Corneal vascularisation is/are caused by

VASCULARIZATION OF CORNEA Normal cornea is avascular except for small capillary loops which are present in the periphery for about 1 mm. In pathological states, it can be invaded by vessels as a defence mechanism against the disease or injury. However, vascularization interferes with corneal transparency and occasionally may be a source of irritation. Clinico-etiological features : Clinically, corneal vascularization may be superficial or deep. 1. Superficial corneal vascularization: In it vessels are arranged usually in an arborising pattern, present below the epithelial layer and their continuity can be traced with the conjunctival vessels. Common causes of superficial corneal vascularization are: trachoma, phlyctenular kerato-conjunctivitis, superficial corneal ulcers and rosacea keratitis. 2. Deep vascularization: In it the vessels are generally derived from anterior ciliary aeries and lie in the corneal stroma. These vessels are usually straight, not anastomosing and their continuity cannot be traced beyond the limbus. Deep vessels may be arranged as terminal loops, brush, parasol, umbel network or interstitial arcade. Common causes of deep vascularization are: interstitial keratitis, disciform keratitis, deep corneal ulcer, chemical burns and sclerosing keratitis and grafts. Ref:- A K KHURANA; pg num:-122,124