A pterygium is fleshy tissue that grows in a triangular shape over the cornea (the transparent part or front window of the eyeball). It may grow large enough to interfere with vision. A pterygium most commonly occurs on the inner corner of the eye, with
its apex towards the pupil, but also may appear on the outer corner.

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.

An eye doctor (ophthalmologist or optometrist) can usually diagnose pingueculae and pterygia by external observation, generally using an instrument called a slit lamp. A slit lamp is a microscope with a light source and magnifies the structures of the eye for the examiner. However, because pingueculae and pterygia can sometimes look similar to more serious eye growths, it is important for people to have them checked by an eye care professional.

The primary symptom of a pterygium is a painless area of elevated white tissue, with blood vessels on the inner or outer edge of the cornea.

When a pterygium becomes red and irritated, eye drops or ointments, which can be
spread in the eye, may be used to smooth the inflammation. Large enough pterygia
that threatens sight, grows or is unsightly, can be removed surgically.
It may occur that despite proper surgical removal the pterygium returns. That affects
particularly young people. To help prevent recurrences surface radiation or
medications are sometimes used.
Wearing UV protective sunglasses and avoiding dry and dusty conditions as well as
the use of artificial tears may also help.