Medical Edge Newspaper Column

Treating a Growth on the Cornea

October 7, 2007
Dear Mayo Clinic:
What is the newest treatment for a pterygium?

Answer:
A pterygium is an overgrowth of tissue on the surface of the eye. This benign growth slowly expands across the cornea, usually from the inner corner of the eye toward the center, assuming a triangular shape (pterygion is Greek for wing). It is bumpy, reddish, fleshy and elevated. A pterygium may have no symptoms or it may cause discomfort, including irritation and the feeling that something foreign is in the eye. Pterygia (the plural for pterygium) can be cosmetically disfiguring. In advanced cases, a pterygium can bend the cornea, resulting in astigmatism. And if it covers the pupil, it can impair vision.

There are some new and advanced surgical methods for largely eliminating pterygia. But these growths — thought to be induced by the excessive ultraviolet (UV) radiation typical of sunny regions and additionally aggravated by dryness, wind and environmental irritants such as sand — can often be managed more conservatively (nonsurgically) and even prevented.

Preventive measures when outdoors include the use of sunglasses, particularly UV-blocking and wraparound types, which will reduce exposure to harmful light, the drying effect of the wind, and windborne irritants. A wide-brimmed hat is also helpful, though it can't protect against reflected light, which can be a problem in snow and on the water.

The use of sunglasses and hats may also serve to slow the growth of an existing pterygium, though it is best if they are used with other measures.

These other measures include artificial tears or over-the-counter eye drops. They work with your own tears to lubricate the eye. Virtually any brand of this product will do. If you use artificial tears more frequently than three to four times a day, be sure to use a preservative-free brand, which is less irritating to the eye's surface. Steroid drops to reduce swelling and inflammation can help get a newly diagnosed case of pterygium under control. However, they should not be used for long, as they can increase the risk of glaucoma and cataracts. Another treatment option is a plug that blocks the tear drains (puncta) to produce an abundance of natural tears.

When surgery is needed, the procedure is straightforward. The overgrown tissue is excised from the surface of the eye. But because the pterygium's root often becomes quite intermingled with the normal surface structure of the eye, removal of the pterygium is often incomplete, and it may grow back. This occurs about 30 percent of the time when surgery involves only excision.

When either of two other techniques is used in addition to the excision of the pterygium, regrowth can be reduced. One technique uses an anti-metabolite called mitomycin C to retard the growth of residual cells. It is sponged onto the affected area in a one-time application after excision. It is critical though, that exposure to the drug and its concentration be carefully controlled to avoid harming healthy tissue.

The other technique is to place a barrier at the site, in the form of an amniotic membrane transplant. The transplanted tissue stops pterygium tissue growth. In addition, the transplanted tissue, harvested from a new mother's placenta, provides healthy cells that promote healing.

Previously, such a barrier to pterygium regrowth was created by removing tissue from elsewhere on the patient's eye and sewing it into place. The procedure was complicated and time-consuming. By contrast, amniotic membrane transplant involves just the one site on the eye and the transplanted tissue is simply "glued" on. It is much faster and highly effective, with a pterygium-recurrence rate of less than 10 percent. As a result, amniotic membrane transplant is now the standard of care when surgery is indicated.

— Dharmendra Patel, M.D., Ophthalmology, Mayo Clinic, Scottsdale, Arizona