Air Pollution and the Prevalence of Keratoconus: Is There a Connection?

Purpose: Keratoconus is a progressive, asymmetrical corneal ectasia with multifactorial origin. Three identified risk factors for keratoconus include exposure to ultraviolet (UV) rays, eye rubbing, and atopy. Other factors like pollution would play a role in the physiopathology of keratoconus. In this study we investigate the effects of particles matter (PM) of 2.5 and 10 μm, but also nitrogen dioxide (NO) and the correlation with the prevalence in the scientific literature.

Method: A literature review was performed using four databases (PubMed, Research gate, Google scholar and International Journal of Keratoconus and Ectatic Corneal Diseases) according to strict selection criteria. Levels of fine particles and nitrogen dioxide were extracted from available World Health Organization (WHO) databases and correlated with prevalences from epidemiological studies.

Results: The mean pollution rate in the selected studies was 26.88 ± 25.26 μg/m for PM , 58.23 ± 60.98 μg/m for PM and 24.79 ± 12.58 μg/m for NO. Pearson correlation tests revealed a significant positive correlation between prevalence of keratoconus with particles rate of PM ( = 0.58;  < 0.001), PM ( = 0.67;  < 0.001) and NO ( = 0.64;  = 0.00016).

Conclusion: Fine particles appear to be a risk factor for keratoconus. These pollutants may act indirectly by exacerbating known risk factors such as atopy and eye rubbing. Atmospheric pollution may also have a direct effect on the cornea, by disturbing the structure of the epithelium and increasing cell apoptosis.