Ambient Air Pollution and the Risk of Central Retinal Artery Occlusion.

Purpose: To investigate whether daily changes in ambient air pollution were associated with an increased risk of central retinal artery occlusion (CRAO).

Design: Retrospective population-based cohort study.

Participants: We identified patients newly diagnosed with CRAO between 2001 and 2013 in a representative database of 1 000 000 patients that were randomly selected from all registered beneficiaries of the National Health Insurance program in Taiwan. We identified air pollutant monitoring stations located near these patients' residences in different administrative areas in Taiwan to determine the recorded concentrations of particulate matter ≤2.5 μm (PM), particulate matter ≤10 μm (PM), nitrogen dioxide (NO), sulfur dioxide (SO), and ozone (O). Patients without corresponding monitoring stations were excluded.

Methods: We used a time-stratified case-crossover study design and conditional logistic regression analysis to assess associations between the risk of CRAO and the air pollutant levels in the days preceding each event.

Main Outcome Measures: Odds ratios (ORs) and 95% confidence intervals (CIs).

Results: We enrolled 96 patients with CRAO in this study. The mean age was 65.6 years (standard deviation, 12.7 years) and 67.7% of patients were male. The risk of CRAO onset was significantly increased (OR, 1.09; 95% CI, 1.01-1.17; P = 0.03) during a 5-day period following a 1 part per billion increase in NO levels. After multipollutant adjustment, the increase in risk was most prominent after 4 days (OR, 1.40; 95% CI, 1.05-1.87; P = 0.02) to 5 days (OR, 2.16; 95% CI, 1.10-4.23; P = 0.03) of elevated NO levels in diabetic patients. The risk of CRAO onset also significantly increased in patients with hypertension and in patients ≥65 years old, after 1 day of elevated SO levels (OR, 1.88; 95% CI, 1.07-3.29; P = 0.03 and OR, 1.90; 95% CI, 1.13-3.21; P = 0.02, respectively). The transient concentration of the other air pollutants, including PM, PM, and O, did not significantly affect the occurrence of CRAO in this study.

Conclusions: These results demonstrated a positive association between air pollution and CRAO onset, particularly in patients with diabetes or hypertension and those older than 65 years.