<prompt> In the given condition, cause of defective vision isAstigmatismHypermetropiaVisual axis is obscuredDiplopia  <response>: Pterygium: - Definition:- A degenerative condition of the subconjunctival tissue which proliferates as vascularised granulation tissue to invade the cornea . Pathogenesis:- Elastotic degeneration of the subconjunctival tissue with Fibrovascular proliferation . Destruction of epithelium Bowmans layer by advancing fibrovascular tissue resulting in corneal scarring. Cause Of Defective Vision In Pterygium:- Fibrovascular tissue contracts -- flattening of the cornea in the horizontal axis -- ASTIGMATISM WITH THE RULE ASTIGMATISM Obscuring the pupillary region or the Visual axis. Types Of Pterygium:- Depending upon the growth STOCKERS LINE:- seen in atrophic pterygium. Iron deposition in front of the head in the corneal epithelium. Ref:- Parsons Diseases of the eye 22nd edition; pg num:- 184 