Conjunctivitis

Conjunctivitis is inflammation of the conjunctiva and is one of the most common causes of the red eye. It is most often viral in etiology and typically self-limited, but certain forms (gonococcal, herpetic) can threaten vision if not treated aggressively.

Etiology

Category	Common Causes
Viral	Adenovirus (most common), HSV, enterovirus
Bacterial	Staphylococcus, Streptococcus, H. influenzae, N. gonorrhoeae, Chlamydia
Allergic	Seasonal/perennial allergens, atopic keratoconjunctivitis
Other	Toxic/chemical irritation, parasitic, fungal

Keratoconjunctivitis = conjunctivitis with corneal involvement (punctate ulcerations).

1. Bacterial Conjunctivitis

Clinical features:

Painless mucopurulent discharge — hallmark finding
Eyelids stuck together on awakening
Unilateral or bilateral conjunctival injection
Clear cornea (no fluorescein uptake unless abrasion/ulcer)
Chemosis (conjunctival edema) common
Preauricular lymphadenopathy usually absent (except in gonococcal)

Bacterial conjunctivitis — mucopurulent discharge, conjunctival injection, and lid edema (H. influenzae)

Bacterial conjunctivitis with mucopurulent discharge and conjunctival injection

Typical pathogens: Staphylococcus spp., Streptococcus spp., H. influenzae

Treatment:

Cases are often self-limited; antibiotics shorten the course
Trimethoprim–polymyxin B — first-line (avoids sulfa/neomycin allergy risk)
Fluoroquinolone (besifloxacin, moxifloxacin, levofloxacin) or tobramycin — for contact lens wearers (cover Pseudomonas)
Avoid gentamicin ophthalmic (high ocular irritation)
Always perform fluorescein stain of the cornea (especially in infants) to exclude corneal abrasion, ulcer, or herpetic dendrite

Special cases:

Gonococcal conjunctivitis — hyperacute, copious purulent discharge, preauricular LAD; cause of ophthalmia neonatorum; requires urgent systemic treatment
Chlamydial conjunctivitis — chronic follicular conjunctivitis; also causes neonatal disease

2. Viral Conjunctivitis

Clinical features:

Often preceded by upper respiratory infection
Watery discharge (not purulent)
Mild to moderate "red eye," no eye pain unless keratitis present
Starts unilateral, second eye involved within days
Preauricular lymphadenopathy — characteristic (distinguishes from bacterial)
Slit lamp: follicles on inferior palpebral conjunctiva
Occasional small subconjunctival hemorrhages

Viral conjunctivitis — bilateral conjunctival injection and watery discharge

Bilateral viral conjunctivitis with conjunctival injection and watery discharge

Epidemic Keratoconjunctivitis (EKC):

Caused by adenovirus (types 8, 19, 37 — Group D HAdV)
More severe; may be preceded by fever, myalgias, malaise
Highly contagious; tends to occur in epidemics
Fluorescein stain shows punctate keratitis
Common findings: conjunctival injection (91%), tearing (80%), follicular reaction (76%), petechiae (70%), foreign body sensation (67%)

Treatment:

Supportive: cool compresses, artificial tears (5–6×/day)
Ocular decongestants (e.g., Naphcon-A, 1 drop TID PRN)
Course: 1–3 weeks
Highly contagious: frequent handwashing, separate towels, disinfect slit lamp/exam chair
Always examine the cornea with fluorescein to exclude herpetic dendrite

3. Allergic Conjunctivitis

Clinical features:

Itching — dominant symptom (distinguishes from bacterial/viral)
Watery discharge, redness
Erythematous, swollen eyelids
Conjunctival injection with papillae (irregular mounds with central vascular tuft) on inferior fornix
Prominent chemosis may be present

Allergic conjunctivitis — prominent chemosis of lower palpebral conjunctiva

Prominent chemosis in allergic conjunctivitis

Treatment (stepped by severity):

Severity	Treatment
Mild	Artificial tears alone; identify/eliminate allergen
Moderate	Topical antihistamine/decongestant, mast cell stabilizers, or NSAIDs; cool compresses QID
Severe	Topical steroids (consult ophthalmologist first — occult herpetic infection must be excluded)

Key Differentiating Features

Feature	Bacterial	Viral	Allergic
Discharge	Mucopurulent	Watery	Watery
Itching	Absent	Absent/mild	Dominant
Preauricular LAD	Absent (except GC)	Present	Absent
Eyelids stuck	Yes (morning)	No	No
Conjunctival reaction	Papillae	Follicles	Papillae
Cornea	Clear	± Punctate keratitis	Clear
Bilaterality	Can be bilateral	Starts unilateral	Bilateral

When to Refer Urgently

Suspected gonococcal infection (hyperacute, copious discharge)
Corneal involvement (reduced VA, fluorescein uptake, herpetic dendrite)
Neonatal conjunctivitis (ophthalmia neonatorum)
Failure to improve or diagnosis uncertain after initial assessment

— Tintinalli's Emergency Medicine, p. 1582–1583

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