EXPLANATION WITH IMAGES
If you think the terms are confusing, look at the illustration and photos below.
Anatomy of the eye
The white part of the eyes is the sclera. Above it is a thin layer of tissue called the conjunctiva. The colored part of the eyes is called the iris. Above the iris is the cornea, an elliptical-shaped structure that together with the lens has the function of focusing the light through the pupil to the retina. As we have already said, both the pterygium and the pinguecula appear in the sclera region. Notice in the image below how the lesions tend to be different.
the difference between pinguecula and Pterygium
On the left, the pinguecula is a lesion that can arise in the temporal portion of the eye (closest to the temple), is yellowish, higher and does not invade the corneal region. On the right, we see the pterygium, a flatter, a vascularized lesion that almost always arises in the nasal portion of the eye (closest to the nose) and frequently invades the corneal region, which can affect vision.