A pterygium is a fleshy triangular shaped accumulation of fatty or elastic tissue located on the horizontal meridian of the cornea.  As this degeneration progresses, its growth can slowly extend further onto the cornea and possibly compromise vision.  Pterygia may also cause redness, irritation, and a chronic gritty sensation.   Common causes of pterygia are chronic surface irritations such as smoking, excess friction, and exposure to UV radiation.  They are more common in environments that are windy, dirty, dusty, or closer to the equator.  Treatment may involve the use of topical steroids, decongestants, and lubrication.  Eyeglasses should contain a coating to filter out harmful UV radiation.  If the pterygium continues to grow towards the center of the cornea, or if it presents a cosmetic problem, it can be surgically removed.