Dilated conjunctival vessels without exudation and cellular infiltration, which can be caused by a variety of environmental irritants, including chemical fumes, wind, ultraviolet radiation and long-term topical medication, are the most common signs of acute conjunctivitis.
Conjunctival congestion is characterised by superficial vascular congestion, evident in the fornix and decreasing towards the corneal limbus; these superficial vessels may move with the mechanical movement of the conjunctiva and the congestion temporarily disappears with topical doses of epinephrine.