A recent study published in the American Journal of Ophthalmology assessed the association between multiple air pollutants and the incidence of five common vision-threatening ocular diseases.
First, a quick refresher on air pollution.
Particulate matter (PM) refers to the mixture of solid particles and liquid droplets found in the air and is categorized into:
- PM2.5: Fine inhalable particles with diameters <2.5 μm that can embed deep into the lungs and enter the bloodstream after inhalation, posing a threat to health
- Examples: Combustion particles, organic compounds, metals
- PM10: Inhalable particles with diameters <10 μm, some of which can embed in the lung and may enter the blood stream
- Examples: Dust, pollen, mold
And in the context of ocular disease?
Air pollution is a major contributor to global disease burden, and previous studies have demonstrated that exposure to various contaminants can increase the risk of certain ocular conditions, such as:
Note: Myopic eyes may also be more vulnerable to oxidative stress and inflammation caused by exposure to air pollutants due to their altered anatomy and physiology.
Next: Talk about the study.
In this prospective cohort study, investigators included 114,930 participants with refractometry at baseline using data from the UK Biobank.
- Reminder: The UK Biobank is a large-scale prospective cohort study that recruited over 500,000 participants aged 40-69 years from 22 diverse assessment centers located across the United Kingdom between 2006 and 2010.
Annual average concentrations of the following air contaminants were measured:
- Nitrogen oxides (NOX)
- Nitrogen dioxide (NO2)
- PM2.5
- PM10
And the five vision-threatening ocular diseases evaluated in the study included:
- Cataracts
- Glaucoma
- AMD
- Diabetic retinopathy (DR)
- Retinal detachment
Findings?
Investigators observed an interquartile range increase in PM10 (hazard ratio [HR]: 1.11, 95% confidence interval [CI] 1.01-1.23), and NOX (HR: 1.22, 95% confidence interval [CI] 1.01-1.23) was significantly associated with a higher risk of DR in participants with myopia.
Moreover: PM10 was linked to a 9% increase in retinal detachment (RD) incidence in the myopic population and PM2.5 was linked to an 8% increase in glaucoma incidence in the nonmyopic population.
- Interestingly: High PM10 exposure was associated with a 61% higher risk of DR in the myopic group.
Anything else?
The impact of PM10 on DR was more pronounced in individuals with low-to-moderate myopia than those with high myopia.
Further: High PM10 exposure also correlated with a 67% higher risk of RD and a 44% higher risk of macular degeneration in the low-to-moderate myopic population.
Expert opinion?
While the underlying pathophysiology by which PM10 increases the risk of ocular diseases remains unclear, the study authors hypothesized that—due to its larger particle size—it may have a more direct impact on the ocular surface.
On the link between PM10 and DR: “For DR, the pathophysiology may involve increased oxidative stress, inflammation, endothelial dysfunction, and elevated cytokines induced by hyperglycemia, which could lead to microvascular damage in the retina,” they explained.
Limitations?
These included:
- The UK Biobank cohort primarily comprises Caucasian and British individuals with a relatively low prevalence of myopia and exposure to modest air pollution levels—potentially limiting the generalizability of the findings
- Changes in air pollution during the follow-up period could not be considered due to the unavailability of post-2010 data in the UK Biobank
- Home-based exposure assessments may not cover exposure in individuals’ work environments or during their commute
- The study could not distinguish between the affected eye(s) in cases where the disease was present in both eyes, which may have affected the interpretation of associations between air pollution and ocular diseases
- Air pollutants such as carbon monoxide (CO), ozone (O3), and sulfur dioxide (SO2), which could be related to the risk of myopia and ocular diseases, were not included in the analysis
Tie it all together for me.
These findings suggest that exposure to high levels of PM10 was associated with an increased risk of DR and RD.
For the future: The results underscore the urgency for implementing intervention strategies to mitigate the visual impairment and ocular disease burden linked with exposure to air pollution.