Follicular Reaction on Tarsal Conjunctiva: Clinical Appearance
A follicular reaction on the tarsal conjunctiva appears as small, round, pale, elevated nodules (1-2mm) with a smooth surface and avascular centers, resembling tiny rice grains or tapioca pearls arranged in rows on the palpebral conjunctiva. 1
Anatomic Distribution in Viral Conjunctivitis
- In viral conjunctivitis, follicles predominantly appear on the inferior tarsal conjunctiva, though they can involve both upper and lower tarsal surfaces 1
- In herpes simplex virus (HSV) conjunctivitis specifically, the follicular reaction is typically mild and accompanies unilateral bulbar conjunctival injection 1, 2
- The superior tarsal conjunctiva may show follicles in HSV infection, but the reaction is generally less pronounced than in adenoviral disease 3
Key Distinguishing Features from Papillae
- Follicles have avascular pale centers with blood vessels coursing around (not through) them, whereas papillae have central vascular cores 1
- Follicles are discrete, dome-shaped elevations separated by normal conjunctiva, while papillae are polygonal elevations with fibrovascular cores 1
- Follicles represent lymphoid hyperplasia with germinal centers, distinguishing them histologically from the fibrovascular proliferation seen in papillae 4
Clinical Context in HSV Conjunctivitis
In a 7-year-old child with suspected HSV conjunctivitis:
- The follicular reaction will be mild to moderate on the tarsal conjunctiva, less florid than in adenoviral infection 1, 2, 5
- 87% of HSV conjunctivitis cases are unilateral, which helps differentiate from adenoviral disease 5
- Follicles are more commonly observed on the lower lid conjunctiva in primary HSV infection, while papillary responses tend to be more severe on the upper lid 3
- The presence of follicles alone does not distinguish HSV from adenoviral conjunctivitis in the acute stage, as clinical features overlap significantly 5
Critical Examination Steps
Evert both the upper and lower eyelids to visualize the tarsal conjunctiva fully, as follicles may be present on either surface 6, 2
Look for accompanying signs that suggest HSV:
- Vesicular lesions or ulceration on the eyelid margins 1, 2
- Palpable preauricular lymphadenopathy (common in HSV) 1, 2, 5
- Watery discharge rather than purulent 1, 2
Perform fluorescein staining immediately to detect dendritic epithelial keratitis, the pathognomonic corneal finding that distinguishes HSV from simple viral conjunctivitis and mandates antiviral therapy 6, 2
Common Pitfall
Do not assume follicular conjunctivitis is benign based on appearance alone—the critical distinction is whether corneal involvement (dendritic keratitis) is present, which transforms management from observation to immediate antiviral treatment 6, 2. Early corneal lesions may be less frequent in HSV conjunctivitis than in adenoviral disease, but missing them leads to serious complications including stromal keratitis, scarring, and perforation 1, 2, 5.