A pterygium is a fleshy growth that invades the cornea (the clear front window of the eye). It is an abnormal process in which the conjunctiva (a membrane that covers the white of the eye) grows into the cornea.
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.
Although pterygium and pinguecula sound like mysterious, arcane diseases, they are actually quite common, usually benign eye conditions. These lesions appear as a whitish-yellowish bump or fleshy "growth" on the exposed conjunctiva.
If the bump appears only on the white part of the eye, it is called a pinguecula. If it appears to "grow" onto the cornea, forming a winglike structure, it is called a pterygium from the Greek word for wing (pterygion).
Because these lesions look like growths, people sometimes worry that they may become malignant. In actuality, the underlying process is a degenerative one and usually does not lead to anything catastrophic such as a serious loss of vision or blindness. Most pingueculae and pterygia are slow growing and rarely cause significant problems.
Although the causes of these lesions are not completely understood, prolonged exposure to ultraviolet and infrared radiation from sunlight has been implicated. Other environmental irritants, such as dust and wind, may play a role as well. People who spend considerable time in the sun are much more likely to have pingueculae or pterygia than indoor folks. Susceptible groups include individuals who work outdoors such as farmers and fishermen or those who engage in outdoor activities such as golfing and gardening.
Usually a bump appears on the eye surface without any other symptoms. Individuals may worry that a foreign body is trapped in the eye or perhaps that a cancer is growing. An examination by an ophthalmologist will allay these worries.
There is no known method of preventing a pinguecula or pterygium. However, a prudent precaution is to protect the eye from undue sun exposure by wearing protective eyewear with good ultraviolet blockage, or at least a rimmed hat. Fortunately, most cases of pinguecula or pterygium do not constitute worrisome eye disease, and surgery usually is not necessary.