pterygium is known to induce with-the-rule astigmatism.
The corneal curvature along the long axis of the pterygium body is flattened.
Recurrent or secondary pterygium often has often a growing fibrovascular tissue more exuberant than the primary.
pterygium in Medicine
pterygium pte·ryg·i·um (tə-rĭj'ē-əm) n.pl.pte·ryg·i·ums or pte·ryg·i·a (-ē-ə) An abnormal mass of tissue arising from the conjunctiva of the inner corner of the eye that obstructs vision by growing over the cornea.