Under the microscope, pterygium looks like sun-damaged tissue, and indeed if you have spent a lot of time in hot, sunny places you are more likely to develop a pterygium. However, this does not explain why sometimes young people who have never lived outside the UK develop it, and sometimes there is no obvious explanation.
Other causes include:
Genetic susceptibility
Overuse of sunbeds (not proven but suspected)
Injuries to the eye (chemicals, heat burns, other injuries)
Effects of long-term eye treatments (rarely)
