A pterygium is fleshy tissue that grows over the cornea (the clear front window of the eye). It may remain small or may grow large enough to interfere with vision. A pterygium commonly occurs on the inner corner of the eye, but can appear on the outer corner as well. The exact cause is not well understood. Pterygium occurs more often in people who spend a great deal of time outdoors, especially in sunny climates. Long-term exposure to sunlight, especially ultraviolet (UV) rays, and chronic eye irritation from dry, dusty conditions seem to play an important causal role. A dry eye may contribute to pterygium.
When a pterygium becomes red and irritated, eyedrops or ointments may be used to help reduce the inflammation. If the pterygium is large enough to threaten sight or grows rapidly, it can be removed surgically.
Despite proper surgical removal, the pterygium may return, particularly in young people. Protecting the eyes from excessive ultraviolet light with proper sunglasses and avoiding dry, dusty conditions and use of artificial tears may also help.
Surgery is done to remove a pterygium when it causes chronic irritation, shows growth, or produces changing astigmatism.
During the surgery, the pterygium is removed from the corneal surface and the fibrous tissue over the sclera (white) of the eye that leads up to the cornea is also removed. Leaving the area bare after pterygium removal and letting it heal on its own can promote the recurrence of the pterygium, up to 80% in some studies. The younger the patient, the more pronounced the healing response, and the higher the rate of recurrence.
There are a number of methods used to reduce the chance of regrowth of the pterygium. Dr. Kim commonly uses conjunctival tissue from under the eyelid to repair the bare sclera surface. Sometimes, she uses amniotic membrane tissue for extensive pterygium removal. Amniotic membrane is a tissue that is acquired from the innermost layer of the human placenta and has been used to replace and heal damaged mucosal surfaces including ocular surface. In order to eliminate the irritation and inflammation that accompanies suture material, Dr. Kim uses well-proven tissue glue to secure the new tissue in place instead of sutures. Her recurrence rate for pterygium is less than 8%.
When a pterygium is recurrent, the above method is used with the additional application of a drug called mitomycin C at the time of the surgery. When used in dilute form, it attenuates the healing response, calms down the surface, and deters recurrence. There are rare complications associated with the use of mitomycin C, so it generally is not used for the first operation on a pterygium.
A pinguecula is a yellowish patch or bump on the white of the eye, most often on the side closest to the nose. It is not a tumor, but an alteration of normal tissue resulting in a deposit of protein and fat. Unlike a pterygium, a pinguecula does not actually grow onto the cornea. A pinguecula may also be a response to chronic eye irritation or sunlight.
No treatment is necessary unless it becomes inflamed. A pinguecula does not grow onto the cornea or threaten sight. A pinguecula may on rare occasions be surgically removed, but the postoperative scar may be as cosmetically objectionable as the pinguecula.