Pterygium is sunlight related, ocular-surface lesion that obscures vision. The morbidity varies in different parts of the same country. Several surveys have shown that the countries nearer the equator have higher rate of pterygium than the other regions, the possible reason is due to the low latitude and stronger exposure to ultraviolet rays.1 The onset of pterygium is closely related to the environment,2including ultraviolet rays, sandstorm, dry climate and so on. Prolonged ultraviolet-B radiation is regarded as a risk factor for pterygium, and that could explain its prevalence is much higher in the low latitude area.