How Can I Differentiate Viral Conjunctivitis From Bacterial Conjunctivitis?

Marilyn W. Edmunds, PhD, NP


February 09, 2006


How can I differentiate viral conjunctivitis from bacterial conjunctivitis? What are your recommendations for management of viral conjunctivitis in school children?

Cilymol Abraham, MSN, CPNP

Response from Marilyn W. Edmunds, PhD, NP

Differentiating viral and bacterial conjunctivitis is difficult yet important to do, as the determination drives decisions about treatment and school exclusion. Conjunctivitis is a common entity in young children and, while the list of potential etiologies is large, viruses, most commonly adenovirus, cause the majority of cases.[1] Viral infections spread rapidly in daycares and schools from eye to hand to eye and, for that reason, many schools have adapted rigid exclusion policies that are not evidence-based.

The American Academy of Ophthalmology (AAO), in extensive guidelines issued in 2003, provides a comprehensive review of types of conjunctivitis and the clinical presentation.[2]

Typical Clinical Signs of Conjunctivitis
Type of Conjunctivitis Clinical Signs
Seasonal allergic Bilateral. Conjunctival injection, chemosis, watery discharge, mild mucus discharge.
Vernal Bilateral. Giant papillary hypertrophy of superior tarsal conjunctiva, bulbar conjunctival injection, conjunctival scarring, watery and mucoid discharge, limbal Trantas dots, limbal "papillae," corneal epithelial erosions, corneal neovascularization and scarring, corneal vernal plaque/shield ulcer.
Atopic Bilateral. Eczematoid blepharitis; eyelid thickening, scarring; lash loss; papillary hypertrophy of superior and inferior tarsal conjunctiva; conjunctival scarring; watery or mucoid discharge; boggy edema; corneal neovascularization, ulcers, and scarring; punctate epithelial keratitis; keratoconus; subcapsular cataract.
Giant papillary Laterality associated with contact lens wear pattern. Papillary hypertrophy of superior tarsal conjunctiva, mucoid discharge. In severe cases: lid swelling, ptosis.
Superior limbic keratoconjunctivitis (SLK) Bilateral superior bulbar injection, laxity, edema, and keratinization. Superior corneal punctate epitheliopathy and filaments.
Contact lens-related SLK Injection of superior bulbar conjunctiva, epithelial thickening of limbus with neovascularization and/or extension of conjunctival epithelium onto superior cornea. Papillary hypertrophy of tarsal conjunctivitis is variable.
Floppy eyelid syndrome Upper eyelid edema; upper eyelid easily everted, sometimes by simple elevation or lifting of lid; diffuse papillary reaction of superior tarsal conjunctiva; punctate epithelial keratopathy; pannus.
Adenoviral Abrupt onset. Unilateral or bilateral. Varies in severity. Bulbar conjunctival injection, watery discharge, follicular reaction of inferior tarsal conjunctiva, chemosis.
Distinctive signs: preauricular lymphadenopathy, petechial and subconjunctival hemorrhage, corneal epithelial defect, multifocal epithelial punctate keratitis evolving to anterior stromal keratitis, membrane/pseudomembrane formation, eyelid ecchymosis.
Herpes simplex virus Unilateral. Bulbar conjunctival injection, watery discharge, mild follicular reaction of conjunctiva. May have palpable preauricular node.
Distinctive signs: vesicular rash or ulceration of eyelids, pleomorphic or dendritic epithelial keratitis of cornea or conjunctiva.
Molluscum contagiosum Typically unilateral but can be bilateral. Mild to severe follicular reaction, punctate epithelial keratitis. May have corneal pannus, especially if longstanding.
Distinctive signs: Single or multiple shiny, dome-shaped umbilicated lesion(s) of the eyelid skin or margin.
Nongonococcal Unilateral. Bulbar conjunctival injection, purulent or mucopurulent discharge.
Gonococcal Unilateral or bilateral. Marked eyelid edema, marked bulbar conjunctival injection, marked purulent discharge, preauricular lymphadenopathy.
Important sign to detect: corneal infiltrate.
Chlamydial Unilateral or bilateral.
Neonate/Infant Eyelid edema, bulbar conjunctival injection, discharge may be purulent or mucopurulent, no follicles.
Adult Bulbar conjunctival injection, follicular reaction of tarsal conjunctiva, mucoid discharge, corneal pannus, punctate epithelial keratitis, preauricular lymphadenopathy.
Distinctive sign: bulbar conjunctival follicles.
Ocular cicatricial pemphigoid Bilateral. Bulbar conjunctival injection, papillary conjunctivitis, conjunctival subepithelial fibrosis and keratinization, conjunctival scarring beginning in the fornices, punctal stenosis and keratinization, progressive conjunctival shrinkage, symblepharon, entropion, trichiasis, corneal ulcers, neovascularization, and scarring.
Sebaceous gland carcinoma Unilateral. Intense bulbar conjunctival injection, conjunctival scarring. Corneal epithelial invasion may occur.
Eyelids may exhibit a hard nodular, nonmobile mass of the tarsal plate with yellowish discoloration; may appear as a subconjunctival, multilobulated yellow mass, may resemble a chalazion.
Medication-induced Laterality based on drug use. Conjunctival injection, inferior fornix conjunctival follicles.
Distinctive signs: contact dermatitis of eyelids with erythema, scaling in some cases.

NOTE: Typical clinical signs may not be present in all cases. Distinctive signs are most useful in making a clinical diagnosis but may occur uncommonly. In all entities, laterality may vary. May be asymmetrical. Reproduced, with permission, from Matoba AY, Preferred Practice Patterns, Conjunctivitis, San Francisco. American Academy of Ophthalmology, 2003. Available at:

Classic "pink eye," or, more appropriately, acute follicular conjunctivitis caused by adenovirus, is distinguished by bilateral watery discharge and erythema, often in the presence of a viral upper respiratory infection; a palpable preauricular node commonly occurs, sometimes on the more severely affected side.[1,3] This is the most common conjunctivitis seen in school-aged children.[4]

Bacterial conjunctivitis is less common, though the true incidence is unknown. For children outside of the neonatal age group but younger than 6 years, it is most commonly caused by Haemophilus influenzae (nontypeable) and Streptococcus pneumoniae.[4] It is associated with purulent discharge and a lesser degree of erythema.

A recent study of adults in The Netherlands sought to determine those signs and symptoms that were most predictive of a bacterial etiology for conjunctivitis. The investigators determined that awakening with one or both eyes glued shut was the single strongest predictor of a bacterial infection, with an odds ratio of 2.96 (one eye) to 14.99 (both eyes). Negative predictors included itching and a prior history of conjunctivitis.[5] The exception to this rule is the less common epidemic keratoconjunctivitis (EKC), an adenoviral infection, which causes redness, swelling, and sticky discharge from the eyes that may cause the lids to stick together. EKC is accompanied by a foreign body sensation and photophobia and may lead to chronic, painful, epithelial opacities of the cornea that can cause visual impairment.[1]

Conjunctivitis caused by adenoviruses or enteroviruses is self-limiting and requires no therapy other than careful hand washing to minimize spread to others. Artificial tears, topical antihistamines, and cool compresses may provide symptomatic relief.[3] Bacterial conjunctivitis is typically treated with one of a variety of prescription ocular antibiotics. The AAO guidelines state that this infection, too, may be self-limiting and not require antibiotics, though they caution that this practice is only approved for adults.[2]

The difficulty lies in identifying the child, often younger than 5 years old, who develops bacterial conjunctivitis as a secondary complication of a primary viral infection. For this reason, many providers opt to treat all children who present with a clinical picture consistent with conjunctivitis. Treatment with topical antibiotics shortens the course of infection and may allow a child to return to school earlier. However, a recent British study of over 300 children found that treatment with chloramphenicol or placebo resulted in virtually identical clinical cure rates and argued that most children with conjunctivitis do not require treatment.[6]

A prospective study conducted in Kentucky from 1997 to 1998 found that almost 70% of H influenzae isolates collected from 250 children with suspected conjunctivitis demonstrated beta-lactamase production.[7] Additionally, a study of postcataract surgery patients treated with fluoroquinolone found resistance rates of 4% to 50%. However, these patients had been treated, on average, for 4 weeks, a period of time much longer than is typical in conjunctivitis.[8]

While there are no universal guidelines regarding school exclusion for conjunctivitis, many schools will not allow children to return to school until they have been on antibiotics for some period of time, most typically 24 hours, or their infection has cleared. The American Academy of Pediatrics states that children with viral or bacterial conjunctivitis who do not have a concomitant systemic illness should be allowed to remain in school once any indicated therapy is implemented unless the child's behavior precludes limiting their contact with other children.[9] Therefore, young children, whose play behavior inherently requires touching and sharing toys, should be excluded from school per this recommendation. For parents, the advantage of initiating ocular antibiotics is that the child may then return to school, and the unfortunate fact that the antibiotics are not affecting the viral illness, and not mitigating subsequent spread, does not always enter into the equation.

For children who present with conjunctivitis associated with significant purulent discharge, treatment is always indicated. Ocular antibiotics should be the first choice, unless there are indications during the exam of another illness requiring systemic antibiotics. From a practical perspective, young children under the age of 5 years who present with an uncertain picture that could be bacterial, whether a primary process or a secondary result of their sticking their hands in mouths, toys, and numerous other places before touching their eyes, should also be treated with ocular antibiotics. Judicious practice argues against initiating systemic antibiotics, even in the face of parental request, in this instance unless they are indicated for another reason. While instilling eye drops in a resistant toddler is difficult, the ongoing concerns of antibiotic overuse and the resultant increase in resistance makes this the best choice.