A wedge-shaped fibrovascular lesion arising from the bulbar conjunctiva and extending to the cornea. It is caused by chronic exposure to solar ultraviolet radiation, heat, and dust. It may cause severe vision loss. Studies have linked pterygium to neoplastic proliferation and suggest that it may be a stem cell disorder. The disease is pterygium (MONDO_0005085, a Monarch Disease Ontology term). Also known as: pterygium of conjunctiva and cornea, surfer's eye.