis
Confidence Intervals
Corneal Edema
Cornea
Libraries
Corneal Pachymetry
Contact Lenses
PubMed
Cohort Studies
Regression Analysis
Databases
Prospective Studies

Keywords

  • Altitude
  • central corneal thickness
  • corneal edema

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Central Corneal Thickness of Healthy Lowlanders at High Altitude : A Systematic Review and Meta-Analysis. / Liu, Hsin Ming; Bai, Chyi Huey; Liou, Cher Ming; Chiou, Hung Yi; Chen, Chiehfeng.

In: Current Eye Research, Vol. 43, No. 4, 03.04.2018, p. 460-465.

Research output: Contribution to journalArticle

@article{038f71f4e3384053a4ff23fc5ecebc60,
title = "Central Corneal Thickness of Healthy Lowlanders at High Altitude: A Systematic Review and Meta-Analysis",
abstract = "Purpose: Central corneal thickness, a marker of corneal hydration and metabolism, was reported to increase at high elevations. This study aimed to assess the effect of chronic high-altitude exposure on the central corneal thickness of healthy lowlanders with unoperated corneas, and determine if a relationship exists between exposure time and corneal edema formation. Materials and Methods: The PubMed, Embase, Scopus, Cochrane Library, and Airiti Library databases were searched up to 2017 January 31 for prospective cohort studies performed above 2500 m in healthy lowlanders with measurements of the central corneal thickness. Subjects with prior eye surgery, contact lens, and non-hypobaric hypoxic exposure were excluded. Results: Seven studies of 207 adults were included. The pooled effect of high-altitude exposure on the central corneal thickness for < 12 hours, 3–5 days, 6–7 days, and > 10 days was a mean difference of 13.4 (95{\%} confidence interval: 5.1–21.6) μm with moderate heterogeneity (p < 0.05, I2 = 59{\%}), 19.3 (95{\%} confidence interval: 9.7–29) μm with low heterogeneity (p = 0.88, I2 = 0{\%}), 20.4 (95{\%} confidence interval: 10.3–30.5) μm with low heterogeneity (p = 0.73, I2 = 0{\%}), and 30.8 (95{\%} confidence interval: 20.4–41.2) μm with low heterogeneity (p = 0.69, I2 = 0{\%}), respectively. Baseline differences between pre-exposure and post-exposure were not statistically significant. Regression analysis revealed a significant linear relation between high-altitude exposure time and corneal edema formation that exceeded 5{\%} after 10 days. Conclusions: High-altitude exposure induces central corneal thickening with significant linear progression over time, whereas it takes over 10 days to reach clinical significance in healthy lowlanders with unoperated corneas, and changes in central corneal thickness are reversible after descent to lower elevations.",
keywords = "Altitude, central corneal thickness, corneal edema",
author = "Liu, {Hsin Ming} and Bai, {Chyi Huey} and Liou, {Cher Ming} and Chiou, {Hung Yi} and Chiehfeng Chen",
year = "2018",
month = "4",
day = "3",
doi = "10.1080/02713683.2017.1408127",
language = "English",
volume = "43",
pages = "460--465",
journal = "Current Eye Research",
issn = "0271-3683",
publisher = "Informa Healthcare",
number = "4",

}

TY - JOUR

T1 - Central Corneal Thickness of Healthy Lowlanders at High Altitude

T2 - A Systematic Review and Meta-Analysis

AU - Liu, Hsin Ming

AU - Bai, Chyi Huey

AU - Liou, Cher Ming

AU - Chiou, Hung Yi

AU - Chen, Chiehfeng

PY - 2018/4/3

Y1 - 2018/4/3

N2 - Purpose: Central corneal thickness, a marker of corneal hydration and metabolism, was reported to increase at high elevations. This study aimed to assess the effect of chronic high-altitude exposure on the central corneal thickness of healthy lowlanders with unoperated corneas, and determine if a relationship exists between exposure time and corneal edema formation. Materials and Methods: The PubMed, Embase, Scopus, Cochrane Library, and Airiti Library databases were searched up to 2017 January 31 for prospective cohort studies performed above 2500 m in healthy lowlanders with measurements of the central corneal thickness. Subjects with prior eye surgery, contact lens, and non-hypobaric hypoxic exposure were excluded. Results: Seven studies of 207 adults were included. The pooled effect of high-altitude exposure on the central corneal thickness for < 12 hours, 3–5 days, 6–7 days, and > 10 days was a mean difference of 13.4 (95% confidence interval: 5.1–21.6) μm with moderate heterogeneity (p < 0.05, I2 = 59%), 19.3 (95% confidence interval: 9.7–29) μm with low heterogeneity (p = 0.88, I2 = 0%), 20.4 (95% confidence interval: 10.3–30.5) μm with low heterogeneity (p = 0.73, I2 = 0%), and 30.8 (95% confidence interval: 20.4–41.2) μm with low heterogeneity (p = 0.69, I2 = 0%), respectively. Baseline differences between pre-exposure and post-exposure were not statistically significant. Regression analysis revealed a significant linear relation between high-altitude exposure time and corneal edema formation that exceeded 5% after 10 days. Conclusions: High-altitude exposure induces central corneal thickening with significant linear progression over time, whereas it takes over 10 days to reach clinical significance in healthy lowlanders with unoperated corneas, and changes in central corneal thickness are reversible after descent to lower elevations.

AB - Purpose: Central corneal thickness, a marker of corneal hydration and metabolism, was reported to increase at high elevations. This study aimed to assess the effect of chronic high-altitude exposure on the central corneal thickness of healthy lowlanders with unoperated corneas, and determine if a relationship exists between exposure time and corneal edema formation. Materials and Methods: The PubMed, Embase, Scopus, Cochrane Library, and Airiti Library databases were searched up to 2017 January 31 for prospective cohort studies performed above 2500 m in healthy lowlanders with measurements of the central corneal thickness. Subjects with prior eye surgery, contact lens, and non-hypobaric hypoxic exposure were excluded. Results: Seven studies of 207 adults were included. The pooled effect of high-altitude exposure on the central corneal thickness for < 12 hours, 3–5 days, 6–7 days, and > 10 days was a mean difference of 13.4 (95% confidence interval: 5.1–21.6) μm with moderate heterogeneity (p < 0.05, I2 = 59%), 19.3 (95% confidence interval: 9.7–29) μm with low heterogeneity (p = 0.88, I2 = 0%), 20.4 (95% confidence interval: 10.3–30.5) μm with low heterogeneity (p = 0.73, I2 = 0%), and 30.8 (95% confidence interval: 20.4–41.2) μm with low heterogeneity (p = 0.69, I2 = 0%), respectively. Baseline differences between pre-exposure and post-exposure were not statistically significant. Regression analysis revealed a significant linear relation between high-altitude exposure time and corneal edema formation that exceeded 5% after 10 days. Conclusions: High-altitude exposure induces central corneal thickening with significant linear progression over time, whereas it takes over 10 days to reach clinical significance in healthy lowlanders with unoperated corneas, and changes in central corneal thickness are reversible after descent to lower elevations.

KW - Altitude

KW - central corneal thickness

KW - corneal edema

UR - http://www.scopus.com/inward/record.url?scp=85038636632&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85038636632&partnerID=8YFLogxK

U2 - 10.1080/02713683.2017.1408127

DO - 10.1080/02713683.2017.1408127

M3 - Article

AN - SCOPUS:85038636632

VL - 43

SP - 460

EP - 465

JO - Current Eye Research

JF - Current Eye Research

SN - 0271-3683

IS - 4

ER -