Konjungtivitis Viral

01Pathophysiology

Viral conjunctivitis results from direct viral invasion of the conjunctival epithelium, most commonly by adenovirus serotypes 3, 4, 7, 8, 19, and 37. The virus gains entry through contact with infected secretions, fomites, or contaminated water, then replicates within the epithelial cells of the conjunctiva. This triggers a cell-mediated immune response involving T-lymphocytes and monocytes, which aggregate beneath the conjunctival epithelium to form the characteristic follicles seen on the tarsal conjunctiva. These follicles are the histologic hallmark that distinguishes viral from bacterial conjunctivitis.

The immune reaction produces serous (watery) exudate rather than the purulent, thick discharge seen in bacterial infection, because the inflammatory infiltrate is predominantly lymphocytic rather than neutrophilic. This explains why the discharge in viral conjunctivitis is thin, clear, and copious.

The involvement of the preauricular lymph node reflects lymphatic drainage from the conjunctiva. Viral antigens are transported to this regional node, causing reactive lymphadenopathy. This finding is a strong clinical discriminator because bacterial conjunctivitis rarely produces palpable preauricular nodes.

The disease typically begins unilaterally, and the contralateral eye becomes involved within days due to autoinoculation from hand-to-eye contact. Adenoviral conjunctivitis can also produce subepithelial corneal infiltrates (small, round, whitish opacities) that appear 1 to 3 weeks after symptom onset. These represent antigen-antibody complexes deposited in the anterior corneal stroma and can cause prolonged photophobia and blurred vision.

Two well-recognized clinical syndromes deserve attention. Pharyngoconjunctival fever (PCF), caused by adenovirus serotypes 3 and 7, presents with conjunctivitis, pharyngitis, and fever, often in children. Epidemic keratoconjunctivitis (EKC), caused by serotypes 8, 19, and 37, is more severe with prominent corneal involvement, and is highly contagious in healthcare and institutional settings.

02Classification and Clinical Manifestation

03Diagnostic Workup

Viral conjunctivitis is overwhelmingly a clinical diagnosis. The combination of watery discharge, follicular conjunctival reaction, and preauricular lymphadenopathy in the setting of a recent URI or known contact is sufficient to establish the diagnosis in most scenarios.

Fluorescein staining with slit-lamp examination should be performed when there is concern for corneal involvement. In EKC, subepithelial infiltrates appear as scattered whitish opacities. If a dendritic ulcer is identified, the diagnosis shifts to HSV keratoconjunctivitis, which fundamentally changes management (antivirals become mandatory, and corticosteroids are contraindicated without antiviral coverage).

When the clinical picture is ambiguous or in outbreak settings, an adenoviral rapid antigen test provides point-of-care confirmation within minutes. This is particularly useful in emergency departments or ophthalmology clinics to guide infection control decisions. Viral culture remains the traditional gold standard but is slow and primarily used for public health surveillance rather than bedside decision-making.

Gram stain and bacterial culture of the discharge are not routinely needed but should be obtained when the discharge appears mucopurulent, when there is no improvement after 7 to 10 days (suggesting bacterial superinfection), or in neonates and contact lens wearers where bacterial keratitis must be excluded.

04Management and Treatment

The cornerstone of management for adenoviral conjunctivitis is supportive care. There is no effective antiviral therapy against adenovirus; the disease is self-limited and resolves within 7 to 21 days. Cool compresses reduce lid edema and provide symptomatic relief. Preservative-free artificial tears help dilute the viral load on the ocular surface and reduce irritation.

Infection control is a critical and highly testable component. Adenovirus can survive on dry surfaces for weeks, and patients remain contagious for up to 14 days after symptom onset. In healthcare settings, instrument decontamination and strict contact precautions are essential to prevent nosocomial outbreaks.

Topical antibiotics should not be prescribed for viral conjunctivitis. This is a common clinical error and a frequent test point. Unnecessary antibiotic use promotes resistance, can cause allergic reactions, and delays appropriate management if herpetic etiology is missed.

When the etiology is HSV, the management changes entirely. Topical ganciclovir gel or trifluridine drops are first-line, and oral acyclovir or valacyclovir should be added for more extensive disease or immunocompromised patients. Topical corticosteroids are strictly contraindicated in HSV keratitis unless concurrent antiviral therapy is given, because steroids suppress the local immune response and can cause explosive viral replication, stromal necrosis, and corneal perforation.

For persistent subepithelial infiltrates following EKC, low-dose topical corticosteroids (such as fluorometholone or loteprednol) may be used cautiously under ophthalmologic supervision. These infiltrates are immunologic rather than infectious, so steroids address the underlying mechanism, but they carry the risk of steroid-induced glaucoma and cataract formation with prolonged use.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on viral conjunctivitis questions is by prescribing topical antibiotics for a clearly viral presentation. When the vignette describes watery discharge, follicular reaction, preauricular lymphadenopathy, and a recent cold, the answer is supportive care only. Selecting antibiotic drops is the classic wrong answer choice designed to test whether you can differentiate viral from bacterial conjunctivitis at the bedside.

The second major trap involves missing HSV keratoconjunctivitis. If the vignette mentions vesicular lesions on the eyelid, a dendritic pattern on fluorescein staining, or recurrent unilateral episodes, the diagnosis is HSV and the management must include antivirals. Answering "supportive care only" for herpetic disease is a high-penalty error. Equally dangerous is selecting topical corticosteroids alone for any red eye with corneal involvement without first ruling out HSV, as this can lead to corneal perforation.

A third common mistake is confusing follicles with papillae. Follicles (pale, dome-shaped, avascular) point toward viral or chlamydial conjunctivitis. Papillae (red, flat-topped, with a central vascular core and "cobblestone" appearance) point toward bacterial or allergic conjunctivitis. This distinction drives the differential, and test-writers exploit it frequently.

Finally, remember that preauricular lymphadenopathy is the single most reliable physical exam finding that separates viral conjunctivitis from bacterial and allergic etiologies. If the vignette includes this finding, it is almost certainly pointing you toward a viral cause. The core competency being tested across all these questions is pattern recognition: identifying the viral triad of watery discharge, follicles, and preauricular node, resisting the urge to prescribe antibiotics, and recognizing the red flags that shift the diagnosis to HSV.