What is the diagnostic approach and treatment for conjunctivitis?

Diagnosing Conjunctivitis

Diagnosis of conjunctivitis relies primarily on clinical history and physical examination, with laboratory testing reserved for specific high-risk scenarios including neonatal cases, severe purulent discharge, lack of treatment response, or suspected gonococcal/chlamydial infection. 1, 2

Essential History Elements

Obtain the following specific details to guide diagnosis:

• Discharge characteristics: Purulent/mucopurulent suggests bacterial; watery suggests viral or allergic 2, 3
• Timing and laterality: Abrupt unilateral onset progressing to sequential bilateral involvement suggests viral; bilateral from onset suggests allergic 3, 4
• Eyelid matting on waking: Strongly suggests bacterial conjunctivitis 2, 5
• Itching: Most consistent feature of allergic conjunctivitis 2, 3
• Duration: Acute (<4 weeks) versus chronic (>4 weeks) 2
• Exposure history: Recent contact with infected individuals, upper respiratory infection, allergen exposure, contact lens use, recent surgery or trauma 1, 2
• Systemic symptoms: Genitourinary discharge/dysuria (suggests gonococcal/chlamydial), fever, upper respiratory infection 2
• Medical history: Immunocompromised status, atopy, previous HSV eye disease, current medications 1, 2

Physical Examination Requirements

External Examination

Evaluate systematically for:

• Preauricular lymphadenopathy: Present in viral (especially adenoviral) and hypervirulent bacterial infections 1, 3
• Skin findings: Rosacea, eczema, seborrhea, vesicular rash on eyelids or nose (suggests HSV) 1, 4
• Eyelid abnormalities: Swelling, discoloration, malposition, ulceration, nodules 1
• Conjunctival reaction pattern: Follicular (viral, chlamydial) versus papillary (bacterial, allergic) 1, 3
• Distribution: Diffuse versus sectoral 1
• Discharge type: Purulent, mucopurulent, watery, or mucoid 2, 3

Slit-Lamp Biomicroscopy

Mandatory examination includes:

• Visual acuity measurement: Essential baseline for all cases 1, 2
• Eyelid margins: Inflammation, meibomian gland dysfunction, ulceration, vesicles 1
• Eyelashes: Crusting, scurf, Demodex mites, nits, lice 1
• Bulbar conjunctiva/limbus: Follicles (inferior tarsal in viral), papillae, chemosis, hemorrhages, scarring 1, 3
• Cornea with fluorescein staining: Dendritic ulcers (HSV), infiltrates, ulceration 1, 4
• Anterior chamber: Inflammatory reaction, synechiae 1

Laboratory Testing Indications

Cultures are not cost-effective for routine uncomplicated conjunctivitis. 1 However, obtain cultures and Gram staining in these specific scenarios:

• All cases of neonatal conjunctivitis (mandatory) 1, 2
• Suspected gonococcal or MRSA infection 2
• Severe or chronic purulent conjunctivitis 1
• Recurrent conjunctivitis 1
• Lack of response to initial therapy after 3-4 days 2

Viral Diagnostic Testing

Viral testing is not routinely necessary but may be useful to:

• Prevent misdiagnosis and unnecessary antibiotic use 1
• Reduce disease spread and healthcare costs 1
• Available rapid in-office immunodiagnostic tests for adenovirus: Sensitivity 88-89%, specificity 91-94% 1
• PCR testing: Available for adenovirus, HSV, COVID-19, Zika, Mpox, and other viruses when clinically suspected based on travel history, exposures, or vaccination status 1

Differential Diagnosis Framework

Viral Conjunctivitis

• Watery discharge, follicular reaction on inferior tarsal conjunctiva, preauricular lymphadenopathy 3, 4
• Often concurrent upper respiratory infection 3, 4
• Abrupt onset, initially unilateral becoming sequentially bilateral 3, 4
• May have subconjunctival hemorrhages, chemosis, eyelid swelling 4

Bacterial Conjunctivitis

• Mucopurulent discharge with matted eyelids on waking 3, 5
• Papillary rather than follicular reaction 3
• Can be unilateral or bilateral 4
• May have concurrent otitis media, sinusitis, or pharyngitis in children 4

Allergic Conjunctivitis

• Itching as the most consistent distinguishing feature 2, 3
• Bilateral presentation with watery discharge and mild mucous component 3
• Eyelid edema, periorbital hyperpigmentation 3
• Absence of preauricular lymphadenopathy 3

High-Risk Forms Requiring Urgent Recognition

Gonococcal conjunctivitis: Marked eyelid edema, severe hyperpurulent discharge, rapid progression, risk of corneal perforation 2, 3, 4

HSV conjunctivitis: Usually unilateral, vesicular rash or ulceration of eyelids, dendritic epithelial keratitis 4

Chlamydial conjunctivitis: Follicular reaction in adults (no follicles in neonates), requires systemic treatment and partner evaluation 3, 4

Critical Red Flags Requiring Immediate Ophthalmology Referral

Refer urgently for any of the following:

• Visual loss or decreased vision 2, 3
• Moderate or severe pain 2, 3
• Severe purulent discharge 2, 3
• Corneal involvement 2, 3
• Conjunctival scarring 2, 3
• Lack of response to therapy after 3-4 days 2
• Recurrent episodes 2, 3
• History of HSV eye disease 2, 3
• Immunocompromised status 2, 3
• Recent ocular surgery 3
• Vesicular rash on eyelids or nose 3
• Neonatal conjunctivitis 4

Common Diagnostic Pitfalls

Avoid indiscriminate use of topical antibiotics or corticosteroids, which may cause unnecessary adverse effects and delay diagnosis of underlying conditions. 3, 4

Chronic and/or recalcitrant conjunctivitis may indicate underlying malignancy (sebaceous or squamous cell carcinoma) and requires further evaluation. 4

Dry eye and blepharitis are the most frequent causes of conjunctival inflammation and require treatment directed at the underlying problem rather than the conjunctivitis itself. 3

Never use topical corticosteroids in suspected HSV without antiviral coverage, as they potentiate HSV infection. 2

Failure to consider sexual abuse in children with gonococcal or chlamydial conjunctivitis is a critical oversight. 2