Peridium

Peridiums are benign (non-cancerous) growths, but they can permanently disfigure the eye. They can also cause discomfort and blurred vision.
Causes
Although ultraviolet radiation from the sun appears to be the main cause for the development and growth of peridium, dust and wind are sometimes involved as well, as is dry eye disease.

Peridium usually develops in 30-50 years, and these eye diseases are rarely seen in children.