Source: EyeRounds.org. Contributor: Jordan M. Graff, M.D., University of Iowa.
The conjunctival vessels are the most superficial
In conjunctivitis they become diffuse and inflamed between the limbus and out towards the fornices.
Papillae
Papillae are raised areas of inflammation.
They differ in appearance from follicles by having a central blood vessel, within the raised area.
Papillae >1mm are labelled as giant papillary conjunctivitis.
Follicles
Follicles are collections of white blood cells located within the palpabral conjunctiva.
They differ from papillae by not having a central blood vessel.
They are a clinical sign of viral conjunctivitis.
Source: EyeRounds.org. Right-hand image contributor: Jordan M. Graff, M.D., University of Iowa.