Conjunctival follicles versus papillae

What it is

The conjunctiva answers in one of two ways, and the difference between follicles and papillae is what tells the two red eyes apart:

• Follicle: a lymphocytic collection.
• Papillae: tissue swelling.

The two also differ in what fills them and in where their vessels run. The papilla is a tissue swelling under the conjunctival epithelium, divided by septa, with a blood vessel inside it and neutrophils and lymphocytes among the cells it holds. The follicle is a dome of lymphocytes and other mononuclear cells under the same conjunctival epithelium, and the conjunctival blood vessels sit at its base, not inside it.

Causes and risk

The adenovirus is the most common agent causing viral conjunctivitis, while allergic conjunctivitis is an IgE related immune reaction that can be acute or chronic.

The forms of allergic conjunctivitis:

• Small papillae with chemosis, thickened and erythematous lids, and corneal neovascularization: atopic, seasonal, and associated with rhinitis, asthma, dermatitis and hay fever.
• Large papillae on the superior palpebral conjunctiva: giant papillary conjunctivitis, an immune reaction to mucus debris on lenses in contact lens wearers.
• Large papillae, the cobblestones, on the superior palpebral conjunctiva with corneal ulcers and keratitis: vernal conjunctivitis, seasonal with warm weather, in children.