Pterygium: Causes
The exact cause is not well understood. Long-term exposure to sunlight, especially ultraviolet (UV) rays, and chronic eye irritation from dry; dusty conditions seem to play an important role. Hence Pterygium occurs more often in people who spend a great deal of time outdoors, especially in sunny climates. A dry eye may contribute to pterygium as well.
Risk Factors
- Ultraviolet light exposure (both UV-A and UV-B) appears to be the most significant factor in the development of pterygium including living in subtropical and tropical climates. People living near the equator are often affected. Pterygium is rare in children.
- People who spend considerable time in the sun (for example, farmers, fishermen, surfers, skiers, golfers, and gardeners) are much more likely to have pterygium than people living mostly indoors.
- Engaging in occupations that require exposure to ultraviolet (UV) light and arc, for example welders.
- Other agents that may contribute to the formation of pterygia include allergens, noxious chemicals and irritants (e.g., wind, dirt, dust, air pollution).
- A genetic predisposition to the development of pterygia appears to exist in certain families.
- Some studies report a higher prevalence of pterygia in men than in women, and this may reflect different rates of exposure to UV light.
- There is a higher rate of pterygium in people living near the equator. In the United States, the incidence is less than 2%. In Florida and California, the incidence is close to 4%. By the equator, the incidence goes up to 20%.
