Statistical Investigations on Relationship of Intraocular Pressure with Environmental Factors

Clinical relevance: Intraocular pressure (IOP) has a significant role in glaucoma pathophysiology. There are factors that influence in the IOP value, such as central corneal thickness or the biomechanical properties of the cornea. However, other less studied factors may influence the IOP, such as environmental pollution.

Background: The increase in air pollution is related to acute respiratory pathologies. Regarding the eyes, is related to conjunctivitis or dry eye disease. The purpose was to analyse the correlation of environmental factors (atmospheric pressure, temperature, O3, NO2, PM10 and PM2.5 concentrations) with intraocular pressure in young healthy patients.

Methods: A cross-sectional study was carried out on patients treated at General Optica centres in Spain and Portugal in collaboration with the University of Valladolid. This study included healthy patients (between 18 and 40 years old). IOP measurements were taken with different air tonometers (CT-80, CT-800, NCT-200, NT-510 and NT-530) for one week and correlated with environmental factors (atmospheric pressure, temperature, O3, NO2, PM10 and PM2.5 concentrations). Correlation (Spearman’s Rho) analyses were performed between IOP and the different environmental parameters. Moreover, groupings were performed as a function of the values for healthy exposure levels recommended by the WHO. Different comparisons were performed using the Mann‒Whitney U test.

Results: Statistically significant correlations were found (p < .04) between IOP and temperature (r = 0.37), atmospheric pressure (r = 0.20), NO2 (r = 0.14), PM10 (r = 0.21), O3 (r = 0.16) and PM2.5 concentrations (r = 0.16). Regarding the IOP values of people who were exposed to unhealthy concentrations (AQI > 20) versus those who were not, higher IOP values were only found in people exposed to PM2.5.

Conclusion: Slight correlations were found between higher temperature, atmospheric pressure and concentrations of pollutant gases and increased IOP. More clinical studies are needed to understand the role that these environmental factors play in the aqueous humour flow and the value of IOP to know if and to what extent these factors may be risk of glaucoma.