A pterygium is a painless, non-cancerous growth of the conjunctiva, the lining that covers the white part of the eye. The pterygium may grow on the cornea, which covers the iris, the colored part of the eye. A pterygium usually begins at the nasal side of the eye and can be different colors, including red, pink, white, yellow or gray.
Patients with pterygium often first notice the condition because of the appearance of a lesion on their eye or because of dry, itchy irritation, tearing or redness. Pterygium is initially noticed when it is confined only to the conjunctiva. At this stage of development it is called a pinguecula. As it extends to the cornea it is termed a pterygium and can eventually lead to impaired vision.
While the causes of pterygium are not entirely known, it is believed to be caused mainly by exposure to UV light. Other suspected causes include living in a dry, dusty, and windy environment. People who live near the equator or play water sports such as surfing and fishing are more likely to develop pterygium. Prolonged exposure to these conditions causes the conjunctiva to thicken and the eye to become red and irritated. Collagen in the eye begins to deteriorate, and the eye weakens.
Studies show that there may also be a genetic predisposition to pterygium, with a higher prevalence in men than in women.
Symptoms of pterygium include:
In more severe cases, the pterygium may grow over the pupil and limit vision.
Pterygium is diagnosed after a thorough medical examination of the eyes. A slit-lamp examination will allow the physician to examine the cornea, iris and lens to confirm diagnosis.
Sunglasses that block UV rays, particularly sunglasses that provide side coverage, are a good means of protection against pterygium. Wearing a hat with a brim to limit or block sunlight is also helpful. In hot, dry climates, artificial tears should be used to help lubricate the eyes.
In most mild cases of pterygium, artificial tears can be used to reduce dryness and irritation. For those patients with severe cases of pterygium and whose vision has been affected, different types of surgery are available. Surgery is the only way to definitively remove a pterygium, but it is not a perfect solution; it requires long-term follow-up, and the recurrence rate is between 30 to 40 percent.
A safe and effective technique to surgically remove a pterygium is autologous conjunctival auto-grafting. The pterygium is removed as well as the tissue covering the conjunctiva. The tissue that is removed from the sclera is replaced by tissue that has been removed from the inside of the patient's upper eyelid.
Amniotic membrane transplantation is another safe and effective procedure to remove a pterygium. Donor tissue from an inner layer of the human placenta is used to reconstruct the surface of the eye. This type of graft encourages healing and reduces swelling.
To minimize the risk of the pterygium re-occurring, even after surgery, a radiation treatment using strontium may be recommended. Strontium plaque therapy produces beta particles that penetrate the cornea and prevents the regrowth of blood vessels that occur when the pterygium returns.