Most common cause of anterior staphyloma-
Anterior staphyloma. An ectasia of psuedocornea(the scar formed from organised exudates andfibrous tissue covered with epithelium) whichresults after total sloughing of cornea, with irisplastered behind it is called anterior staphyloma. REF:Comprehensive ophthalmology,20th edition,AK Khurana,pg no.122.
High myopia
Scleritis
Corneal ulcer
Trauma
Cornea and sclera