Superficial corneal vascularization is caused by-

The clinical picture of interstitial keratitis can bedivided into three stages: initial progressive stage,florid stage and stage of regression. Florid stage. In this stage eye remains acutelyinflamed. Deep vascularization of cornea, consistingof radial bundle of brush-like vessels develops. Sincethese vessels are covered by hazy cornea, they lookdull reddish pink which is called 'Salmon patchappearance'. There is often a moderate degree ofsuperficial vascularization. These vessels arising fromthe terminal arches of conjunctival vessels, run a shodistance over the cornea. These vessels andconjunctiva heap at the limbus in the form of epulit.This stage lasts for about 2 months. REF:Comprehensive ophthalmology,4th edition,pg no.114.