Pterygium is a benign growth of the conjunctiva (a layer over the white part of the eye) that grows into the cornea (the clear layer over the coloured part of the eye). A pterygium usually begins at the nasal side of the eye, but it can also occur on the lateral side, or both.
Patients with pterygium often first notice the condition because of a focal dry, itchy irritation, or redness. A pterygium is usually first discovered when it is confined only to the conjunctiva. At this early stage, it is called a pinguecula. Once it actually extends to the cornea it is properly termed a pterygium and can eventually lead to impaired vision. A pterygium can cause astigmatism (irregular curvature of the eye), and if left untreated, can grow into the pupil and block the visual axis.