Associations Between Regional Environment and Cornea-Related Morphology of the Eye in Young Adults: A Large-Scale Multicenter Cross-Sectional Study

Abstract

Purpose: To investigate environmental factors associated with corneal morphologic changes.

Methods: A cross-sectional study was conducted, which enrolled adults of the Han ethnicity aged 18 to 44 years from 20 cities. The cornea-related morphology was measured using an ocular anterior segment analysis system. The geographic indexes of each city and meteorological indexes of daily city-level data from the past 40 years (1980-2019) were obtained. Correlation analyses at the city level and multilevel model analyses at the eye level were performed.

Results: In total, 114,067 eyes were used for analysis. In the correlation analyses at the city level, the corneal thickness was positively correlated with the mean values of precipitation (highest r [correlation coefficient]: >0.700), temperature, and relative humidity (RH), as well as the amount of annual variation in precipitation (r: 0.548 to 0.721), and negatively correlated with the mean daily difference in the temperature (DIF T), duration of sunshine, and variance in RH (r: -0.694 to 0.495). In contrast, the anterior chamber (AC) volume was negatively correlated with the mean values of precipitation, temperature, RH, and the amount of annual variation in precipitation (r: -0.672 to -0.448), and positively associated with the mean DIF T (r = 0.570) and variance in temperature (r = 0.507). In total 19,988 eyes were analyzed at the eye level. After adjusting for age, precipitation was the major explanatory factor among the environmental factors for the variability in corneal thickness and AC volume.

Conclusions: Individuals who were raised in warm and wet environments had thicker corneas and smaller AC volumes than those from cold and dry ambient environments. Our findings demonstrate the role of local environmental factors in corneal-related morphology.

Trial registration: ClinicalTrials.gov NCT03010748.

Conflict of interest statement

Disclosure: J. Ma, None; L. Zhao, None; Y. Yang, None; D. Yun, None; P. Yu-Wai-Man, None; Y. Zhu, None; C. Chen, None; J-P.O. Li, None; M. Li, None; Y. Zhang, None; T. Cui, None; X. Meng, None; L. Zhang, None; J. Zhang, None; Y. Song, None; Y. Lei, None; J. Liu, None; X. Huangfu, None; L. Jiang, None; J. Cai, None; H. Wu, None; L. Shang, None; D. Wen, None; X. Yi, None; Y. Zhang, None; X. Li, None; J. Xiao, None; R. He, None; Y. Yang, None; J. Yang, None; G.P.M. Cheng, None; J. Bai, None; X. Zhong, None; H. Guo, None; P. Yan, None; Y. Wang, None; H. Lin, None

Figures

Figure 1.

Distribution and sample size for each study site. The shade of the map background represents the sample size, and the height of the orange column represents the percentage of the sample size. Tianjin Eye Hospital (TJE, 29,223, 25.6%, Tianjin), Jinan Mingshui Eye Hospital (JNE, 24,893, 21.8%, Jinan), Xi'an No. 4 Hospital (XAH, 17,300, 15.2%, Xi'an), The 4th people's Hospital of Shenyang (SYH, 4,737, 4.2%, Shenyang), Nanjing Aier Eye Hospital (NJE, 4,582, 4.0%, Nanjing), Shanghai Aier Eye Hospital (SHE, 4,149, 3.6%, Shanghai), Nanchang Bright Eye Hospital (NCE, 3,883, 3.4%, Nanchang), Hefei Aier Eye Hospital (HFE, 3,535, 3.1%, Hefei), Xiangya Hospital of Central South University (XYH, 3,153, 2.8%, Changsha), The First Affiliated Hospital of Xinjiang Medical University (XJH, 3,045, 2.7%, Urumqi), The Second Hospital of Jilin University (JLH, 2,563, 2.3%, Changchun), Xiamen Eye Centre of Xiamen University (XME, 2,332, 2.0%, Xiamen), Beijing Huade Eye Hospital(BJE, 2,083, 1.8%, Beijing), Shanxi Eye Hospital (SXE, 2,016, 1.8%, Taiyuan), Yan'an Hospital of Kunming City (KMH, 1,488, 1.3%, Kunming), Gansu Provincial Hospital (GSH, 1,451, 1.3%, Lanzhou), Hong Kong Laser Eye Centre (HKC, 1,229, 1.1%, Hong Kong), Daping Hospital (DPH, 1,172, 1.0%, Chongqing), Hainan Eye Hospital (HNE, 1,052, 0.9%, Haikou), and Baotou Eighth Hospital (BTH, 181, 0.2%, Baotou).

Figure 2.

Flowchart of participants in the study. A total of 301,933 eyes from 162,091 subjects were included. Subjects aged 44 years and data with missing values and outliers based on Tukey's method (interquartile range) were excluded due to the subject's lack of cooperation or error during the measurement process or data collection by the equipment. A total of 114,067 right eyes were chosen for final analyses.

Figure 3.

Relationships between corneal thickness and precipitation and relative humidity. Scatter plots and maps showing the correlations between corneal thickness and the mean (A and B) and standard deviation (C and D) of precipitation and the mean (E and F) and standard deviation (G and H) of relative humidity.

Figure 4.

Relationships between corneal thickness and temperature and sunshine duration. Scatter plots and maps showing the correlations between corneal thickness and temperature (A and B), the mean (C and D) and standard deviation (E and F) of daily difference in temperature and sunshine duration (G and H).

Figure 5.

Relationships between anterior chamber volume and precipitation and relative humidity. Scatter plots and maps showing the correlations between anterior chamber volume and the mean (A and B) and standard deviation (C and D) of precipitation and the mean (E and F) and standard deviation (G and H) of relative humidity.

Figure 6.

Relationships between anterior chamber volume and temperature. Scatter plots and maps showing the correlations between anterior chamber volume and the mean (A and B) and standard deviation (C and D) of temperature and the mean (E and F) and standard deviation (G and H) of daily difference in temperature.

Figure 7.

Relationships between corneal aberrations and temperature. Scatter plots (A) and maps (B-D) showing that several corneal parameters (higher-order abbreviations of total, front and back cornea) were negatively correlated with temperature.

Figure 8.

Relationships between latitude and corneal thickness and anterior chamber volume. Scatter plots (A and C) and maps (B and D) showing that latitude was negatively correlated with corneal thickness and positively correlated with anterior chamber volume.