Pterygium

Pterygium refers to any winglike triangular membrane occurring in the neck, eyes, knees, elbows, ankles or digits.

In the eye, a pinguecula is called a pterygium if it invades the cornea.

The term comes from the Greek word pterygion meaning "wing".

Types

A pterygium grows in response to exposure to ultraviolet light. They are more common in light-skinned people living nearer the equator, particularly where outdoor activities are popular.

As the pterygium grows, it replaces the corneal epithelium, and erodes the superficial layers beneath it. These layers are Bowman's membrane, and the anterior corneal stromal lamellae. The pterygium pulls and distorts the cornea as it enlarges.

Effects

A pterygium reduces the vision in several ways:

Pterygium (conjunctiva)

Pterygium (Surfer's Eye) most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the conjunctiva. It is usually present in the palpebral fissure. It is associated with and thought to be caused by ultraviolet-light exposure (e.g., sunlight), low humidity, and dust. The predominance of pterygia on the nasal side is possibly a result of the sun's rays passing laterally through the cornea, where it undergoes refraction and becomes focused on the limbic area. Sunlight passes unobstructed from the lateral side of the eye, focusing on the medial limbus after passing through the cornea. On the contralateral (medial) side, however, the shadow of the nose medially reduces the intensity of sunlight focused on the lateral/temporal limbus.

Signs and symptoms

Symptoms of pterygium include persistent redness from smoke, inflammation, foreign body sensation, tearing, dry and itchy eyes. In advanced cases the pterygium can affect vision as it invades the cornea with the potential of obscuring the optical center of the cornea and inducing astigmatism and corneal scarring.