A survey of pterygia prevalence was done in 1,252 male sawmill workers and controls in British Columbia, Canada, northern India, Thailand, and Taiwan. The age-adjusted prevalence rate of pterygia in the sawmill workers was 25.3% compared to 7.1% in the control groups, a statistically highly significant finding indicating that the sawmill environment is associated with a high prevalence of pterygia. In addition, the likelihood of a pterygium developing in a sawmill worker's eye was found to increase with longer duration of employment in the mill. Both Punjabi Indian sawmill workers in British Columbia and in New Delhi had a higher prevalence of pterygia than Punjabi farmers in India. Since sawmill workers work indoors it is, therefore, unlikely that ultraviolet radiation alone is the cause of pterygia formation.
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Detels et al. (1967) studied this question.
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