Effect of ambient solar ultraviolet radiation on incidence of squamous-cell carcinoma of the eye.

Background: We have investigated the geographic distribution of squamous-cell carcinoma of the eye to assess whether solar ultraviolet light is a risk factor for this disease.
Methods: We used routinely collected population-based cancer incidence data and published measurements of ambient solar ultraviolet light in our analysis.
Findings: The incidence of squamous-cell carcinoma of the eye declined by 49% of each 10 degrees increase in latitude (p < 0.0001), falling from more than 12 cases per million per year in Uganda (latitude 0.3(0)) to less than O.2 per million per year in the UK (latitude > 50(0)). Solar ultraviolet radiation decreases with increasing latitude, and the incidence of squamous-cell carcinoma of the eye decreased by 29% per unit reduction in ultraviolet exposure (p < 0.0001).
Interpretation: Our results are compatible with the hypothesis that exposure to solar ultraviolet light is an important cause of squamous-cell carcinoma of the eye.