A pterygium is a fleshy growth of abnormal conjunctival tissue on the surface of the eye. It occurs more commonly in people with a lot of UV exposure in their early years - particularly people who surf a lot or who work outdoors without sunglasses. 

It is not a cancer but it may need to be removed if it is becoming irritable or if it is interfering with the vision. As it grows onto the cornea (the clear window if the eye) it can distort the vision by causing astigmatism or eventually grow into the line of sight.

Non-surgical management

Wearing sunglasses may slow progression of a ptergium (and reduce the likelihood of other conditions occuring such as cataract and macular damage)

Lubricating eye drops are excellent for maintaining comfort when the pterygium becomes irritated

Short courses of non-steroidal anti-inflammatory drops can also be useful for symptom control but steroid containing drops are not advised because of the risk of glaucoma or cataract development. 

Surgical excision

Successful pterygium surgery involves complete removal of all of the abnormal tissue and replacement with normal conjunctiva from another part of the eye. 

The following illustration is from the Royal Australian and New Zealand College of Ophthalmologists patient handout.