Pterygium is a very common ocular abnormality. It is known as “nail” or “palm” but its technical name is pterygium. In the ocular surface is the cornea and conjunctiva. Between the cornea and conjunctiva is a fairly sharp boundary, the shape of a circle. Inside she found the cornea has no blood vessels and is transparent so you usually do not appreciate. Outside the circle is the conjunctiva that has blood vessels and we see white.
The pterygium see it as a kind of “invasion”. The conjunctiva invades the cornea, is a tip of conjunctival tissue that grows bigger from the outside of the cornea toward the center. These cells and blood vessels from the conjunctiva that are introduced, invading and placed in front of the cornea. Typically it is a kind of wedge or triangle with the apex pointing towards the pupil. Because the cornea is normally invisible seems that mounts on the iris but actually located in the cornea.