What are the dangers of pterygium, a conjunctival degeneration? It is less harmful when the pterygium has not yet invaded the cornea, i.e., it has not yet grown into the black eye. The pterygium body (the part that grows on the surface of the white eye) becomes congested after stimulation by ultraviolet light, dust, smoke, dryness, chemicals, etc., which affects the aesthetics. Surgery is possible if the aesthetics are seriously affected. When the head of the pterygium arrives and gradually invades the cornea, the pterygium can invade the anterior elastic layer and superficial parenchyma of the cornea, causing cellular infiltration and resulting in corneal clouding near the head of the pterygium. A hypertrophied and congested pterygium can compress the local cornea and cause astigmatism, leading to double vision. Surgery is possible. When the pterygium progresses to the pupil area, the opaque pterygium tissue blocks light from the pupil area and can affect vision. At this point, the doctor usually recommends surgery. If the pterygium completely covers the pupil area, vision can be reduced to blindness. Also, because there is scarring of the cornea after pterygium surgery, a pterygium that completely covers the pupil has limited improvement in vision even after removal.