A pterygium is a triangular thin transparent conjuctival fold
visible mainly on the nasal side of the palpebral fissure. Temporally
it is more rare.
Pterygiums normally progress towards the cornea.
These pterygiums are often called cataracts by patients. This
is an incorrect term. They are easily removed by surgery under
a local surgery. Pterygiums are normally asymptomatic. Surgery
is usually indicated where the pterygium has grown on to the
cornea or where recurrent inflammations of the pterygium occur.
Images

Pterygium
Triangular, thin, transparent conjunctival fold in the palpebral
fissure. Its head is yellow, avascular and pints toward the
corneal center. The body of the pterygium extends to the semilunar
fold(32-year-old man).

Cicatrical pterygium
Differential diagnosis: the margins of the cicatricial pterygium
cannot be elevated with a probe of a foreceps. This is in contrast
to true pterygium. In the cicatrical type the conjunctival folds
are irregular, thinkened and vascularized. This type does not
show a tendency to progress toward the cornea. Charactaristics:
white. adherent to the site of corneal injury, with no avascular
head. Cause: burn. chemical injury. In this case there was injury
at the limbus (65-year-old man).